[PATCH v3 6/8] drm/msm/dpu: add support for MDP_TOP blackhole

[Abhinav Kumar]

On 11/16/2022 12:19 AM, Dmitry Baryshkov wrote:
> On 16/11/2022 10:50, Abhinav Kumar wrote:
>>
>>
>> On 11/4/2022 6:03 AM, Dmitry Baryshkov wrote:
>>> On sm8450 a register block was removed from MDP TOP. Accessing it during
>>> snapshotting results in NoC errors / immediate reboot. Skip accessing
>>> these registers during snapshot.
>>>
>>> Tested-by: Vinod Koul <vkoul at kernel.org>
>>> Reviewed-by: Vinod Koul <vkoul at kernel.org>
>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
>>
>> I am confused with both the ordering and the split of this patch.
>>
>> You have defined DPU_MDP_PERIPH_0_REMOVED in the catalog header file 
>> in this patch but used it in the next.
>>
>> But you also have code in this patch which relies on setting of this bit.
>>
>> So if this patch is taken without the next, it will still crash.
> 
> It will not crash if this patch is taken without the next one. Without 
> the next patch the DPU driver will not match and bind against the 
> qcom,sm8450-dpu device.

Ah okay, I just now saw that you have the compatible change also in the 
next patch.

> 
> So, the ordering is quite logical from my point of view:
> - add support for all the features required for the device
> - add the device compat string & catalog entry
> 
>>
>> Rather, you should combine the define part of this patch to the next 
>> patch in the series 
>> https://patchwork.freedesktop.org/patch/510114/?series=108883&rev=3 , 
>> then move that one in front of this patch.
> 
> No. This way we'll have a state (after adding the next patch) when the 
> sm8450 support is enabled, but the top-hole is not handled, leading to a 
> crash.
> 

What if you split the compatible to a separate patch like what SM8350 did.

https://patchwork.freedesktop.org/patch/511659/?series=110924&rev=1

So, we have hw catalog changes ---> snapshot fix ---> add the compatible.

That will make both of us happy?

>>
>> So that its much more coherent that you defined 
>> DPU_MDP_PERIPH_0_REMOVED both in the catalog header and used it in the 
>> catalog.c file and the in the next change you used the caps to avoid 
>> touching that register.
> 
> I'd say it's rather strange way. When I see a define/feature addition, 
> I'd prefer to seethe implementation too.
> 
>> Regarding the TOP hole itself, I need one day to investigate this. I 
>> am waiting for permissions to the documentation.
>>
>> If i cannot get access by the time you have re-ordered this, I will 
>> ack this once the reorder is done within a day.
> 
> 
> For the reference: [1]
> 
> [1] 
> https://git.codelinaro.org/clo/la/platform/vendor/opensource/display-drivers/-/commit/f9ff8af5b640147f3651c23551c60f81f62874b1 
> 
> 
>>
>>> ---
>>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h |  1 +
>>>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c        | 11 +++++++++--
>>>   2 files changed, 10 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h 
>>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
>>> index 38aa38ab1568..4730f8268f2a 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
>>> @@ -92,6 +92,7 @@ enum {
>>>       DPU_MDP_UBWC_1_0,
>>>       DPU_MDP_UBWC_1_5,
>>>       DPU_MDP_AUDIO_SELECT,
>>> +    DPU_MDP_PERIPH_0_REMOVED,
>>>       DPU_MDP_MAX
>>>   };
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c 
>>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>>> index f3660cd14f4f..95d8765c1c53 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>>> @@ -927,8 +927,15 @@ static void dpu_kms_mdp_snapshot(struct 
>>> msm_disp_state *disp_state, struct msm_k
>>>           msm_disp_snapshot_add_block(disp_state, cat->wb[i].len,
>>>                   dpu_kms->mmio + cat->wb[i].base, "wb_%d", i);
>>> -    msm_disp_snapshot_add_block(disp_state, cat->mdp[0].len,
>>> -            dpu_kms->mmio + cat->mdp[0].base, "top");
>>> +    if (dpu_kms->hw_mdp->caps->features & 
>>> BIT(DPU_MDP_PERIPH_0_REMOVED)) {
>>> +        msm_disp_snapshot_add_block(disp_state, 0x380,
>>> +                dpu_kms->mmio + cat->mdp[0].base, "top");
>>> +        msm_disp_snapshot_add_block(disp_state, cat->mdp[0].len - 
>>> 0x3a8,
>>> +                dpu_kms->mmio + cat->mdp[0].base + 0x3a8, "top_2");
>>> +    } else {
>>> +        msm_disp_snapshot_add_block(disp_state, cat->mdp[0].len,
>>> +                dpu_kms->mmio + cat->mdp[0].base, "top");
>>> +    }
>>>       pm_runtime_put_sync(&dpu_kms->pdev->dev);
>>>   }
>