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>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7dc523e082a28b47756784cd6cd7db95fc2a07e1..3d153e5723b4eaa5061bd07d6cce3b96054a2b3f 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2116,6 +2116,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                                off: Turn realloc off
                                on: Turn realloc on
                realloc         same as realloc=on
+               noari           do not use PCIe ARI.
 
        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
                        Management.

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b832f0fece97f8ca8d2a831c9414ccb41b6e16a1..815674415267d831a2618b1e1f977c080d34ac92 100644 (file)
--- 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)) {