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The ACPI GPE wakeup from suspend-to-idle is currently based on using
the IRQF_NO_SUSPEND flag for the ACPI SCI, but that is problematic
for a couple of reasons. First, in principle the ACPI SCI may be
shared and IRQF_NO_SUSPEND does not really work well with shared
interrupts. Second, it may require the ACPI subsystem to special-case
the handling of device notifications depending on whether or not
they are received during suspend-to-idle in some places which would
lead to fragile code. Finally, it's better the handle ACPI wakeup
interrupts consistently with wakeup interrupts from other sources.
For this reason, remove the IRQF_NO_SUSPEND flag from the ACPI SCI
and use enable_irq_wake()/disable_irq_wake() with it instead, which
requires two additional platform hooks to be added to struct
platform_freeze_ops.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Subsequent change sets will add platform-related operations between
dpm_suspend_late() and dpm_suspend_noirq() as well as between
dpm_resume_noirq() and dpm_resume_early() in suspend_enter(), so
export these functions for suspend_enter() to be able to call them
separately and split the invocations of dpm_suspend_end() and
dpm_resume_start() in there accordingly.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Add a routine for host OSes to enable all wakeup GPEs and disable
all of the non-wakeup ones at the same time.
It will be used for the handling of GPE wakeup from suspend-to-idle
in Linux.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Eric Dumazet noticed that all no-nonexthop or no-gateway routes which
are already marked DST_HOST (e.g. input routes routes) will always be
invalidated during sk_dst_check. Thus per-socket dst caching absolutely
had no effect and early demuxing had no effect.
Thus this patch removes rt6i_genid: fn_sernum already gets modified during
add operations, so we only must ensure we mutate fn_sernum during ipv6
address remove operations. This is a fairly cost extensive operations,
but address removal should not happen that often. Also our mtu update
functions do the same and we heard no complains so far. xfrm policy
changes also cause a call into fib6_flush_trees. Also plug a hole in
rt6_info (no cacheline changes).
I verified via tracing that this change has effect.
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: YOSHIFUJI Hideaki <hideaki@yoshifuji.org>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Cc: Martin Lau <kafai@fb.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This driver is used by the bcm53xx ARM SoC code. Now it is possible to
give the address of the chipcommon core in device tree and bcma will
search for all the other cores.
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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Some architectures do not have a simple view of the PCI I/O space and
instead use a range of CPU addresses that map to bus addresses. For some
architectures these ranges will be expressed by OF bindings in a device
tree file.
This patch introduces a pci_register_io_range() helper function with a
generic implementation that can be used by such architectures to keep track
of the I/O ranges described by the PCI bindings. If the PCI_IOBASE macro
is not defined, that signals lack of support for PCI and we return an
error.
In order to retrieve the CPU address associated with an I/O port, a new
helper function pci_pio_to_address() is introduced. This will search in
the list of ranges registered with pci_register_io_range() and return the
CPU address that corresponds to the given port.
[arnd: add dummy !CONFIG_OF pci_pio_to_address() to fix build errors]
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
CC: Grant Likely <grant.likely@linaro.org>
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The !CONFIG_GENERIC_IOMAP version of ioport_map() is wrong. It returns a
mapped, i.e., virtual, address that can start from zero and completely
ignores the PCI_IOBASE and IO_SPACE_LIMIT that most architectures that use
!CONFIG_GENERIC_MAP define.
Tested-by: Tanmay Inamdar <tinamdar@apm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
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Commit 1abf635 (scsi: use 64-bit value for 'max_luns') changed the order
of Scsi_Host members. Update the comment to reflect this.
Signed-off-by: Sebastian Herbszt <herbszt@gmx.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
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'regulator/topic/tps65910' and 'regulator/topic/voltage-ev' into regulator-next
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'regulator/topic/rn5t618' and 'regulator/topic/samsung' into regulator-next
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'regulator/topic/max77802' and 'regulator/topic/of' into regulator-next
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'regulator/topic/enable', 'regulator/topic/fan53555', 'regulator/topic/hi6421' and 'regulator/topic/isl9305' into regulator-next
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'regulator/topic/axp20x', 'regulator/topic/bcm590xx' and 'regulator/topic/da9211' into regulator-next
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This allows importing reservation objects from dma-bufs.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
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Allows importing dma_reservation_objects from a dma-buf.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/tfiga/samsung-clk into clk-next
Samsung clock patches for v3.18
1) non-critical fixes (without the need to push to stable)
fa0111be4ff3 clk: samsung: exynos4: remove duplicate div_core2 divider clock instantiation
b511593d7165 clk: samsung: exynos4: fix g3d clocks
c14254300131 clk: samsung: exynos4: add missing smmu_g2d clock and update comments
22842d244af3 clk: samsung: exynos5260: fix typo in clock name
e82ba578ccde clk: samsung: exynos3250: fix width field of mout_mmc0/1
59037b92f440 clk: samsung: exynos3250: fix width and shift of div_spi0_isp clock
5ce37f266650 clk: samsung: exynos3250: fix mout_cam_blk parent list
2) Clock driver extensions
07ccf02ba5c3 dt-bindings: clk: samsung: Document the DMC domain of Exynos3250 CMU
d0e73eaf1925 ARM: dts: exynos3250: Add CMU node for DMC domain clocks
e3c3f19bc618 clk: samsung: exynos3250: Register DMC clk provider
4676f0aab9dc clk: samsung: exynos4: add support for MOUT_HDMI and MOUT_MIXER clocks
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clk-next
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In <https://lkml.org/lkml/2014/6/10/265> pointed out that the 10-bit
flag in the cros_ec_tunnel was useless. It went into a 16-bit flags
field but was defined at (1 << 16).
Since we have no 10-bit i2c devices on the other side of the tunnel on
any known devices this was never a problem. Until we do it makes
sense to remove this code. On the EC side the code to handle this
flag was removed in <https://chromium-review.googlesource.com/204162>.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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After previous patches to simplify qstats the qstats can be
made per cpu with a packed union in Qdisc struct.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This removes the use of qstats->qlen variable from the classifiers
and makes it an explicit argument to gnet_stats_copy_queue().
The qlen represents the qdisc queue length and is packed into
the qstats at the last moment before passnig to user space. By
handling it explicitely we avoid, in the percpu stats case, having
to figure out which per_cpu variable to put it in.
It would probably be best to remove it from qstats completely
but qstats is a user space ABI and can't be broken. A future
patch could make an internal only qstats structure that would
avoid having to allocate an additional u32 variable on the
Qdisc struct. This would make the qstats struct 128bits instead
of 128+32.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This adds helpers to manipulate qstats logic and replaces locations
that touch the counters directly. This simplifies future patches
to push qstats onto per cpu counters.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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In order to run qdisc's without locking statistics and estimators
need to be handled correctly.
To resolve bstats make the statistics per cpu. And because this is
only needed for qdiscs that are running without locks which is not
the case for most qdiscs in the near future only create percpu
stats when qdiscs set the TCQ_F_CPUSTATS flag.
Next because estimators use the bstats to calculate packets per
second and bytes per second the estimator code paths are updated
to use the per cpu statistics.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The kbuild test robot wrote me:
| make.cross ARCH=powerpc
|>> ERROR: ".__xchg_called_with_bad_pointer" [drivers/tty/serial/8250/8250.ko] undefined!
The generic implementation of xchg() on arm and x86 works for variables of
size one bye (char). According to the report powerpc does not support
xchg() for one byte sized variables and looking further it seems also to
be the same case for sparc and tile (or for 10 out of 26 architectures
which provide a custom implementation).
For that reason I increase the size of the variable from one to four
bytes to get it work on powerpc (and the others).
Reported-By: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The commit 46420dd73b80 (PM / Domains: Add APIs to attach/detach a PM
domain for a device) started using errno values in pm.h header file.
It also failed to include the header for these, thus it caused
compiler errors.
Instead of including the errno header to pm.h, let's move the functions
to pm_domain.h, since it's a better match.
Fixes: 46420dd73b80 (PM / Domains: Add APIs to attach/detach a PM domain for a device)
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Use the platform data to set the clk_freq when there is no DT configuration
available. The clk_freq in turn will determine the I2C speed mode.
In Quark, there is currently no other configuration mechanism other than
board files.
Signed-off-by: Raymond Tan <raymond.tan@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Hock Leong Kweh <hock.leong.kweh@intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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This patch adds a new mode of operation to macvlan, called "source".
It allows one to set a list of allowed mac address, which is used
to match against source mac address from received frames on underlying
interface.
This enables creating mac based VLAN associations, instead of standard
port or tag based. The feature is useful to deploy 802.1x mac based
behavior, where drivers of underlying interfaces doesn't allows that.
Configuration is done through the netlink interface using e.g.:
ip link add link eth0 name macvlan0 type macvlan mode source
ip link add link eth0 name macvlan1 type macvlan mode source
ip link set link dev macvlan0 type macvlan macaddr add 00:11:11:11:11:11
ip link set link dev macvlan0 type macvlan macaddr add 00:22:22:22:22:22
ip link set link dev macvlan0 type macvlan macaddr add 00:33:33:33:33:33
ip link set link dev macvlan1 type macvlan macaddr add 00:33:33:33:33:33
ip link set link dev macvlan1 type macvlan macaddr add 00:44:44:44:44:44
This allows clients with MAC addresses 00:11:11:11:11:11,
00:22:22:22:22:22 to be part of only VLAN associated with macvlan0
interface. Clients with MAC addresses 00:44:44:44:44:44 with only VLAN
associated with macvlan1 interface. And client with MAC address
00:33:33:33:33:33 to be associated with both VLANs.
Based on work of Stefan Gula <steweg@gmail.com>
v8: last version of Stefan Gula for Kernel 3.2.1
v9: rework onto linux-next 2014-03-12 by Michael Braun
add MACADDR_SET command, enable to configure mac for source mode
while creating interface
v10:
- reduce indention level
- rename source_list to source_entry
- use aligned 64bit ether address
- use hash_64 instead of addr[5]
v11:
- rebase for 3.14 / linux-next 20.04.2014
v12
- rebase for linux-next 2014-09-25
Signed-off-by: Michael Braun <michael-dev@fami-braun.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Pablo Neira Ayuso says:
====================
pull request: netfilter/ipvs updates for net-next
The following patchset contains Netfilter/IPVS updates for net-next,
most relevantly they are:
1) Four patches to make the new nf_tables masquerading support
independent of the x_tables infrastructure. This also resolves a
compilation breakage if the masquerade target is disabled but the
nf_tables masq expression is enabled.
2) ipset updates via Jozsef Kadlecsik. This includes the addition of the
skbinfo extension that allows you to store packet metainformation in the
elements. This can be used to fetch and restore this to the packets through
the iptables SET target, patches from Anton Danilov.
3) Add the hash:mac set type to ipset, from Jozsef Kadlecsick.
4) Add simple weighted fail-over scheduler via Simon Horman. This provides
a fail-over IPVS scheduler (unlike existing load balancing schedulers).
Connections are directed to the appropriate server based solely on
highest weight value and server availability, patch from Kenny Mathis.
5) Support IPv6 real servers in IPv4 virtual-services and vice versa.
Simon Horman informs that the motivation for this is to allow more
flexibility in the choice of IP version offered by both virtual-servers
and real-servers as they no longer need to match: An IPv4 connection
from an end-user may be forwarded to a real-server using IPv6 and
vice versa. No ip_vs_sync support yet though. Patches from Alex Gartrell
and Julian Anastasov.
6) Add global generation ID to the nf_tables ruleset. When dumping from
several different object lists, we need a way to identify that an update
has ocurred so userspace knows that it needs to refresh its lists. This
also includes a new command to obtain the 32-bits generation ID. The
less significant 16-bits of this ID is also exposed through res_id field
in the nfnetlink header to quickly detect the interference and retry when
there is no risk of ID wraparound.
7) Move br_netfilter out of the bridge core. The br_netfilter code is
built in the bridge core by default. This causes problems of different
kind to people that don't want this: Jesper reported performance drop due
to the inconditional hook registration and I remember to have read complains
on netdev from people regarding the unexpected behaviour of our bridging
stack when br_netfilter is enabled (fragmentation handling, layer 3 and
upper inspection). People that still need this should easily undo the
damage by modprobing the new br_netfilter module.
8) Dump the set policy nf_tables that allows set parameterization. So
userspace can keep user-defined preferences when saving the ruleset.
From Arturo Borrero.
9) Use __seq_open_private() helper function to reduce boiler plate code
in x_tables, From Rob Jones.
10) Safer default behaviour in case that you forget to load the protocol
tracker. Daniel Borkmann and Florian Westphal detected that if your
ruleset is stateful, you allow traffic to at least one single SCTP port
and the SCTP protocol tracker is not loaded, then any SCTP traffic may
be pass through unfiltered. After this patch, the connection tracking
classifies SCTP/DCCP/UDPlite/GRE packets as invalid if your kernel has
been compiled with support for these modules.
====================
Trivially resolved conflict in include/linux/skbuff.h, Eric moved some
netfilter skbuff members around, and the netfilter tree adjusted the
ifdef guards for the bridging info pointer.
Signed-off-by: David S. Miller <davem@davemloft.net>
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Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
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After Octavian Purdilas tcp ipv4/ipv6 unification work this helper only
has a single callsite.
While at it, convert name to lowercase, suggested by Stephen.
Suggested-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The com20020-pci driver is currently designed to instance
one netdev with one pci device. This patch adds support to
instance many cards with one pci device, depending on the device
data in the private data.
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This patch adds metadata for the com20020 to prepare for devices with
multiple io address areas with multi card interfaces.
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This patch adds server support for the NFS v4.2 operation SEEK, which
returns the position of the next hole or data segment in a file.
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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It's cleaner to introduce everything at once and have the server reply
with "not supported" than it would be to introduce extra operations when
implementing a specific one in the middle of the list.
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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The only remaining user of the CODEC pointer in the DAPM struct is to
initialize the CODEC pointer in the widget struct. The later is scheduled
for removal, but has still a few users left. For now use
dapm->component->codec to initialize it.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
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With proliferation of bit fields in sk_buff, __copy_skb_header() became
quite expensive, showing as the most expensive function in a GSO
workload.
__copy_skb_header() performance is also critical for non GSO TCP
operations, as it is used from skb_clone()
This patch carefully moves all the fields that were not copied in a
separate zone : cloned, nohdr, fclone, peeked, head_frag, xmit_more
Then I moved all other fields and all other copied fields in a section
delimited by headers_start[0]/headers_end[0] section so that we
can use a single memcpy() call, inlined by compiler using long
word load/stores.
I also tried to make all copies in the natural orders of sk_buff,
to help hardware prefetching.
I made sure sk_buff size did not change.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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VFIO allows devices to be safely handed off to userspace by putting
them behind an IOMMU configured to ensure DMA and interrupt isolation.
This enables userspace KVM clients, such as kvmtool and qemu, to further
map the device into a virtual machine.
With IOMMUs such as the ARM SMMU, it is then possible to provide SMMU
translation services to the guest operating system, which are nested
with the existing translation installed by VFIO. However, enabling this
feature means that the IOMMU driver must be informed that the VFIO domain
is being created for the purposes of nested translation.
This patch adds a new IOMMU type (VFIO_TYPE1_NESTING_IOMMU) to the VFIO
type-1 driver. The new IOMMU type acts identically to the
VFIO_TYPE1v2_IOMMU type, but additionally sets the DOMAIN_ATTR_NESTING
attribute on its IOMMU domains.
Cc: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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Some IOMMUs, such as the ARM SMMU, support two stages of translation.
The idea behind such a scheme is to allow a guest operating system to
use the IOMMU for DMA mappings in the first stage of translation, with
the hypervisor then installing mappings in the second stage to provide
isolation of the DMA to the physical range assigned to that virtual
machine.
In order to allow IOMMU domains to be used for second-stage translation,
this patch adds a new iommu_attr (IOMMU_ATTR_NESTING) for setting
second-stage domains prior to device attach. The attribute can also be
queried to see if a domain is actually making use of nesting.
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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Remove inclusion of linux/pci.h in mei layer
however we need to include the headers that before
got included implicitly from linux/pci.h.
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Add the generic PHY support, analogous to the USB PHY support. Intended it to be
used with the PCI EHCI/OHCI drivers and the xHCI platform driver.
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The USB PHY member of the HCD structure is renamed to 'usb_phy' and
modifications are done in all drivers accessing it.
This is in preparation to adding the generic PHY support.
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
[Sergei: added missing 'drivers/usb/misc/lvstest.c' file, resolved rejects,
updated changelog.]
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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We want to know in which cases the user explicitly sets the policy
options. In that case, we also want to dump back the info.
Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Previously, the TI clock driver initialized all the clocks hierarchically
under each separate clock provider node. Now, each clock that requires
IO access will instead check their parent node to find out which IO range
to use.
This patch allows the TI clock driver to use a few new features provided
by the generic of_clk_init, and also allows registration of clock nodes
outside the clock hierarchy (for example, any external clocks.)
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Jyri Sarha <jsarha@ti.com>
Cc: Stefan Assmann <sassmann@kpanic.de>
Acked-by: Tony Lindgren <tony@atomide.com>
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This work adds the DataCenter TCP (DCTCP) congestion control
algorithm [1], which has been first published at SIGCOMM 2010 [2],
resp. follow-up analysis at SIGMETRICS 2011 [3] (and also, more
recently as an informational IETF draft available at [4]).
DCTCP is an enhancement to the TCP congestion control algorithm for
data center networks. Typical data center workloads are i.e.
i) partition/aggregate (queries; bursty, delay sensitive), ii) short
messages e.g. 50KB-1MB (for coordination and control state; delay
sensitive), and iii) large flows e.g. 1MB-100MB (data update;
throughput sensitive). DCTCP has therefore been designed for such
environments to provide/achieve the following three requirements:
* High burst tolerance (incast due to partition/aggregate)
* Low latency (short flows, queries)
* High throughput (continuous data updates, large file
transfers) with commodity, shallow buffered switches
The basic idea of its design consists of two fundamentals: i) on the
switch side, packets are being marked when its internal queue
length > threshold K (K is chosen so that a large enough headroom
for marked traffic is still available in the switch queue); ii) the
sender/host side maintains a moving average of the fraction of marked
packets, so each RTT, F is being updated as follows:
F := X / Y, where X is # of marked ACKs, Y is total # of ACKs
alpha := (1 - g) * alpha + g * F, where g is a smoothing constant
The resulting alpha (iow: probability that switch queue is congested)
is then being used in order to adaptively decrease the congestion
window W:
W := (1 - (alpha / 2)) * W
The means for receiving marked packets resp. marking them on switch
side in DCTCP is the use of ECN.
RFC3168 describes a mechanism for using Explicit Congestion Notification
from the switch for early detection of congestion, rather than waiting
for segment loss to occur.
However, this method only detects the presence of congestion, not
the *extent*. In the presence of mild congestion, it reduces the TCP
congestion window too aggressively and unnecessarily affects the
throughput of long flows [4].
DCTCP, as mentioned, enhances Explicit Congestion Notification (ECN)
processing to estimate the fraction of bytes that encounter congestion,
rather than simply detecting that some congestion has occurred. DCTCP
then scales the TCP congestion window based on this estimate [4],
thus it can derive multibit feedback from the information present in
the single-bit sequence of marks in its control law. And thus act in
*proportion* to the extent of congestion, not its *presence*.
Switches therefore set the Congestion Experienced (CE) codepoint in
packets when internal queue lengths exceed threshold K. Resulting,
DCTCP delivers the same or better throughput than normal TCP, while
using 90% less buffer space.
It was found in [2] that DCTCP enables the applications to handle 10x
the current background traffic, without impacting foreground traffic.
Moreover, a 10x increase in foreground traffic did not cause any
timeouts, and thus largely eliminates TCP incast collapse problems.
The algorithm itself has already seen deployments in large production
data centers since then.
We did a long-term stress-test and analysis in a data center, short
summary of our TCP incast tests with iperf compared to cubic:
This test measured DCTCP throughput and latency and compared it with
CUBIC throughput and latency for an incast scenario. In this test, 19
senders sent at maximum rate to a single receiver. The receiver simply
ran iperf -s.
The senders ran iperf -c <receiver> -t 30. All senders started
simultaneously (using local clocks synchronized by ntp).
This test was repeated multiple times. Below shows the results from a
single test. Other tests are similar. (DCTCP results were extremely
consistent, CUBIC results show some variance induced by the TCP timeouts
that CUBIC encountered.)
For this test, we report statistics on the number of TCP timeouts,
flow throughput, and traffic latency.
1) Timeouts (total over all flows, and per flow summaries):
CUBIC DCTCP
Total 3227 25
Mean 169.842 1.316
Median 183 1
Max 207 5
Min 123 0
Stddev 28.991 1.600
Timeout data is taken by measuring the net change in netstat -s
"other TCP timeouts" reported. As a result, the timeout measurements
above are not restricted to the test traffic, and we believe that it
is likely that all of the "DCTCP timeouts" are actually timeouts for
non-test traffic. We report them nevertheless. CUBIC will also include
some non-test timeouts, but they are drawfed by bona fide test traffic
timeouts for CUBIC. Clearly DCTCP does an excellent job of preventing
TCP timeouts. DCTCP reduces timeouts by at least two orders of
magnitude and may well have eliminated them in this scenario.
2) Throughput (per flow in Mbps):
CUBIC DCTCP
Mean 521.684 521.895
Median 464 523
Max 776 527
Min 403 519
Stddev 105.891 2.601
Fairness 0.962 0.999
Throughput data was simply the average throughput for each flow
reported by iperf. By avoiding TCP timeouts, DCTCP is able to
achieve much better per-flow results. In CUBIC, many flows
experience TCP timeouts which makes flow throughput unpredictable and
unfair. DCTCP, on the other hand, provides very clean predictable
throughput without incurring TCP timeouts. Thus, the standard deviation
of CUBIC throughput is dramatically higher than the standard deviation
of DCTCP throughput.
Mean throughput is nearly identical because even though cubic flows
suffer TCP timeouts, other flows will step in and fill the unused
bandwidth. Note that this test is something of a best case scenario
for incast under CUBIC: it allows other flows to fill in for flows
experiencing a timeout. Under situations where the receiver is issuing
requests and then waiting for all flows to complete, flows cannot fill
in for timed out flows and throughput will drop dramatically.
3) Latency (in ms):
CUBIC DCTCP
Mean 4.0088 0.04219
Median 4.055 0.0395
Max 4.2 0.085
Min 3.32 0.028
Stddev 0.1666 0.01064
Latency for each protocol was computed by running "ping -i 0.2
<receiver>" from a single sender to the receiver during the incast
test. For DCTCP, "ping -Q 0x6 -i 0.2 <receiver>" was used to ensure
that traffic traversed the DCTCP queue and was not dropped when the
queue size was greater than the marking threshold. The summary
statistics above are over all ping metrics measured between the single
sender, receiver pair.
The latency results for this test show a dramatic difference between
CUBIC and DCTCP. CUBIC intentionally overflows the switch buffer
which incurs the maximum queue latency (more buffer memory will lead
to high latency.) DCTCP, on the other hand, deliberately attempts to
keep queue occupancy low. The result is a two orders of magnitude
reduction of latency with DCTCP - even with a switch with relatively
little RAM. Switches with larger amounts of RAM will incur increasing
amounts of latency for CUBIC, but not for DCTCP.
4) Convergence and stability test:
This test measured the time that DCTCP took to fairly redistribute
bandwidth when a new flow commences. It also measured DCTCP's ability
to remain stable at a fair bandwidth distribution. DCTCP is compared
with CUBIC for this test.
At the commencement of this test, a single flow is sending at maximum
rate (near 10 Gbps) to a single receiver. One second after that first
flow commences, a new flow from a distinct server begins sending to
the same receiver as the first flow. After the second flow has sent
data for 10 seconds, the second flow is terminated. The first flow
sends for an additional second. Ideally, the bandwidth would be evenly
shared as soon as the second flow starts, and recover as soon as it
stops.
The results of this test are shown below. Note that the flow bandwidth
for the two flows was measured near the same time, but not
simultaneously.
DCTCP performs nearly perfectly within the measurement limitations
of this test: bandwidth is quickly distributed fairly between the two
flows, remains stable throughout the duration of the test, and
recovers quickly. CUBIC, in contrast, is slow to divide the bandwidth
fairly, and has trouble remaining stable.
CUBIC DCTCP
Seconds Flow 1 Flow 2 Seconds Flow 1 Flow 2
0 9.93 0 0 9.92 0
0.5 9.87 0 0.5 9.86 0
1 8.73 2.25 1 6.46 4.88
1.5 7.29 2.8 1.5 4.9 4.99
2 6.96 3.1 2 4.92 4.94
2.5 6.67 3.34 2.5 4.93 5
3 6.39 3.57 3 4.92 4.99
3.5 6.24 3.75 3.5 4.94 4.74
4 6 3.94 4 5.34 4.71
4.5 5.88 4.09 4.5 4.99 4.97
5 5.27 4.98 5 4.83 5.01
5.5 4.93 5.04 5.5 4.89 4.99
6 4.9 4.99 6 4.92 5.04
6.5 4.93 5.1 6.5 4.91 4.97
7 4.28 5.8 7 4.97 4.97
7.5 4.62 4.91 7.5 4.99 4.82
8 5.05 4.45 8 5.16 4.76
8.5 5.93 4.09 8.5 4.94 4.98
9 5.73 4.2 9 4.92 5.02
9.5 5.62 4.32 9.5 4.87 5.03
10 6.12 3.2 10 4.91 5.01
10.5 6.91 3.11 10.5 4.87 5.04
11 8.48 0 11 8.49 4.94
11.5 9.87 0 11.5 9.9 0
SYN/ACK ECT test:
This test demonstrates the importance of ECT on SYN and SYN-ACK packets
by measuring the connection probability in the presence of competing
flows for a DCTCP connection attempt *without* ECT in the SYN packet.
The test was repeated five times for each number of competing flows.
Competing Flows 1 | 2 | 4 | 8 | 16
------------------------------
Mean Connection Probability 1 | 0.67 | 0.45 | 0.28 | 0
Median Connection Probability 1 | 0.65 | 0.45 | 0.25 | 0
As the number of competing flows moves beyond 1, the connection
probability drops rapidly.
Enabling DCTCP with this patch requires the following steps:
DCTCP must be running both on the sender and receiver side in your
data center, i.e.:
sysctl -w net.ipv4.tcp_congestion_control=dctcp
Also, ECN functionality must be enabled on all switches in your
data center for DCTCP to work. The default ECN marking threshold (K)
heuristic on the switch for DCTCP is e.g., 20 packets (30KB) at
1Gbps, and 65 packets (~100KB) at 10Gbps (K > 1/7 * C * RTT, [4]).
In above tests, for each switch port, traffic was segregated into two
queues. For any packet with a DSCP of 0x01 - or equivalently a TOS of
0x04 - the packet was placed into the DCTCP queue. All other packets
were placed into the default drop-tail queue. For the DCTCP queue,
RED/ECN marking was enabled, here, with a marking threshold of 75 KB.
More details however, we refer you to the paper [2] under section 3).
There are no code changes required to applications running in user
space. DCTCP has been implemented in full *isolation* of the rest of
the TCP code as its own congestion control module, so that it can run
without a need to expose code to the core of the TCP stack, and thus
nothing changes for non-DCTCP users.
Changes in the CA framework code are minimal, and DCTCP algorithm
operates on mechanisms that are already available in most Silicon.
The gain (dctcp_shift_g) is currently a fixed constant (1/16) from
the paper, but we leave the option that it can be chosen carefully
to a different value by the user.
In case DCTCP is being used and ECN support on peer site is off,
DCTCP falls back after 3WHS to operate in normal TCP Reno mode.
ss {-4,-6} -t -i diag interface:
... dctcp wscale:7,7 rto:203 rtt:2.349/0.026 mss:1448 cwnd:2054
ssthresh:1102 ce_state 0 alpha 15 ab_ecn 0 ab_tot 735584
send 10129.2Mbps pacing_rate 20254.1Mbps unacked:1822 retrans:0/15
reordering:101 rcv_space:29200
... dctcp-reno wscale:7,7 rto:201 rtt:0.711/1.327 ato:40 mss:1448
cwnd:10 ssthresh:1102 fallback_mode send 162.9Mbps pacing_rate
325.5Mbps rcv_rtt:1.5 rcv_space:29200
More information about DCTCP can be found in [1-4].
[1] http://simula.stanford.edu/~alizade/Site/DCTCP.html
[2] http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf
[3] http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp_analysis-full.pdf
[4] http://tools.ietf.org/html/draft-bensley-tcpm-dctcp-00
Joint work with Florian Westphal and Glenn Judd.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Glenn Judd <glenn.judd@morganstanley.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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DataCenter TCP (DCTCP) determines cwnd growth based on ECN information
and ACK properties, e.g. ACK that updates window is treated differently
than DUPACK.
Also DCTCP needs information whether ACK was delayed ACK. Furthermore,
DCTCP also implements a CE state machine that keeps track of CE markings
of incoming packets.
Therefore, extend the congestion control framework to provide these
event types, so that DCTCP can be properly implemented as a normal
congestion algorithm module outside of the core stack.
Joint work with Daniel Borkmann and Glenn Judd.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Glenn Judd <glenn.judd@morganstanley.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The congestion control ops "cwnd_event" currently supports
CA_EVENT_FAST_ACK and CA_EVENT_SLOW_ACK events (among others).
Both FAST and SLOW_ACK are only used by Westwood congestion
control algorithm.
This removes both flags from cwnd_event and adds a new
in_ack_event callback for this. The goal is to be able to
provide more detailed information about ACKs, such as whether
ECE flag was set, or whether the ACK resulted in a window
update.
It is required for DataCenter TCP (DCTCP) congestion control
algorithm as it makes a different choice depending on ECE being
set or not.
Joint work with Daniel Borkmann and Glenn Judd.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Glenn Judd <glenn.judd@morganstanley.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This patch adds a flag to TCP congestion algorithms that allows
for requesting to mark IPv4/IPv6 sockets with transport as ECN
capable, that is, ECT(0), when required by a congestion algorithm.
It is currently used and needed in DataCenter TCP (DCTCP), as it
requires both peers to assert ECT on all IP packets sent - it
uses ECN feedback (i.e. CE, Congestion Encountered information)
from switches inside the data center to derive feedback to the
end hosts.
Therefore, simply add a new flag to icsk_ca_ops. Note that DCTCP's
algorithm/behaviour slightly diverges from RFC3168, therefore this
is only (!) enabled iff the assigned congestion control ops module
has requested this. By that, we can tightly couple this logic really
only to the provided congestion control ops.
Joint work with Florian Westphal and Glenn Judd.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Glenn Judd <glenn.judd@morganstanley.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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