On 13/07/17 16:51, Kieran Bingham wrote:
> 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
Never mind - I've just looked again, and seen that this new helper function is
the ordering previous to *this* patch, and therefore isn't the same.
However - it's worth noting that Maxime's patch converts this function to the
new helper - which contradicts this patch's motivations.
>>
>>
>>> + 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);
>>>
