On 3/18/19 1:19 PM, Mario Kleiner wrote:
> During VRR mode we can not allow vblank irq dis-/enable
> transitions, as an enable after a disable can happen at
> an arbitrary time during the video refresh cycle, e.g.,
> with a high likelyhood inside vblank front-porch. An
> enable during front-porch would cause vblank timestamp
> updates/calculations which are completely bogus, given
> the code can't know when the vblank will end as long
> as we are in front-porch with no page flip completed.
>
> Hold a permanent vblank reference on the crtc while
> in active VRR mode to prevent a vblank disable, and
> drop the reference again when switching back to fixed
> refresh rate non-VRR mode.
>
> Signed-off-by: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
> ---
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 35 +++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index a718ac2..c1c3815 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -251,6 +251,12 @@ get_crtc_by_otg_inst(struct amdgpu_device *adev,
> return NULL;
> }
>
> +static inline bool amdgpu_dm_vrr_active(struct dm_crtc_state *dm_state)
> +{
> + return dm_state->freesync_config.state == VRR_STATE_ACTIVE_VARIABLE ||
> + dm_state->freesync_config.state == VRR_STATE_ACTIVE_FIXED;
> +}
> +
> static void dm_pflip_high_irq(void *interrupt_params)
> {
> struct amdgpu_crtc *amdgpu_crtc;
> @@ -4716,6 +4722,32 @@ static void update_freesync_state_on_stream(
> (int)vrr_params.state);
> }
>
> +static void amdgpu_dm_handle_vrr_transition(struct dm_crtc_state *old_state,
> + struct dm_crtc_state *new_state)
> +{
> + bool old_vrr_active = amdgpu_dm_vrr_active(old_state);
> + bool new_vrr_active = amdgpu_dm_vrr_active(new_state);
> +
> + if (!old_vrr_active && new_vrr_active) {
> + /* Transition VRR inactive -> active:
> + * While VRR is active, we must not disable vblank irq, as a
> + * reenable after disable would compute bogus vblank/pflip
> + * timestamps if it likely happened inside display front-porch.
> + */
> + drm_crtc_vblank_get(new_state->base.crtc);
> + DRM_DEBUG_DRIVER("%s: crtc=%u VRR off->on: Get vblank ref\n",
> + __func__, new_state->base.crtc->base.id);
> + }
> + else if (old_vrr_active && !new_vrr_active) {
> + /* Transition VRR active -> inactive:
> + * Allow vblank irq disable again for fixed refresh rate.
> + */
> + drm_crtc_vblank_put(new_state->base.crtc);
> + DRM_DEBUG_DRIVER("%s: crtc=%u VRR on->off: Drop vblank ref\n",
> + __func__, new_state->base.crtc->base.id);
> + }
> +}
> +
> static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
> struct dc_state *dc_state,
> struct drm_device *dev,
> @@ -4757,6 +4789,9 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
> goto cleanup;
> }
>
> + /* Take care to hold extra vblank ref for a crtc in VRR mode */
> + amdgpu_dm_handle_vrr_transition(dm_old_crtc_state, acrtc_state);
I think this forgets to drop the extra reference in the case where the
stream is being disabled at the same time VRR is -
amdgpu_dm_commit_planes is only called when when the stream is non-NULL.
I think the logic will work if simply moved outside of the function into
the loop that calls this.
Nicholas Kazlauskas
> +
> /* update planes when needed */
> for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) {
> struct drm_crtc *crtc = new_plane_state->crtc;
>
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