Re: [PATCH v4] drm/msm/dpu1: don't choke on disabling the writeback connector

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On 12/9/2024 2:04 AM, Dmitry Baryshkov wrote:
During suspend/resume process all connectors are explicitly disabled and
then reenabled. However resume fails because of the connector_status check:

[dpu error]connector not connected 3
[drm:drm_mode_config_helper_resume [drm_kms_helper]] *ERROR* Failed to resume (-22)

It doesn't make sense to check for the Writeback connected status (and
other drivers don't perform such check), so drop the check.

It wasn't a problem before the commit 71174f362d67 ("drm/msm/dpu: move
writeback's atomic_check to dpu_writeback.c"), since encoder's
atomic_check() is called under a different conditions that the
connector's atomic_check() (e.g. it is not called if there is no
connected CRTC or if the corresponding connector is not a part of the
new state).

Fixes: 71174f362d67 ("drm/msm/dpu: move writeback's atomic_check to dpu_writeback.c")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Leonard Lausen <leonard@xxxxxxxxx>
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/57
Tested-by: Leonard Lausen <leonard@xxxxxxxxx> # on sc7180 lazor
Reported-by: György Kurucz <me@xxxxxxxxxxxx>
Link: https://lore.kernel.org/all/b70a4d1d-f98f-4169-942c-cb9006a42b40@xxxxxxxxxxxx/
Reported-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
Link: https://lore.kernel.org/all/ZzyYI8KkWK36FfXf@xxxxxxxxxxxxxxxxxxxx/
Tested-by: György Kurucz <me@xxxxxxxxxxxx>
Reviewed-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
Tested-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
Leonard Lausen reported an issue with suspend/resume of the sc7180
devices. Fix the WB atomic check, which caused the issue.
---
Changes in v4:
- Epanded commit message (Johan)
- Link to v3: https://lore.kernel.org/r/20241208-dpu-fix-wb-v3-1-a1de69ce4a1b@xxxxxxxxxx

Changes in v3:
- Rebased on top of msm-fixes
- Link to v2: https://lore.kernel.org/r/20240802-dpu-fix-wb-v2-0-7eac9eb8e895@xxxxxxxxxx

Changes in v2:
- Reworked the writeback to just drop the connector->status check.
- Expanded commit message for the debugging patch.
- Link to v1: https://lore.kernel.org/r/20240709-dpu-fix-wb-v1-0-448348bfd4cb@xxxxxxxxxx
---
  drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c | 3 ---
  1 file changed, 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c
index 16f144cbc0c986ee266412223d9e605b01f9fb8c..8ff496082902b1ee713e806140f39b4730ed256a 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c
@@ -42,9 +42,6 @@ static int dpu_wb_conn_atomic_check(struct drm_connector *connector,
  	if (!conn_state || !conn_state->connector) {
  		DPU_ERROR("invalid connector state\n");
  		return -EINVAL;
-	} else if (conn_state->connector->status != connector_status_connected) {
-		DPU_ERROR("connector not connected %d\n", conn_state->connector->status);
-		return -EINVAL;
  	}

Can you please explain me about why the status was not already connected?

In all the places I checked (unless I missed something), if the detect() callback is not registered, the connector is assumed connected like below:

404 	if (funcs->detect_ctx)
405 		ret = funcs->detect_ctx(connector, ctx, force);
406 	else if (connector->funcs->detect)
407 		ret = connector->funcs->detect(connector, force);
408 	else
409 		ret = connector_status_connected;

We do not register .detect for WB as WB connector should be always connected.

What scenario or use-case is making the connector status to something other than connected?

The places which mark the connector as unknown seem to be covered by warnings in drm_probe_helper.c but the bug report doesnt seem to be hitting those.

I am wondering if there is some case in fwk resetting this to unknown silently (which is incorrect) and perhaps other drivers dont hit this as there is a .detect registered which always returns connected and MSM should follow that.

111 static enum drm_connector_status
112 komeda_wb_connector_detect(struct drm_connector *connector, bool force)
113 {
114 	return connector_status_connected;
115 }
116
crtc = conn_state->crtc;

---
base-commit: 86313a9cd152330c634b25d826a281c6a002eb77
change-id: 20240709-dpu-fix-wb-6cd57e3eb182

Best regards,



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