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

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On 4/22/2024 5:22 AM, Dmitry Baryshkov wrote:
On Fri, Apr 19, 2024 at 07:37:44PM -0700, Abhinav Kumar wrote:

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

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
    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,
@@ -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.

But populate function does the check. It seems like an overkill to add
another function. Also I still don't see the point. It was fine to call
this function from .prepare_fb, but it's not fine to call it from

As we discussed during the meeting, discarding rejected state is fine and is a commonly used practice, hence this is okay. I was only trying to avoid that.

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?

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