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authorBenjamin Herrenschmidt <benh@kernel.crashing.org>2011-10-14 21:56:15 +0200
committerJesse Barnes <jbarnes@virtuousgeek.org>2011-10-27 21:45:44 +0200
commita1c473aa11e61bc871be16279c9bf976acf22504 (patch)
tree13f1c4565817bab8660e2e38f8fedc5344519788 /drivers/pci/pci.c
parentPCI: enable MPS "performance" setting to properly handle bridge MPS (diff)
downloadlinux-a1c473aa11e61bc871be16279c9bf976acf22504.tar.xz
linux-a1c473aa11e61bc871be16279c9bf976acf22504.zip
pci: Clamp pcie_set_readrq() when using "performance" settings
When configuring the PCIe settings for "performance", we allow parents to have a larger Max Payload Size than children and rely on children Max Read Request Size to not be larger than their own MPS to avoid having the host bridge generate responses they can't cope with. However, various drivers in Linux call pci_set_readrq() with arbitrary values, assuming this to be a simple performance tweak. This breaks under our "performance" configuration. Fix that by making sure the value programmed by pcie_set_readrq() is never larger than the configured MPS for that device. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Jon Mason <mason@myri.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Diffstat (limited to 'drivers/pci/pci.c')
-rw-r--r--drivers/pci/pci.c18
1 files changed, 16 insertions, 2 deletions
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7cd417e94058..6f45a73c6e9f 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3202,8 +3202,6 @@ int pcie_set_readrq(struct pci_dev *dev, int rq)
if (rq < 128 || rq > 4096 || !is_power_of_2(rq))
goto out;
- v = (ffs(rq) - 8) << 12;
-
cap = pci_pcie_cap(dev);
if (!cap)
goto out;
@@ -3211,6 +3209,22 @@ int pcie_set_readrq(struct pci_dev *dev, int rq)
err = pci_read_config_word(dev, cap + PCI_EXP_DEVCTL, &ctl);
if (err)
goto out;
+ /*
+ * If using the "performance" PCIe config, we clamp the
+ * read rq size to the max packet size to prevent the
+ * host bridge generating requests larger than we can
+ * cope with
+ */
+ if (pcie_bus_config == PCIE_BUS_PERFORMANCE) {
+ int mps = pcie_get_mps(dev);
+
+ if (mps < 0)
+ return mps;
+ if (mps < rq)
+ rq = mps;
+ }
+
+ v = (ffs(rq) - 8) << 12;
if ((ctl & PCI_EXP_DEVCTL_READRQ) != v) {
ctl &= ~PCI_EXP_DEVCTL_READRQ;