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,