Re: [PATCH v2 4/9] drm/msm/A6xx: Implement preemption for A7XX targets

[Antonino Maniscalco <antomani103@gmail.com>]

On 8/30/24 10:25 PM, Rob Clark wrote:
> On Fri, Aug 30, 2024 at 8:33 AM Antonino Maniscalco
> <antomani103@gmail.com> wrote:
>>
>> This patch implements preemption feature for A6xx targets, this allows
>> the GPU to switch to a higher priority ringbuffer if one is ready. A6XX
>> hardware as such supports multiple levels of preemption granularities,
>> ranging from coarse grained(ringbuffer level) to a more fine grained
>> such as draw-call level or a bin boundary level preemption. This patch
>> enables the basic preemption level, with more fine grained preemption
>> support to follow.
>>
>> Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>
>> Signed-off-by: Antonino Maniscalco <antomani103@gmail.com>
>> Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8650-QRD
>> ---
>>   drivers/gpu/drm/msm/Makefile              |   1 +
>>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c     | 323 +++++++++++++++++++++-
>>   drivers/gpu/drm/msm/adreno/a6xx_gpu.h     | 168 ++++++++++++
>>   drivers/gpu/drm/msm/adreno/a6xx_preempt.c | 431 ++++++++++++++++++++++++++++++
>>   drivers/gpu/drm/msm/msm_ringbuffer.h      |   7 +
>>   5 files changed, 921 insertions(+), 9 deletions(-)
>>
> 
> [snip]
> 
>> @@ -784,6 +1062,16 @@ static int a6xx_ucode_load(struct msm_gpu *gpu)
>>                  msm_gem_object_set_name(a6xx_gpu->shadow_bo, "shadow");
>>          }
>>
>> +       a6xx_gpu->pwrup_reglist_ptr = msm_gem_kernel_new(gpu->dev, PAGE_SIZE,
>> +                                                        MSM_BO_WC  | MSM_BO_MAP_PRIV,
>> +                                                        gpu->aspace, &a6xx_gpu->pwrup_reglist_bo,
>> +                                                        &a6xx_gpu->pwrup_reglist_iova);
> 
> I guess this could also be MSM_BO_GPU_READONLY?
> 
> BR,
> -R

Besides containing the the actual reglist this buffer also contains the 
`cpu_gpu_lock` structure which is written by the SQE so adding the 
`MSM_BO_GPU_READONLY` flag would cause it to fault.

Best regards,
-- 
Antonino Maniscalco <antomani103@gmail.com>