Yijing,
Seems you want to workaround platform bug in generic PCIe hotplug
code, while not specific to some platforms or devices, that is not
safe/fair to other vendor's platform.
and the updating to MPS of device is out of PCIe specification.
So the best way is to fix within platform, at least, any platform
specific way in Linux code.
Thanks,
Ethan
On Tue, Jul 29, 2014 at 4:17 PM, Yijing Wang <wangyijing@xxxxxxxxxx> wrote:
> Currently we don't update device's mps value when doing
> pci device hot-add. The hot-added device's mps will be set
> to default value (128B). But the upstream port device's mps
> may be larger than 128B which was set by firmware during
> system bootup. In this case the new added device may not
> work normally. This issue was found in huawei 5885 server
> and Dell R620 server. And if we run the platform with windows,
> this problem is gone. This patch try to update the hot added
> device mps equal to its parent mps, if device mpss < parent mps,
> print warning.
>
> References: https://bugzilla.kernel.org/show_bug.cgi?id=60671
> Reported-by: Keith Busch <keith.busch@xxxxxxxxx>
> Reported-by: Jordan_Hargrave@xxxxxxxx
> Reported-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> Cc: Jon Mason <jdmason@xxxxxxxx>
> ---
> drivers/pci/probe.c | 39 +++++++++++++++++++++++++++++++++++++++
> 1 files changed, 39 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index e3cf8a2..583ca52 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1613,6 +1613,44 @@ static void pcie_write_mrrs(struct pci_dev *dev)
> dev_err(&dev->dev, "MRRS was unable to be configured with a safe value. If problems are experienced, try running with pci=pcie_bus_safe\n");
> }
>
> +/**
> + * pcie_bus_update_set - update device mps when device doing hot-add
> + * @dev: PCI device to set
> + *
> + * After device hot add, mps will be set to default(128B), But the
> + * upstream port device's mps may be larger than 128B which was set
> + * by firmware during system bootup. Then we should update the device
> + * mps to equal to its parent mps, Or the device can not work normally.
> + */
> +static void pcie_bus_update_set(struct pci_dev *dev)
> +{
> + int mps, p_mps, mpss;
> + struct pci_dev *parent;
> +
> + if (!pci_is_pcie(dev) || !dev->bus->self
> + || !dev->bus->self->is_hotplug_bridge)
> + return;
> +
> + parent = dev->bus->self;
> + mps = pcie_get_mps(dev);
> + p_mps = pcie_get_mps(parent);
> +
> + if (mps >= p_mps)
> + return;
> +
> + mpss = 128 << dev->pcie_mpss;
> + if (mpss < p_mps) {
> + dev_warn(&dev->dev, "MPSS %d smaller than upstream MPS %d\n"
> + "If necessary, use \"pci=pcie_bus_safe\" boot parameter to avoid this problem\n",
> + mpss, p_mps);
> + return;
> + }
> +
> + pcie_write_mps(dev, p_mps);
> + dev_info(&dev->dev, "Max Payload Size set to %4d/%4d (was %4d)\n",
> + pcie_get_mps(dev), 128 << dev->pcie_mpss, mps);
> +}
> +
> static void pcie_bus_detect_mps(struct pci_dev *dev)
> {
> struct pci_dev *bridge = dev->bus->self;
> @@ -1637,6 +1675,7 @@ static int pcie_bus_configure_set(struct pci_dev *dev, void *data)
> return 0;
>
> if (pcie_bus_config == PCIE_BUS_TUNE_OFF) {
> + pcie_bus_update_set(dev);
> pcie_bus_detect_mps(dev);
> return 0;
> }
> --
> 1.7.1
>
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