Hi Laurent,
I've just seen Maxime's latest series "[PATCH 0/4] drm/sun4i: Fix a register
access bug" and it relates directly to a comment I had in this patch:
On 12/07/17 17:35, Kieran Bingham wrote:
> Hi Laurent,
>
> On 28/06/17 19:50, Laurent Pinchart wrote:
>> Commit 52055bafa1ff ("drm: rcar-du: Move plane commit code from CRTC
>> start to CRTC resume") changed the order of the plane commit and CRTC
>> enable operations to accommodate the runtime PM requirements. However,
>> this introduced corruption in the first displayed frame, as the CRTC is
>> now enabled without any plane configured. On Gen2 hardware the first
>> frame will be black and likely unnoticed, but on Gen3 hardware we end up
>> starting the display before the VSP compositor, which is more
>> noticeable.
>>
>> To fix this, revert the order of the commit operations back, and handle
>> runtime PM requirements in the CRTC .atomic_begin() and .atomic_enable()
>> helper operation handlers.
>>
>> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
>
> I only have code reduction or comment suggestions below - so either with or
> without those changes, feel free to add my:
>
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
>
>> ---
>> drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 66 ++++++++++++++++++++--------------
>> drivers/gpu/drm/rcar-du/rcar_du_crtc.h | 4 +--
>> drivers/gpu/drm/rcar-du/rcar_du_kms.c | 2 +-
>> 3 files changed, 43 insertions(+), 29 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
>> index 6b5219ef0ad2..76cdb88b2b8e 100644
>> --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
>> +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
>> @@ -448,14 +448,8 @@ static void rcar_du_crtc_wait_page_flip(struct rcar_du_crtc *rcrtc)
>> * Start/Stop and Suspend/Resume
>> */
>>
>> -static void rcar_du_crtc_start(struct rcar_du_crtc *rcrtc)
>> +static void rcar_du_crtc_setup(struct rcar_du_crtc *rcrtc)
>> {
>> - struct drm_crtc *crtc = &rcrtc->crtc;
>> - bool interlaced;
>> -
>> - if (rcrtc->started)
>> - return;
>> -
>> /* Set display off and background to black */
>> rcar_du_crtc_write(rcrtc, DOOR, DOOR_RGB(0, 0, 0));
>> rcar_du_crtc_write(rcrtc, BPOR, BPOR_RGB(0, 0, 0));
>> @@ -467,6 +461,18 @@ static void rcar_du_crtc_start(struct rcar_du_crtc *rcrtc)
>> /* Start with all planes disabled. */
>> rcar_du_group_write(rcrtc->group, rcrtc->index % 2 ? DS2PR : DS1PR, 0);
>>
>> + /* Enable the VSP compositor. */
>> + if (rcar_du_has(rcrtc->group->dev, RCAR_DU_FEATURE_VSP1_SOURCE))
>> + rcar_du_vsp_enable(rcrtc);
>> +
>> + /* Turn vertical blanking interrupt reporting on. */
>> + drm_crtc_vblank_on(&rcrtc->crtc);
>> +}
>> +
>> +static void rcar_du_crtc_start(struct rcar_du_crtc *rcrtc)
>> +{
>> + bool interlaced;
>> +
>> /* Select master sync mode. This enables display operation in master
>
> Are we close enough here to fix this multiline comment style ?
> (Not worth doing unless the patch is respun for other reasons ...)
>
> Actually - there are a lot in this file, so it would be better to do them all in
> one hit/patch at a point of least conflicts ...
>
>
>> * sync mode (with the HSYNC and VSYNC signals configured as outputs and
>> * actively driven).
>> @@ -477,24 +483,12 @@ static void rcar_du_crtc_start(struct rcar_du_crtc *rcrtc)
>> DSYSR_TVM_MASTER);
>>
>> rcar_du_group_start_stop(rcrtc->group, true);
>> -
>> - /* Enable the VSP compositor. */
>> - if (rcar_du_has(rcrtc->group->dev, RCAR_DU_FEATURE_VSP1_SOURCE))
>> - rcar_du_vsp_enable(rcrtc);
>> -
>> - /* Turn vertical blanking interrupt reporting back on. */
>> - drm_crtc_vblank_on(crtc);
>> -
>> - rcrtc->started = true;
>> }
>>
>> static void rcar_du_crtc_stop(struct rcar_du_crtc *rcrtc)
>> {
>> struct drm_crtc *crtc = &rcrtc->crtc;
>>
>> - if (!rcrtc->started)
>> - return;
>> -
>> /* Disable all planes and wait for the change to take effect. This is
>> * required as the DSnPR registers are updated on vblank, and no vblank
>> * will occur once the CRTC is stopped. Disabling planes when starting
>> @@ -525,8 +519,6 @@ static void rcar_du_crtc_stop(struct rcar_du_crtc *rcrtc)
>> rcar_du_crtc_clr_set(rcrtc, DSYSR, DSYSR_TVM_MASK, DSYSR_TVM_SWITCH);
>>
>> rcar_du_group_start_stop(rcrtc->group, false);
>> -
>> - rcrtc->started = false;
>> }
>>
>> void rcar_du_crtc_suspend(struct rcar_du_crtc *rcrtc)
>> @@ -546,12 +538,10 @@ void rcar_du_crtc_resume(struct rcar_du_crtc *rcrtc)
>> return;
>>
>> rcar_du_crtc_get(rcrtc);
>> - rcar_du_crtc_start(rcrtc);
>> + rcar_du_crtc_setup(rcrtc);
>
> Every call to _setup is immediately prefixed by a call to _get()
>
> Could the _get() be done in the _setup() for code reduction?
>
> I'm entirely open to that not happening here as it might be preferred to keep
> the _get() and _start() separate for style purposes.
>
>>
>> /* Commit the planes state. */
>> - if (rcar_du_has(rcrtc->group->dev, RCAR_DU_FEATURE_VSP1_SOURCE)) {
>> - rcar_du_vsp_enable(rcrtc);
>> - } else {
>> + if (!rcar_du_has(rcrtc->group->dev, RCAR_DU_FEATURE_VSP1_SOURCE)) {
>> for (i = 0; i < rcrtc->group->num_planes; ++i) {
>> struct rcar_du_plane *plane = &rcrtc->group->planes[i];
>>
>> @@ -563,6 +553,7 @@ void rcar_du_crtc_resume(struct rcar_du_crtc *rcrtc)
>> }
>>
>> rcar_du_crtc_update_planes(rcrtc);
>> + rcar_du_crtc_start(rcrtc);
>> }
>>
>> /* -----------------------------------------------------------------------------
>> @@ -574,7 +565,16 @@ static void rcar_du_crtc_atomic_enable(struct drm_crtc *crtc,
>> {
>> struct rcar_du_crtc *rcrtc = to_rcar_crtc(crtc);
>>
>> - rcar_du_crtc_get(rcrtc);
>> + /*
>> + * If the CRTC has already been setup by the .atomic_begin() handler we
>> + * can skip the setup stage.
>> + */
>> + if (!rcrtc->initialized) {
>> + rcar_du_crtc_get(rcrtc);
>> + rcar_du_crtc_setup(rcrtc);
>> + rcrtc->initialized = true;
>> + }
>> +
>> rcar_du_crtc_start(rcrtc);
>> }
>>
>> @@ -593,6 +593,7 @@ static void rcar_du_crtc_atomic_disable(struct drm_crtc *crtc,
>> }
>> spin_unlock_irq(&crtc->dev->event_lock);
>>
>> + rcrtc->initialized = false;
>> rcrtc->outputs = 0;
>> }
>>
>> @@ -601,6 +602,19 @@ static void rcar_du_crtc_atomic_begin(struct drm_crtc *crtc,
>> {
>> struct rcar_du_crtc *rcrtc = to_rcar_crtc(crtc);
>>
>> + WARN_ON(!crtc->state->enable);
>
> Is this necessary if it's handled by the rcrtc->initialized flag? or is it so
> that we find out if it happens ?
>
> (Or is this due to the re-ordering of the _commit_tail() function below?)
>
>
>> +
>> + /*
>> + * If a mode set is in progress we can be called with the CRTC disabled.
>> + * We then need to first setup the CRTC in order to configure planes.
>> + * The .atomic_enable() handler will notice and skip the CRTC setup.
>> + */
>
> I'm assuming this comment is the reason for the WARN_ON above ...
>
>
>> + if (!rcrtc->initialized) {
>> + rcar_du_crtc_get(rcrtc);
>> + rcar_du_crtc_setup(rcrtc);
>> + rcrtc->initialized = true;
>> + }
>
>
> If the _get() was moved into the _setup(), and _setup() was protected by the
> rcrtc->initialized flag, then _atomic_begin() _enable() and _resume() could all
> just simply call _setup(). The _resume() should only ever be called with
> rcrtc->initialized = false anyway, as that is set in _suspend()
>
>> +
>> if (rcar_du_has(rcrtc->group->dev, RCAR_DU_FEATURE_VSP1_SOURCE))
>> rcar_du_vsp_atomic_begin(rcrtc);
>> }
>> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h
>> index 0b6d26ecfc38..3cc376826592 100644
>> --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h
>> +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h
>> @@ -30,7 +30,7 @@ struct rcar_du_vsp;
>> * @extclock: external pixel dot clock (optional)
>> * @mmio_offset: offset of the CRTC registers in the DU MMIO block
>> * @index: CRTC software and hardware index
>> - * @started: whether the CRTC has been started and is running
>> + * @initialized: whether the CRTC has been initialized and clocks enabled
>> * @event: event to post when the pending page flip completes
>> * @flip_wait: wait queue used to signal page flip completion
>> * @outputs: bitmask of the outputs (enum rcar_du_output) driven by this CRTC
>> @@ -45,7 +45,7 @@ struct rcar_du_crtc {
>> struct clk *extclock;
>> unsigned int mmio_offset;
>> unsigned int index;
>> - bool started;
>> + bool initialized;
>>
>> struct drm_pending_vblank_event *event;
>> wait_queue_head_t flip_wait;
>> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
>> index 82b978a5dae6..c2f382feca07 100644
>> --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
>> +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
>> @@ -255,9 +255,9 @@ static void rcar_du_atomic_commit_tail(struct drm_atomic_state *old_state)
>>
>> /* Apply the atomic update. */
>> drm_atomic_helper_commit_modeset_disables(dev, old_state);
>> - drm_atomic_helper_commit_modeset_enables(dev, old_state);
>> drm_atomic_helper_commit_planes(dev, old_state,
>> DRM_PLANE_COMMIT_ACTIVE_ONLY);
>
> Except for DRM_PLANE_COMMIT_ACTIVE_ONLY, this function now looks very much like
> the default drm_atomic_helper_commit_tail() code.
>
> Reading around other uses /variants of commit_tail() style functions in other
> drivers has left me confused as to how the ordering affects things here.
>
> Could be worth adding a comment at least to describe why we can't use the
> default helper...
Or better still ... Use Maxime's new :
[PATCH 1/4] drm/atomic: implement drm_atomic_helper_commit_tail for runtime_pm users
>
>
>> + drm_atomic_helper_commit_modeset_enables(dev, old_state);
>> > drm_atomic_helper_commit_hw_done(old_state);
>> drm_atomic_helper_wait_for_vblanks(dev, old_state);
>>
