[PATCH 4/9] drm/msm/dpu: move dpu_format_populate_plane_sizes to atomic_check

[Abhinav Kumar]

On 4/19/2024 6:34 PM, Dmitry Baryshkov wrote:
> On Fri, Apr 19, 2024 at 05:14:01PM -0700, Abhinav Kumar wrote:
>>
>>
>> On 3/19/2024 6:22 AM, Dmitry Baryshkov wrote:
>>> Move a call to dpu_format_populate_plane_sizes() to the atomic_check
>>> step, so that any issues with the FB layout can be reported as early as
>>> possible.
>>>
>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
>>> ---
>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 12 ++++++------
>>>    1 file changed, 6 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
>>> index d9631fe90228..a9de1fbd0df3 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
>>> @@ -673,12 +673,6 @@ static int dpu_plane_prepare_fb(struct drm_plane *plane,
>>>    		}
>>>    	}
>>> -	ret = dpu_format_populate_plane_sizes(new_state->fb, &pstate->layout);
>>> -	if (ret) {
>>> -		DPU_ERROR_PLANE(pdpu, "failed to get format plane sizes, %d\n", ret);
>>> -		return ret;
>>> -	}
>>> -
>>>    	/* validate framebuffer layout before commit */
>>>    	ret = dpu_format_populate_addrs(pstate->aspace,
>>>    					new_state->fb,
>>> @@ -864,6 +858,12 @@ static int dpu_plane_atomic_check(struct drm_plane *plane,
>>>    		return -E2BIG;
>>>    	}
>>> +	ret = dpu_format_populate_plane_sizes(new_plane_state->fb, &pstate->layout);
>>> +	if (ret) {
>>> +		DPU_ERROR_PLANE(pdpu, "failed to get format plane sizes, %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +
>>
>> I think we need another function to do the check. It seems incorrect to
>> populate the layout to the plane state knowing it can potentially fail.
> 
> why? The state is interim object, which is subject to checks. In other
> parts of the atomic_check we also fill parts of the state, perform
> checks and then destroy it if the check fails.
> 

Yes, the same thing you wrote.

I felt we can perform the validation and reject it before populating it 
in the state as it seems thats doable here rather than populating it 
without knowing whether it can be discarded.

> Maybe I'm missing your point here. Could you please explain what is the
> problem from your point of view?
> 
>>
>> Can we move the validation part of dpu_format_populate_plane_sizes() out to
>> another helper dpu_format_validate_plane_sizes() and use that?
>>
>> And then make the remaining dpu_format_populate_plane_sizes() just a void
>> API to fill the layout?
>