>>
>> diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
>> index 305a657..3291f62 100644
>> --- a/drivers/gpu/drm/radeon/evergreen.c
>> +++ b/drivers/gpu/drm/radeon/evergreen.c
>> @@ -3855,8 +3855,7 @@ void evergreen_fini(struct radeon_device *rdev)
>>
>> void evergreen_pcie_gen2_enable(struct radeon_device *rdev)
>> {
>> - u32 link_width_cntl, speed_cntl, mask;
>> - int ret;
>> + u32 link_width_cntl, speed_cntl;
>>
>> if (radeon_pcie_gen2 == 0)
>> return;
>> @@ -3871,11 +3870,7 @@ void evergreen_pcie_gen2_enable(struct radeon_device *rdev)
>> if (ASIC_IS_X2(rdev))
>> return;
>>
>> - ret = drm_pcie_get_speed_cap_mask(rdev->ddev, &mask);
>> - if (ret != 0)
>> - return;
>> -
>> - if (!(mask & DRM_PCIE_SPEED_50))
>> + if (rdev->pdev->bus->max_bus_speed < PCIE_SPEED_5_0GT)
>
> For devices on a root bus, we previously dereferenced a NULL pointer
> in drm_pcie_get_speed_cap_mask() because pdev->bus->self is NULL on a
> root bus. (I think this is the original problem you tripped over,
> Lucas.)
>
> These patches fix that problem. On pseries, where the device *is* on
> a root bus, your patches set max_bus_speed so this will work as
> expected. On most other systems, max_bus_speed for root buses will be
> PCI_SPEED_UNKNOWN (set in pci_alloc_bus() and never updated because
> most arches don't have code like the pseries code you're adding).
>
> PCI_SPEED_UNKNOWN = 0xff, so if we see another machine with a GPU on
> the root bus, we'll attempt to enable Gen2 on the device even though
> we have no idea what the bus will support.
>
> That's why I originally suggested skipping the Gen2 stuff if
> "max_bus_speed == PCI_SPEED_UNKNOWN". I was just being conservative,
> thinking that it's better to have a functional but slow GPU rather
> than the unknown (to me) effects of enabling Gen2 on a link that might
> not support it. But I'm fine with this being either way.
>
> It would be nice if we could get rid of drm_pcie_get_speed_cap_mask()
> altogether. It is exported, but I have no idea of anybody else uses
> it. Maybe it could at least be marked __deprecated now?
>
> I don't know who should take these patches. They don't touch
> drivers/pci, but I'd be happy to push them, given the appropriate ACKs
> from DRM and powerpc folks.
>
Acked-by: Dave Airlie <airlied@xxxxxxxxxx>
I'm happy to see these go via pci tree to avoid interdependent trees.
Dave.
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