Hardware 3D acceleration doesn't work anymore with the latest git kernel

[Tom St Denis]

On 27/11/17 07:02 AM, Michel Dänzer wrote:
> On 2017-11-27 12:50 PM, Christian König wrote:
>> Am 27.11.2017 um 12:02 schrieb Michel Dänzer:
>>> On 2017-11-24 05:09 PM, Michel Dänzer wrote:
>>>> On 2017-11-24 03:29 PM, Christian Zigotzky wrote:
>>>>> Hi All,
>>>>>
>>>>> I bisected today and the first bad commit is:
>>>>> a4dec819c8bba6365eb893a4ca88db4dd1210110 (drm/ttm: Add helper functions
>>>>> to populate/map in one call (v2)) [1]
>>>> It can't really be that commit, since it just adds functions but doesn't
>>>> hook them up anywhere. Presumably it's commit
>>>> f7871fd19389c5f64f625a4389675d0740f0dfe4 ("drm/radeon: use new TTM
>>>> populate/dma map helper functions") instead, which makes the radeon
>>>> driver rely on ttm_populate_and_map_pages, which is just a stub
>>>> returning -ENOMEM when neither CONFIG_SWIOTLB nor CONFIG_INTEL_IOMMU is
>>>> enabled.
>>>>
>>>> I can see two possible solutions:
>>>>
>>>> 1. Make ttm_populate_and_map_pages and ttm_unmap_and_unpopulate_pages
>>>>      work without SWIOTLB / INTEL_IOMMU as well.
>>>>
>>>> 2. Make the drivers work without ttm_populate_and_map_pages and
>>>>      ttm_unmap_and_unpopulate_pages again in that case.
>>>>
>>>>
>>>> Solution 1 would be preferable.
>>> Which solution do you want to go for?
>>
>> well, can somebody please explain to me why those patches actually
>> result in problems?
> 
> I thought I did above...
> 
> Commit f7871fd19389c5f64f625a4389675d0740f0dfe4 made the radeon driver
> rely on ttm_populate_and_map_pages, which is implemented as:
> 
> static inline int ttm_populate_and_map_pages(struct device *dev, struct ttm_dma_tt *tt)
> {
> 	return -ENOMEM;
> }
> 
> when neither CONFIG_SWIOTLB nor CONFIG_INTEL_IOMMU is enabled.
> Previously, the driver worked fine without either of those enabled.
> 
> 

I think the issue is why would you have both disabled and we did run 
into a kbuild error when they weren't guarded (I don't remember exactly 
what though I'd have to go grep for it).

TOm