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Some platforms gate the pclk (APB - the bus - clock) to the peripherals
for power saving, along with the functional clock. When devices are
accessed without pclk enabled, the kernel will oops.
This gives them two options:
1. Leave all clocks on all the time.
2. Attempt to gate pclk along with the functional clock.
(With some hardware, pclk and the functional clock are gated by a single
bit in a register.)
(1) has the disadvantage that it causes increased power usage, which is
bad news for battery operated devices. (2) can lead to kernel oops if
registers are accessed without the functional clock being enabled.
So, introduce the apb_pclk signal in such a way existing drivers don't
need to be updated. Essentially, this means we guarantee that:
1. pclk will be enabled whenever the driver is bound to a device -
from probe() to remove() time.
2. pclk will also be enabled when reading the primecell IDs from the device.
In order to allow drivers to be incrementally updated to achieve greater
power savings, we provide two additional calls to allow drivers to
manage the pclk - amba_pclk_enable()/amba_pclk_disable().
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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linux/amba/bus.h have dependencies on linux/device.h and linux/resource.h, but
it doesn't include them. We get compilation errors in our files which include
bus.h but doesn't include device.h and resource.h. This patch includes device.h
and resource.h in linux/amba/bus.h file.
Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Acked-by: Linux Walleij <linux.ml.walleij@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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This fixes the filepath encoded in <linux/amba/bus.h> and adds
some documentation as to what this bus really means.
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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This moves the primecell vendor enum definition inside vic.c
out to linux/amba/bus.h where it belongs and replace any
occurances of specific vendor ID:s with the respective enums
instead.
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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The second argument of the probe method points to the amba_id
structure, so it's better passed with the correct type. None of the
current in-tree drivers uses the pointer, so they have only been
checked for a clean compile.
Change suggested by Russell King.
Signed-off-by: Alessandro Rubini <rubini@unipv.it>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Since the ARM AMBA bus is used on MIPS as well as ARM, we need
to make the bus available for other architectures to use. Move
the AMBA include files from include/asm-arm/hardware/ to
include/linux/amba/
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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