[PATCH] drm/imx: imx-ldb: store LVDS bus configuration in ldb channel

[Philipp Zabel]

The code in imx_ldb_encoder_mode_set crashes trying to access the
crtc->state->state drm_atomic_state pointer if that was previously
cleared by drm_atomic_helper_swap_state.
Instead of trying to walk all connectors during encoder mode_set to
determine the LVDS bus format from panel or external bridge connector
display info, store it in imx_crtc_state during encoder atomic_check,
where it is already known, and just retrieve it from imx_crtc_state
during encoder mode_set.

Fixes: 49f98bc4d44a4 ("drm/imx: store internal bus configuration in crtc state")
Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>
---
 drivers/gpu/drm/imx/imx-drm.h |  1 +
 drivers/gpu/drm/imx/imx-ldb.c | 22 +++++-----------------
 2 files changed, 6 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/imx/imx-drm.h b/drivers/gpu/drm/imx/imx-drm.h
index bdaa381..5e2f68a 100644
--- a/drivers/gpu/drm/imx/imx-drm.h
+++ b/drivers/gpu/drm/imx/imx-drm.h
@@ -19,6 +19,7 @@ struct imx_crtc_state {
 	u32					bus_flags;
 	int					di_hsync_pin;
 	int					di_vsync_pin;
+	u32					ldb_bus_format;
 };
 
 static inline struct imx_crtc_state *to_imx_crtc_state(struct drm_crtc_state *s)
diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
index dc2b420..871dff9 100644
--- a/drivers/gpu/drm/imx/imx-ldb.c
+++ b/drivers/gpu/drm/imx/imx-ldb.c
@@ -262,7 +262,10 @@ static void imx_ldb_encoder_mode_set(struct drm_encoder *encoder,
 	unsigned long serial_clk;
 	unsigned long di_clk = mode->clock * 1000;
 	int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
-	u32 bus_format = imx_ldb_ch->bus_format;
+	struct drm_crtc_state *crtc_state = encoder->crtc->state;
+	struct imx_crtc_state *imx_crtc_state = to_imx_crtc_state(crtc_state);
+	u32 bus_format = imx_ldb_ch->bus_format ?:
+			 imx_crtc_state->ldb_bus_format;
 
 	if (mode->clock > 170000) {
 		dev_warn(ldb->dev,
@@ -297,22 +300,6 @@ static void imx_ldb_encoder_mode_set(struct drm_encoder *encoder,
 			ldb->ldb_ctrl &= ~LDB_DI1_VS_POL_ACT_LOW;
 	}
 
-	if (!bus_format) {
-		struct drm_connector_state *conn_state;
-		struct drm_connector *connector;
-		int i;
-
-		for_each_connector_in_state(encoder->crtc->state->state,
-					    connector, conn_state, i) {
-			struct drm_display_info *di = &connector->display_info;
-
-			if (conn_state->crtc == encoder->crtc &&
-			    di->num_bus_formats) {
-				bus_format = di->bus_formats[0];
-				break;
-			}
-		}
-	}
 	imx_ldb_ch_set_bus_format(imx_ldb_ch, bus_format);
 }
 
@@ -404,6 +391,7 @@ static int imx_ldb_encoder_atomic_check(struct drm_encoder *encoder,
 
 	imx_crtc_state->di_hsync_pin = 2;
 	imx_crtc_state->di_vsync_pin = 3;
+	imx_crtc_state->ldb_bus_format = bus_format;
 
 	return 0;
 }
-- 
2.8.1