From 6748dcc269e52925993e0d68447858b41b88b4be Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rjw@sisk.pl>
Date: Thu, 1 Mar 2012 00:06:33 +0100
Subject: PCI / PCIe: Introduce command line option to disable ARI

There are PCIe devices on the market that report ARI support but
then fail to initialize correctly when ARI is actually used.  This
leads to situations in which kernels 2.6.34 and newer fail to handle
systems where the previous kernels worked without any apparent
problems.  Unfortunately, it is currently unknown how many such
devices are there.

For this reason, introduce a new kernel command line option,
pci=noari, allowing users to disable PCIe ARI altogether if they
see problems with PCIe device initialization.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
---
 drivers/pci/pci.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'drivers/pci')

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b832f0fece9..81567441526 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -94,6 +94,9 @@ u8 pci_cache_line_size;
  */
 unsigned int pcibios_max_latency = 255;
 
+/* If set, the PCIe ARI capability will not be used. */
+static bool pcie_ari_disabled;
+
 /**
  * pci_bus_max_busnr - returns maximum PCI bus number of given bus' children
  * @bus: pointer to PCI bus structure to search
@@ -1955,7 +1958,7 @@ void pci_enable_ari(struct pci_dev *dev)
 	u16 flags, ctrl;
 	struct pci_dev *bridge;
 
-	if (!pci_is_pcie(dev) || dev->devfn)
+	if (pcie_ari_disabled || !pci_is_pcie(dev) || dev->devfn)
 		return;
 
 	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI);
@@ -3840,6 +3843,8 @@ static int __init pci_setup(char *str)
 				pci_realloc_get_opt("on");
 			} else if (!strcmp(str, "nodomains")) {
 				pci_no_domains();
+			} else if (!strncmp(str, "noari", 5)) {
+				pcie_ari_disabled = true;
 			} else if (!strncmp(str, "cbiosize=", 9)) {
 				pci_cardbus_io_size = memparse(str + 9, &str);
 			} else if (!strncmp(str, "cbmemsize=", 10)) {
-- 
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