drm/msm: add kms->flush_commit()

Add ->flush_commit(crtc_mask).  Currently a no-op, but kms backends
should migrate writing flush registers to this hook, so we can decouple
pushing updates to hardware, and flushing the updates.

Once we add async commit support, the hw updates will be pushed down to
the hw synchronously, but flushing the updates will be deferred until as
close to vblank as possible, so that multiple updates can be combined in
a single frame.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Sean Paul <sean@poorly.run>

drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c

@@ -280,6 +280,11 @@ static void dpu_kms_prepare_commit(struct msm_kms *kms,
 	}
 }
 
+static void dpu_kms_flush_commit(struct msm_kms *kms, unsigned crtc_mask)
+{
+	/* TODO */
+}
+
 /*
  * Override the encoder enable since we need to setup the inline rotator and do
  * some crtc magic before enabling any bridge that might be present.
@@ -680,6 +685,7 @@ static const struct msm_kms_funcs kms_funcs = {
 	.irq_uninstall   = dpu_irq_uninstall,
 	.irq             = dpu_irq,
 	.prepare_commit  = dpu_kms_prepare_commit,
+	.flush_commit    = dpu_kms_flush_commit,
 	.commit          = dpu_kms_commit,
 	.wait_flush      = dpu_kms_wait_flush,
 	.complete_commit = dpu_kms_complete_commit,

drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c

@@ -110,6 +110,11 @@ static void mdp4_prepare_commit(struct msm_kms *kms, struct drm_atomic_state *st
 		drm_crtc_vblank_get(crtc);
 }
 
+static void mdp4_flush_commit(struct msm_kms *kms, unsigned crtc_mask)
+{
+	/* TODO */
+}
+
 static void mdp4_wait_flush(struct msm_kms *kms, unsigned crtc_mask)
 {
 	struct mdp4_kms *mdp4_kms = to_mdp4_kms(to_mdp_kms(kms));
@@ -181,6 +186,7 @@ static const struct mdp_kms_funcs kms_funcs = {
 		.enable_vblank   = mdp4_enable_vblank,
 		.disable_vblank  = mdp4_disable_vblank,
 		.prepare_commit  = mdp4_prepare_commit,
+		.flush_commit    = mdp4_flush_commit,
 		.wait_flush      = mdp4_wait_flush,
 		.complete_commit = mdp4_complete_commit,
 		.get_format      = mdp_get_format,

drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c

@@ -160,6 +160,11 @@ static void mdp5_prepare_commit(struct msm_kms *kms, struct drm_atomic_state *st
 		mdp5_smp_prepare_commit(mdp5_kms->smp, &global_state->smp);
 }
 
+static void mdp5_flush_commit(struct msm_kms *kms, unsigned crtc_mask)
+{
+	/* TODO */
+}
+
 static void mdp5_wait_flush(struct msm_kms *kms, unsigned crtc_mask)
 {
 	struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(kms));
@@ -278,6 +283,7 @@ static const struct mdp_kms_funcs kms_funcs = {
 		.irq             = mdp5_irq,
 		.enable_vblank   = mdp5_enable_vblank,
 		.disable_vblank  = mdp5_disable_vblank,
+		.flush_commit    = mdp5_flush_commit,
 		.prepare_commit  = mdp5_prepare_commit,
 		.wait_flush      = mdp5_wait_flush,
 		.complete_commit = mdp5_complete_commit,

drivers/gpu/drm/msm/msm_atomic.c

@@ -51,16 +51,21 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
 
 	kms->funcs->prepare_commit(kms, state);
 
+	/*
+	 * Push atomic updates down to hardware:
+	 */
 	drm_atomic_helper_commit_modeset_disables(dev, state);
-
 	drm_atomic_helper_commit_planes(dev, state, 0);
-
 	drm_atomic_helper_commit_modeset_enables(dev, state);
 
+	/*
+	 * Flush hardware updates:
+	 */
 	if (kms->funcs->commit) {
 		DRM_DEBUG_ATOMIC("triggering commit\n");
 		kms->funcs->commit(kms, state);
 	}
+	kms->funcs->flush_commit(kms, crtc_mask);
 
 	kms->funcs->wait_flush(kms, crtc_mask);
 	kms->funcs->complete_commit(kms, crtc_mask);

drivers/gpu/drm/msm/msm_kms.h

@@ -30,12 +30,47 @@ struct msm_kms_funcs {
 	irqreturn_t (*irq)(struct msm_kms *kms);
 	int (*enable_vblank)(struct msm_kms *kms, struct drm_crtc *crtc);
 	void (*disable_vblank)(struct msm_kms *kms, struct drm_crtc *crtc);
-	/* modeset, bracketing atomic_commit(): */
+
+	/*
+	 * Atomic commit handling:
+	 */
+
+	/**
+	 * Prepare for atomic commit.  This is called after any previous
+	 * (async or otherwise) commit has completed.
+	 */
 	void (*prepare_commit)(struct msm_kms *kms, struct drm_atomic_state *state);
+
+	/**
+	 * Flush an atomic commit.  This is called after the hardware
+	 * updates have already been pushed down to effected planes/
+	 * crtcs/encoders/connectors.
+	 */
+	void (*flush_commit)(struct msm_kms *kms, unsigned crtc_mask);
+
+	/* TODO remove ->commit(), use ->flush_commit() instead: */
 	void (*commit)(struct msm_kms *kms, struct drm_atomic_state *state);
-	void (*complete_commit)(struct msm_kms *kms, unsigned crtc_mask);
+
+	/**
+	 * Wait for any in-progress flush to complete on the specified
+	 * crtcs.  This should not block if there is no in-progress
+	 * commit (ie. don't just wait for a vblank), as it will also
+	 * be called before ->prepare_commit() to ensure any potential
+	 * "async" commit has completed.
+	 */
 	void (*wait_flush)(struct msm_kms *kms, unsigned crtc_mask);
 
+	/**
+	 * Clean up after commit is completed.  This is called after
+	 * ->wait_flush(), to give the backend a chance to do any
+	 * post-commit cleanup.
+	 */
+	void (*complete_commit)(struct msm_kms *kms, unsigned crtc_mask);
+
+	/*
+	 * Format handling:
+	 */
+
 	/* get msm_format w/ optional format modifiers from drm_mode_fb_cmd2 */
 	const struct msm_format *(*get_format)(struct msm_kms *kms,
 					const uint32_t format,
@@ -45,6 +80,7 @@ struct msm_kms_funcs {
 			const struct msm_format *msm_fmt,
 			const struct drm_mode_fb_cmd2 *cmd,
 			struct drm_gem_object **bos);
+
 	/* misc: */
 	long (*round_pixclk)(struct msm_kms *kms, unsigned long rate,
 			struct drm_encoder *encoder);