[PATCH] drm/bridge: ti-sn65dsi83: Check link status register after enabling the bridge

[Marek Vasut]

In rare cases, the bridge may not start up correctly, which usually
leads to no display output. In case this happens, warn about it in
the kernel log.

Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Jagan Teki <jagan at amarulasolutions.com>
Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Cc: Linus Walleij <linus.walleij at linaro.org>
Cc: Robert Foss <robert.foss at linaro.org>
Cc: Sam Ravnborg <sam at ravnborg.org>
Cc: dri-devel at lists.freedesktop.org
---
NOTE: See the following:
https://e2e.ti.com/support/interface-group/interface/f/interface-forum/942005/sn65dsi83-dsi83-lvds-bridge---sporadic-behavior---no-video
https://community.nxp.com/t5/i-MX-Processors/i-MX8M-MIPI-DSI-Interface-LVDS-Bridge-Initialization/td-p/1156533
---
 drivers/gpu/drm/bridge/ti-sn65dsi83.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
index a32f70bc68ea4..4ea71d7f0bfbc 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
@@ -520,6 +520,11 @@ static void sn65dsi83_atomic_enable(struct drm_bridge *bridge,
 	/* Clear all errors that got asserted during initialization. */
 	regmap_read(ctx->regmap, REG_IRQ_STAT, &pval);
 	regmap_write(ctx->regmap, REG_IRQ_STAT, pval);
+
+	usleep_range(10000, 12000);
+	regmap_read(ctx->regmap, REG_IRQ_STAT, &pval);
+	if (pval)
+		dev_err(ctx->dev, "Unexpected link status 0x%02x\n", pval);
 }
 
 static void sn65dsi83_atomic_disable(struct drm_bridge *bridge,
-- 
2.33.0