Re: [PATCH] PCI: update device mps when doing pci hotplug

[Yijing Wang <wangyijing@huawei.com>]

>> Yes, that issue is BIOS bug, the mps setting is wrong after system boot up.
>> But that issue is not same as this one, Keith and Jordan found the issue
>> after hot-plug. And my patch only modify the hotplug slot connected device.
>>
>> In my idea, make the device work is important, because these platforms with windows
>> can run happy, why linux leave this issue to BIOS.
> 
>    That is a reason to make it works with Linux, but does your
> platform have _HPX from ACPI for those hot-added back devices ?  if it
> has, maybe windows could apply _HPX to configure those devices and
> work well.
> 

I checked DSDT table exported from my server, but no "_HPX" found.
Further more, kernel use pciehp first to support pcie hotplug device. And in pciehp,
driver won't touch ACPI methods like "_HPX".

Thanks!
Yijing.

>>
>>>
>>>> Reported-by: Keith Busch <keith.busch@intel.com>
>>>> Reported-by: Jordan_Hargrave@Dell.com
>>>> Reported-by: Yijing Wang <wangyijing@huawei.com>
>>>> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
>>>> Cc: Jon Mason <jdmason@kudzu.us>
>>>> ---
>>>>  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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>>>
>>> .
>>>
>>
>>
>> --
>> Thanks!
>> Yijing
>>
> 
> .
> 


-- 
Thanks!
Yijing