[PATCH v2 1/3] drm/atomic-helper: rcar-du: Enable CRTC early on R-Car DU

[Linus Walleij <linus.walleij@linaro.org>]

From: Marek Vasut <marek.vasut+renesas@mailbox.org>

Introduce a variant of drm_atomic_helper_commit_modeset_enables()
which enables CRTC before encoder/bridge. This is needed on R-Car DU,
where the CRTC provides clock to LVDS and DSI, and has to be started
before a bridge may call .prepare , which may trigger e.g. DSI transfer.

This specifically fixes the case where ILI9881C is connected to R-Car
DU DSI. The ILI9881C panel driver does DSI command transfer in its
struct drm_panel_funcs .prepare function, which is currently called
before R-Car DU rcar_du_crtc_atomic_enable() rcar_mipi_dsi_pclk_enable()
and the DSI command transfer times out.

Fix this by restoring the enable ordering introduced in commit
c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain pre-enable
and post-disable"), to enable CRTC early.

Fixes: c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain pre-enable and post-disable")
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
---
 drivers/gpu/drm/drm_atomic_helper.c           | 24 ++++++++++++++++++++++++
 drivers/gpu/drm/renesas/rcar-du/rcar_du_kms.c |  2 +-
 include/drm/drm_atomic_helper.h               |  2 ++
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index d5ebe6ea0acb..f03b93c72b8f 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1692,6 +1692,30 @@ void drm_atomic_helper_commit_modeset_enables(struct drm_device *dev,
 }
 EXPORT_SYMBOL(drm_atomic_helper_commit_modeset_enables);
 
+/**
+ * drm_atomic_helper_commit_modeset_enables_crtc_early - modeset commit to enable outputs, start CRTC early
+ * @dev: DRM device
+ * @state: atomic state object being committed
+ *
+ * This function is a variant of drm_atomic_helper_commit_modeset_enables()
+ * which enables CRTC before encoder/bridge. This is needed on R-Car DU,
+ * where the CRTC provides clock to LVDS and DSI, and has to be started
+ * before a bridge may call .prepare , which may trigger e.g. DSI transfer.
+ */
+void
+drm_atomic_helper_commit_modeset_enables_crtc_early(struct drm_device *dev,
+						    struct drm_atomic_state *state)
+{
+	crtc_enable(dev, state);
+
+	encoder_bridge_pre_enable(dev, state);
+
+	encoder_bridge_enable(dev, state);
+
+	drm_atomic_helper_commit_writebacks(dev, state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_commit_modeset_enables_crtc_early);
+
 /*
  * For atomic updates which touch just a single CRTC, calculate the time of the
  * next vblank, and inform all the fences of the deadline.
diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/renesas/rcar-du/rcar_du_kms.c
index 216219accfd9..b2403be4436b 100644
--- a/drivers/gpu/drm/renesas/rcar-du/rcar_du_kms.c
+++ b/drivers/gpu/drm/renesas/rcar-du/rcar_du_kms.c
@@ -544,7 +544,7 @@ static void rcar_du_atomic_commit_tail(struct drm_atomic_state *old_state)
 	drm_atomic_helper_commit_modeset_disables(dev, old_state);
 	drm_atomic_helper_commit_planes(dev, old_state,
 					DRM_PLANE_COMMIT_ACTIVE_ONLY);
-	drm_atomic_helper_commit_modeset_enables(dev, old_state);
+	drm_atomic_helper_commit_modeset_enables_crtc_early(dev, old_state);
 
 	drm_atomic_helper_commit_hw_done(old_state);
 	drm_atomic_helper_wait_for_flip_done(dev, old_state);
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index 53382fe93537..d7fb473db343 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -93,6 +93,8 @@ void drm_atomic_helper_commit_modeset_disables(struct drm_device *dev,
 					       struct drm_atomic_state *state);
 void drm_atomic_helper_commit_modeset_enables(struct drm_device *dev,
 					  struct drm_atomic_state *old_state);
+void drm_atomic_helper_commit_modeset_enables_crtc_early(struct drm_device *dev,
+							 struct drm_atomic_state *old_state);
 
 int drm_atomic_helper_prepare_planes(struct drm_device *dev,
 				     struct drm_atomic_state *state);

-- 
2.51.1