On Thu, Oct 10, 2019 at 02:17:44PM -0400, Sean Paul wrote:
> From: Sean Paul <seanp...@chromium.org>
>
> As Daniel mentions in his email [1], non-blocking commits don't hold the
> modeset locks, so we can safely access state as long as these functions
> are in the commit path. So remove the WARN_ON in dpu_kms_encoder_enable.
>
> In dpu_crtc_get_intf_mode, things are a bit more complicated. So keep
> the WARN_ON, but add a comment explaining the situation and hope someone
> comes along and fixes the issue.
>
> [1]- https://lists.freedesktop.org/archives/dri-devel/2019-October/239441.html
>
> Link to v1:
> https://patchwork.freedesktop.org/patch/msgid/20191010151351.126735-1-s...@poorly.run
>
> Changes in v2:
> - Restored the WARN_ON in get_intf_mode and added a clarifying comment
> (Daniel)
>
> Fixes: 1dfdb0e107db ("drm/msm: dpu: Add modeset lock checks where applicable")
> Cc: Jeykumar Sankaran <jsa...@codeaurora.org>
> Cc: Rob Clark <robdcl...@chromium.org>
> Suggested-by: Daniel Vetter <dan...@ffwll.ch>
> Partially-Reviewed-by: Daniel Vetter <daniel.vet...@ffwll.ch>
Applied to msm-next with danvet's full irc r-b, thanks for the report and
review!
Sean
> Signed-off-by: Sean Paul <seanp...@chromium.org>
> ---
> drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 9 +++++++++
> drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 1 -
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> index 0b9dc042d2e22..f197dce545761 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> @@ -271,6 +271,15 @@ enum dpu_intf_mode dpu_crtc_get_intf_mode(struct
> drm_crtc *crtc)
> return INTF_MODE_NONE;
> }
>
> + /*
> + * TODO: This function is called from dpu debugfs and as part of atomic
> + * check. When called from debugfs, the crtc->mutex must be held to
> + * read crtc->state. However reading crtc->state from atomic check isn't
> + * allowed (unless you have a good reason, a big comment, and a deep
> + * understanding of how the atomic/modeset locks work (<- and this is
> + * probably not possible)). So we'll keep the WARN_ON here for now, but
> + * really we need to figure out a better way to track our operating mode
> + */
> WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
>
> /* TODO: Returns the first INTF_MODE, could there be multiple values? */
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index b1645ad83a1e1..6c92f0fbeac98 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -316,7 +316,6 @@ void dpu_kms_encoder_enable(struct drm_encoder *encoder)
> if (funcs && funcs->commit)
> funcs->commit(encoder);
>
> - WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
> drm_for_each_crtc(crtc, dev) {
> if (!(crtc->state->encoder_mask & drm_encoder_mask(encoder)))
> continue;
> --
> Sean Paul, Software Engineer, Google / Chromium OS
>
--
Sean Paul, Software Engineer, Google / Chromium OS
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