On 12/3/2024 5:53 AM, Dmitry Baryshkov wrote:
On Mon, Dec 02, 2024 at 04:39:01PM -0800, Abhinav Kumar wrote:
The checks in msm_dp_display_prepare() for making sure that we are in
ST_DISPLAY_OFF OR ST_MAINLINK_READY seem redundant.
DRM fwk shall not issue any commits if state is not ST_MAINLINK_READY as
msm_dp's atomic_check callback returns a failure if state is not ST_MAINLINK_READY.
Can the state change between atomic_check() and atomic_commit()?
Good question.
I cannot deny that such a possibility does exist.
From what I can see in the state machine today, the only possibility I
can think of here is if a user very quickly removes the cable as soon as
they connect the cable like so fast that the connect was not yet
processed before disconnect.
Similarly, if an irq_hpd fires after atomic_check but before
atomic_enable(), and moreover if we hit the sink_count == 0 case in
msm_dp_display_handle_port_status_changed() during this irq_hpd,
In both these cases, then we will transition to ST_DISCONNECT_PENDING state.
Without this change, we would have bailed out in the
ST_DISCONNECT_PENDING case.
But other than this, I cannot atleast think of a case where a different
state transition can happen between atomic_check() and atomic_commit()
because for other transitions, I think we should be still okay.
But this is purely based on theoretical observation and hypothesis.
Is it better to add a check to bail out in the DISCONNECT_PENDING case?
OR document this as "To-do: Need to bail out if DISCONNECT_PENDING"
because even if I add this check, I dont know if can make sure this can
be validated as the check could never hit.
For the ST_DISPLAY_OFF check, its mainly to guard against a scenario that
there is an atomic_enable() without a prior atomic_disable() which once again
should not really happen.
To simplify the code, get rid of these checks.
Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
---
drivers/gpu/drm/msm/dp/dp_display.c | 6 ------
1 file changed, 6 deletions(-)
diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 992184cc17e4..614fff09e5f2 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -1513,12 +1513,6 @@ void msm_dp_bridge_atomic_enable(struct drm_bridge *drm_bridge,
return;
}
- state = msm_dp_display->hpd_state;
- if (state != ST_DISPLAY_OFF && state != ST_MAINLINK_READY) {
- mutex_unlock(&msm_dp_display->event_mutex);
- return;
- }
-
rc = msm_dp_display_set_mode(dp, &msm_dp_display->msm_dp_mode);
if (rc) {
DRM_ERROR("Failed to perform a mode set, rc=%d\n", rc);
--
2.34.1
