On Fri, Aug 08, 2014 at 03:45:32PM -0400, Murali Karicheri wrote:
> 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 <[email protected]>
> ---
> -v2: made the quirk happens after tuning
> -v1: changed printk to indicate PCI bdf
> 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..a132622 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
A Root Complex doesn't appear in config space as a PCI device, so I think
these are actually Root Port devices, aren't they?
I suppose the spec would allow Root Complex Integrated Endpoints, on which
MRRS could also be set, but I think your quirk ignores them because they
would appear on the root bus. Is ignoring them OK, or would you want to
set MRRS for those as well?
> +
> #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);
I think you should check the Vendor ID here as well. Otherwise, there's a
possibility of applying this quirk to devices under a bridge with the same
Device ID but different Vendor ID.
And I think you should be able to use the bridge->vendor and bridge->device
fields instead of reading them from config space. Actually, this might be
a good place to use pci_match_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_ENABLE(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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