linux-kernel - Re: [PATCH v6 05/11] drm/msm/a6xx: Implement preemption for a7xx targets

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Message-ID: <a035fb73-e2b8-4928-b136-b3b99996bc84@gmail.com>
Date: Fri, 27 Sep 2024 22:15:22 +0200
From: Antonino Maniscalco <antomani103@...il.com>
To: Rob Clark <robdclark@...il.com>
Cc: Sean Paul <sean@...rly.run>, Konrad Dybcio <konrad.dybcio@...aro.org>,
 Abhinav Kumar <quic_abhinavk@...cinc.com>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Jonathan Corbet <corbet@....net>, linux-arm-msm@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 Akhil P Oommen <quic_akhilpo@...cinc.com>,
 Neil Armstrong <neil.armstrong@...aro.org>,
 Sharat Masetty <smasetty@...eaurora.org>
Subject: Re: [PATCH v6 05/11] drm/msm/a6xx: Implement preemption for a7xx
 targets

On 9/27/24 6:29 PM, Rob Clark wrote:
> On Thu, Sep 26, 2024 at 2:17 PM Antonino Maniscalco
> <antomani103@...il.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.
>>
>> Reviewed-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
>> Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8650-QRD
>> Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8550-QRD
>> Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8450-HDK
>> Signed-off-by: Sharat Masetty <smasetty@...eaurora.org>
>> Signed-off-by: Antonino Maniscalco <antomani103@...il.com>
>> ---
>>   drivers/gpu/drm/msm/Makefile              |   1 +
>>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c     | 283 +++++++++++++++++++++-
>>   drivers/gpu/drm/msm/adreno/a6xx_gpu.h     | 168 +++++++++++++
>>   drivers/gpu/drm/msm/adreno/a6xx_preempt.c | 377 ++++++++++++++++++++++++++++++
>>   drivers/gpu/drm/msm/msm_ringbuffer.h      |   7 +
>>   5 files changed, 825 insertions(+), 11 deletions(-)
>>
> 
> [snip]
> 
>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> index 6e065500b64d6d95599d89c33e6703c92f210047..355a3e210335d60a5bed0ee287912271c353402a 100644
>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> 
> [snip]
> 
>> @@ -784,6 +1015,16 @@ 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);
> 
> Couldn't this also be MSM_BO_GPU_READONLY?  And same for the
> preempt_postamble_ptr, I assume?

So for pwrup_reglist_ptr, it contains the cpu_gpu_lock struct that needs 
to be written by the gpu. The list itself is part of that struct.

> 
> Also, it looks like we are only writing the smmu_info from the
> kernel.. is there any way that could be split out into a RO buffer?

For preempt_postamble_ptr, and smmu_info I think it should be possible 
so I'll work on that.

> 
> BR,
> -R
> 
>> +
>> +       if (IS_ERR(a6xx_gpu->pwrup_reglist_ptr))
>> +               return PTR_ERR(a6xx_gpu->pwrup_reglist_ptr);
>> +
>> +       msm_gem_object_set_name(a6xx_gpu->pwrup_reglist_bo, "pwrup_reglist");
>> +
>>          return 0;
>>   }
>>


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