[PATCH] drm: bridge: it66121: Added it66121 chip external screen status judgment

[Yunlongli]

In the actual tests,  the IT66121 chip sometimes misjudged whether
it had an external screen, so, reference the it66121_user_guid.pdf
about Audio/Video data is stable or not A typical initialization
of HDMI link should be based on interrupt signal and appropriate
register probing. Recommended flow is detailed in IT66121
Programming Guide. Simply put, the microcontroller should monitor
the HPD status first. Upon valid HPD event, move on to check
RxSENDetect register to see if the receiver chip is ready for
further handshaking. When RxSENDetect is asserted, start reading EDID
data through DDC channels and carry on the rest of the handshaking
subsequently.If the micro-controller makes no use of the interrupt
signal as well as the above-mentioned status  registers, the link
establishment might fail. Please do follow the suggested
initialization flow recommended in IT66121 Programming Guide.
So, I add the IT66121_SYS_STATUS_SENDECTECT register status detection.

Signed-off-by: Yunlongli <liyunlonga at uniontech.com>
---
 drivers/gpu/drm/bridge/ite-it66121.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/ite-it66121.c b/drivers/gpu/drm/bridge/ite-it66121.c
index 2f2a09adb4bc..9ed4fa298d11 100644
--- a/drivers/gpu/drm/bridge/ite-it66121.c
+++ b/drivers/gpu/drm/bridge/ite-it66121.c
@@ -523,7 +523,7 @@ static bool it66121_is_hpd_detect(struct it66121_ctx *ctx)
 	if (regmap_read(ctx->regmap, IT66121_SYS_STATUS_REG, &val))
 		return false;
 
-	return val & IT66121_SYS_STATUS_HPDETECT;
+	return ((val & IT66121_SYS_STATUS_HPDETECT) && (val & IT66121_SYS_STATUS_SENDECTECT));
 }
 
 static int it66121_bridge_attach(struct drm_bridge *bridge,
-- 
2.20.1