build failure from drm/ttm commit now in mainline (was: linux-next: build failure after merge of the drm tree)

[Michael Ellerman]

Thorsten Leemhuis <regressions at leemhuis.info> writes:
> Lo!
>
> Sometimes the regression tracker runs into regressions himself... :-D
>
> On 11.04.23 08:47, Stephen Rothwell wrote:
>> 
>> After merging the drm tree, today's linux-next build (powerpc
>> allyesconfig) failed like this:
>> 
>> drivers/gpu/drm/ttm/ttm_pool.c:73:29: error: variably modified 'global_write_combined' at file scope
>>    73 | static struct ttm_pool_type global_write_combined[TTM_DIM_ORDER];
>>       |                             ^~~~~~~~~~~~~~~~~~~~~
>> drivers/gpu/drm/ttm/ttm_pool.c:74:29: error: variably modified 'global_uncached' at file scope
>>    74 | static struct ttm_pool_type global_uncached[TTM_DIM_ORDER];
>>       |                             ^~~~~~~~~~~~~~~
>> drivers/gpu/drm/ttm/ttm_pool.c:76:29: error: variably modified 'global_dma32_write_combined' at file scope
>>    76 | static struct ttm_pool_type global_dma32_write_combined[TTM_DIM_ORDER];
>>       |                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/gpu/drm/ttm/ttm_pool.c:77:29: error: variably modified 'global_dma32_uncached' at file scope
>>    77 | static struct ttm_pool_type global_dma32_uncached[TTM_DIM_ORDER];
>>       |                             ^~~~~~~~~~~~~~~~~~~~~
>> 
>> Caused by commit
>> 
>>   322458c2bb1a ("drm/ttm: Reduce the number of used allocation orders for TTM pages")
>> 
>> PMD_SHIFT is not necessarily a constant on ppc (see
>> arch/powerpc/include/asm/book3s/64/pgtable.h).
>> 
>> I have reverted that commit for today.
>
> Did anyone look into this?

Christian sent a revert:
  56e51681246e ("drm/ttm: revert "Reduce the number of used allocation orders for TTM pages"")

Which has been in linux-next since the 21st. But I guess it missed being
in the initial DRM pull request.

See also other thread:
  https://lore.kernel.org/all/ZEljCgVFnDl%2FC+l3@debian/

Where Christian says the revert is "on the way" to Linus.

cheers