[PATCH v1] PCI: keystone: add a pci quirk to limit mrrs

From: Murali Karicheri
Date: Wed Aug 06 2014 - 13:04:10 EST


Keystone PCI controller has a limitation that memory read request
size must not exceed 256 bytes. This is a hardware limitation and
add a quirk to force this limit on all downstream devices by
updating mrrs.

Signed-off-by: Murali Karicheri <m-karicheri2@xxxxxx>
---
v1 - updated based on comments pr_info to dev_info
This applies on top of the Keystone PCI controller patch series
at http://thread.gmane.org/gmane.linux.kernel.pci/33523
drivers/pci/host/pci-keystone.c | 40 +++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)

diff --git a/drivers/pci/host/pci-keystone.c b/drivers/pci/host/pci-keystone.c
index c1cfaef..50d6995 100644
--- a/drivers/pci/host/pci-keystone.c
+++ b/drivers/pci/host/pci-keystone.c
@@ -42,8 +42,48 @@
/* DEV_STAT_CTRL */
#define PCIE_CAP_BASE 0x70

+/* PCIE controller device IDs */
+#define PCIE_RC_K2HK 0xb008
+#define PCIE_RC_K2E 0xb009
+#define PCIE_RC_K2L 0xb00a
+
#define to_keystone_pcie(x) container_of(x, struct keystone_pcie, pp)

+static void quirk_limit_mrrs(struct pci_dev *dev)
+{
+ struct pci_bus *bus = dev->bus;
+ struct pci_dev *bridge = bus->self;
+
+ if (pci_is_root_bus(bus))
+ return;
+
+ /* look for the host bridge */
+ while (!pci_is_root_bus(bus)) {
+ bridge = bus->self;
+ bus = bus->parent;
+ }
+
+ if (bridge) {
+ u16 id;
+
+ /*
+ * Keystone PCI controller has a h/w limitation of
+ * 256 bytes maximum read request size. It can't handle
+ * anything higher than this. So force this limit on
+ * all downstream devices
+ */
+ pci_read_config_word(bridge, PCI_DEVICE_ID, &id);
+ if ((id == PCIE_RC_K2HK) || (id == PCIE_RC_K2E) ||
+ (id == PCIE_RC_K2L)) {
+ if (pcie_get_readrq(dev) > 256) {
+ dev_info(&dev->dev, "limiting mrrs to 256\n");
+ pcie_set_readrq(dev, 256);
+ }
+ }
+ }
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_ANY_ID, PCI_ANY_ID, quirk_limit_mrrs);
+
static int ks_pcie_establish_link(struct keystone_pcie *ks_pcie)
{
struct pcie_port *pp = &ks_pcie->pp;
--
1.7.9.5

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