[PATCH] drm/radeon: insist on 32-bit DMA for Cedar

[Christian König]

Am 22.02.2018 um 03:05 schrieb Alex Deucher:
> On Wed, Feb 21, 2018 at 6:41 PM, Ben Crocker <bcrocker at redhat.com> wrote:
>> In radeon_device_init, set the need_dma32 flag for Cedar chips
>> (e.g. FirePro 2270).  This fixes, or at least works around, a bug
>> on PowerPC exposed by last year's commits
>>
>> 8e3f1b1d8255105f31556aacf8aeb6071b00d469 (Russell Currey)
>>
>> and
>>
>> 253fd51e2f533552ae35a0c661705da6c4842c1b (Alistair Popple)
>>
>> which enabled the 64-bit DMA iommu bypass.
>>
>> This caused the device to freeze, in some cases unrecoverably, and is
>> the subject of several bug reports internal to Red Hat.
> Can we make this ppc only?  40 bit DMA works fine on x86.

Yeah and at least when the dma_coherent allocator path is used it should 
work fine on PPC as well.

So that is not really a driver bug, but a platform bug and we should 
think about reverting or at least disabling those two patches instead.

Christian.

>
> Alex
>
>> Signed-off-by: Ben Crocker <bcrocker at redhat.com>
>> ---
>>   drivers/gpu/drm/radeon/radeon_device.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
>> index ffc10cadcf34..02538903830d 100644
>> --- a/drivers/gpu/drm/radeon/radeon_device.c
>> +++ b/drivers/gpu/drm/radeon/radeon_device.c
>> @@ -1395,7 +1395,10 @@ int radeon_device_init(struct radeon_device *rdev,
>>          if (rdev->flags & RADEON_IS_AGP)
>>                  rdev->need_dma32 = true;
>>          if ((rdev->flags & RADEON_IS_PCI) &&
>> -           (rdev->family <= CHIP_RS740))
>> +           (rdev->family <= CHIP_RS740 || rdev->family == CHIP_CEDAR))
>> +               rdev->need_dma32 = true;
>> +       if ((rdev->flags & RADEON_IS_PCIE) &&
>> +           (rdev->family == CHIP_CEDAR))
>>                  rdev->need_dma32 = true;
>>
>>          dma_bits = rdev->need_dma32 ? 32 : 40;
>> --
>> 2.13.6
>>
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>> dri-devel at lists.freedesktop.org
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