2022-05-11 04:29:34

by John Stultz

Subject: [PATCH 2/2] drm/bridge: lt9611: Use both bits for HDMI sensing

In commit 19cf41b64e3b ("lontium-lt9611: check a different
register bit for HDMI sensing"), the bit flag used to detect
HDMI cable connect was switched from BIT(2) to BIT(0) to improve
compatibility with some monitors that didn't seem to set BIT(2).

However, with that change, I've seen occasional issues where the
detection failed, because BIT(2) was set, but not BIT(0).

Unfortunately, as I understand it, the bits and their function
was never clearly documented. So lets instead check both
(BIT(2) | BIT(0)) when checking the register.

Cc: Yongqin Liu <[email protected]>
Cc: Amit Pundir <[email protected]>
Cc: Peter Collingbourne <[email protected]>
Cc: Vinod Koul <[email protected]>
Cc: Bjorn Andersson <[email protected]>
Cc: Robert Foss <[email protected]>
Cc: [email protected]
Fixes: 19cf41b64e3b ("lontium-lt9611: check a different register bit for HDMI sensing")
Signed-off-by: John Stultz <[email protected]>
---
drivers/gpu/drm/bridge/lontium-lt9611.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c
index bf66af668f61..a11604a56e08 100644
--- a/drivers/gpu/drm/bridge/lontium-lt9611.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
@@ -584,7 +584,7 @@ static enum drm_connector_status __lt9611_detect(struct lt9611 *lt9611)
int connected = 0;

regmap_read(lt9611->regmap, 0x825e, &reg_val);
- connected = (reg_val & BIT(0));
+ connected = (reg_val & (BIT(2) | BIT(0)));

lt9611->status = connected ? connector_status_connected :
connector_status_disconnected;
--
2.36.0.512.ge40c2bad7a-goog

2022-05-23 10:19:23

by Robert Foss

Subject: Re: [PATCH 2/2] drm/bridge: lt9611: Use both bits for HDMI sensing

On Wed, 11 May 2022 at 03:26, John Stultz <[email protected]> wrote:
>
> In commit 19cf41b64e3b ("lontium-lt9611: check a different
> register bit for HDMI sensing"), the bit flag used to detect
> HDMI cable connect was switched from BIT(2) to BIT(0) to improve
> compatibility with some monitors that didn't seem to set BIT(2).
>
> However, with that change, I've seen occasional issues where the
> detection failed, because BIT(2) was set, but not BIT(0).

I was waiting for a review or testing from a previous lt9611
committer, but seeing as how functionality is being re-introduced in
this patch I think a code review is all that's needed.

>
> Unfortunately, as I understand it, the bits and their function
> was never clearly documented. So lets instead check both
> (BIT(2) | BIT(0)) when checking the register.
>
> Cc: Yongqin Liu <[email protected]>
> Cc: Amit Pundir <[email protected]>
> Cc: Peter Collingbourne <[email protected]>
> Cc: Vinod Koul <[email protected]>
> Cc: Bjorn Andersson <[email protected]>
> Cc: Robert Foss <[email protected]>
> Cc: [email protected]
> Fixes: 19cf41b64e3b ("lontium-lt9611: check a different register bit for HDMI sensing")
> Signed-off-by: John Stultz <[email protected]>
> ---
> drivers/gpu/drm/bridge/lontium-lt9611.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c
> index bf66af668f61..a11604a56e08 100644
> --- a/drivers/gpu/drm/bridge/lontium-lt9611.c
> +++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
> @@ -584,7 +584,7 @@ static enum drm_connector_status __lt9611_detect(struct lt9611 *lt9611)
> int connected = 0;
>
> regmap_read(lt9611->regmap, 0x825e, &reg_val);
> - connected = (reg_val & BIT(0));
> + connected = (reg_val & (BIT(2) | BIT(0)));
>
> lt9611->status = connected ? connector_status_connected :
> connector_status_disconnected;
> --
> 2.36.0.512.ge40c2bad7a-goog
>

I reviewed this series and it looks good.

Reviewed-by: Robert Foss <[email protected]>

Applied to drm-misc-next.