[PATCH] drm: rcar-du: Fix LVDS dual link mode kernel crash

[Biju Das]

Kernel crash is observed when dual lvds link mode is activated
along with HDMI. For this use case DU0 drives dual lvds output
and DU1 drives hdmi output, but dot clock for DU1 is generated
from lvds1.

[  585.890230] Unable to handle kernel paging request at virtual address ffffffffffffff18
[  585.898534] Mem abort info:
[  586.065713] x1 : 000000000839b680 x0 : ffffffffffffff20
[  586.071038] Call trace:
[  586.073490]  rcar_lvds_clk_enable+0x14/0xd0
[  586.077682]  rcar_du_crtc_atomic_enable+0xe4/0xe8
[  586.082403]  drm_atomic_helper_commit_modeset_enables+0x1f0/0x240
[  586.088508]  rcar_du_atomic_commit_tail+0xac/0xd8
[  586.093224]  commit_tail+0x9c/0x168
[  586.096720]  drm_atomic_helper_commit+0x180/0x198
[  586.101435]  drm_atomic_commit+0x48/0x58
[  586.105370]  drm_client_modeset_commit_atomic+0x250/0x2b0
[  586.110780]  drm_client_modeset_commit_locked+0x54/0x1e8
[  586.116102]  drm_client_modeset_commit+0x2c/0x50
[  586.120733]  __drm_fb_helper_restore_fbdev_mode_unlocked+0x88/0x120
[  586.127013]  drm_fb_helper_set_par+0x38/0x70
[  586.131291]  drm_fb_helper_hotplug_event.part.22+0xc4/0xd8
[  586.136789]  drm_fbdev_client_hotplug+0xcc/0x1d8
[  586.141415]  drm_client_dev_hotplug+0x7c/0xc0
[  586.145781]  drm_kms_helper_hotplug_event+0x30/0x40
[  586.150670]  tda998x_detect_work+0x14/0x28
[  586.154781]  process_one_work+0x2a8/0x730

Fixes: a6cc417d3eee ("drm: rcar-du: Turn LVDS clock output on/off for DPAD0
output on D3/E3")
Signed-off-by: Biju Das <biju.das.jz at bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj at bp.renesas.com>
Cc: stable at vger.kernel.org
---
 drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 14 ++++++++++++--
 drivers/gpu/drm/rcar-du/rcar_lvds.c    |  6 ++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
index fe86a3e67757..2440df786b02 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
@@ -729,11 +729,16 @@ static void rcar_du_crtc_atomic_enable(struct drm_crtc *crtc,
 	    rstate->outputs == BIT(RCAR_DU_OUTPUT_DPAD0)) {
 		struct rcar_du_encoder *encoder =
 			rcdu->encoders[RCAR_DU_OUTPUT_LVDS0 + rcrtc->index];
+		struct rcar_du_encoder *enc_dual_link =
+			rcdu->encoders[RCAR_DU_OUTPUT_LVDS0];
 		const struct drm_display_mode *mode =
 			&crtc->state->adjusted_mode;
 		struct drm_bridge *bridge;
 
-		bridge = drm_bridge_chain_get_first_bridge(&encoder->base);
+		bridge = drm_bridge_chain_get_first_bridge(&enc_dual_link->base);
+		if (!rcar_lvds_dual_link(bridge))
+			bridge = drm_bridge_chain_get_first_bridge(&encoder->base);
+
 		rcar_lvds_clk_enable(bridge, mode->clock * 1000);
 	}
 
@@ -761,13 +766,18 @@ static void rcar_du_crtc_atomic_disable(struct drm_crtc *crtc,
 	    rstate->outputs == BIT(RCAR_DU_OUTPUT_DPAD0)) {
 		struct rcar_du_encoder *encoder =
 			rcdu->encoders[RCAR_DU_OUTPUT_LVDS0 + rcrtc->index];
+		struct rcar_du_encoder *enc_dual_link =
+			rcdu->encoders[RCAR_DU_OUTPUT_LVDS0];
 		struct drm_bridge *bridge;
 
 		/*
 		 * Disable the LVDS clock output, see
 		 * rcar_du_crtc_atomic_enable().
 		 */
-		bridge = drm_bridge_chain_get_first_bridge(&encoder->base);
+		bridge = drm_bridge_chain_get_first_bridge(&enc_dual_link->base);
+		if (!rcar_lvds_dual_link(bridge))
+			bridge = drm_bridge_chain_get_first_bridge(&encoder->base);
+
 		rcar_lvds_clk_disable(bridge);
 	}
 
diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
index ab0d49618cf9..588f2a16b8a5 100644
--- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
+++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
@@ -373,6 +373,9 @@ int rcar_lvds_clk_enable(struct drm_bridge *bridge, unsigned long freq)
 	struct rcar_lvds *lvds = bridge_to_rcar_lvds(bridge);
 	int ret;
 
+	if (lvds->link_type != RCAR_LVDS_SINGLE_LINK && lvds->companion)
+		lvds = bridge_to_rcar_lvds(lvds->companion);
+
 	if (WARN_ON(!(lvds->info->quirks & RCAR_LVDS_QUIRK_EXT_PLL)))
 		return -ENODEV;
 
@@ -392,6 +395,9 @@ void rcar_lvds_clk_disable(struct drm_bridge *bridge)
 {
 	struct rcar_lvds *lvds = bridge_to_rcar_lvds(bridge);
 
+	if (lvds->link_type != RCAR_LVDS_SINGLE_LINK && lvds->companion)
+		lvds = bridge_to_rcar_lvds(lvds->companion);
+
 	if (WARN_ON(!(lvds->info->quirks & RCAR_LVDS_QUIRK_EXT_PLL)))
 		return;
 
-- 
2.17.1