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

[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@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Cc: stable@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

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

[Sasha Levin]

Hi

[This is an automated email]

This commit has been processed because it contains a "Fixes:" tag
fixing commit: a6cc417d3eee ("drm: rcar-du: Turn LVDS clock output on/off for DPAD0 output on D3/E3").

The bot has tested the following trees: v5.8.10, v5.4.66.

v5.8.10: Build OK!
v5.4.66: Failed to apply! Possible dependencies:
    35a61fe9218a ("drm: Stop accessing encoder->bridge directly")
    62afb4ad425a ("drm/connector: Allow max possible encoders to attach to a connector")
    89958b7cd955 ("drm/bridge: panel: Infer connector type from panel by default")
    a92462d6bf49 ("drm/connector: Share with non-atomic drivers the function to get the single encoder")
    ea099adfdf4b ("drm/bridge: Rename bridge helpers targeting a bridge chain")
    fadf872d9d92 ("drm/bridge: Introduce drm_bridge_get_next_bridge()")
    fe9e557dfb48 ("drm/bridge: Fix references to drm_bridge_funcs in documentation")


NOTE: The patch will not be queued to stable trees until it is upstream.

How should we proceed with this patch?

-- 
Thanks
Sasha