linux-kernel - Re: [PATCH] lontium-lt9611: check a different register bit for HDMI sensing

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Message-ID: <YZSOcBz+W9ORXf1z@matsya>
Date:   Wed, 17 Nov 2021 10:39:04 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Anibal Limon <anibal.limon@...aro.org>
Cc:     Peter Collingbourne <pcc@...gle.com>,
        Robert Foss <robert.foss@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: Re: [PATCH] lontium-lt9611: check a different register bit for HDMI
 sensing

On 16-11-21, 22:49, Anibal Limon wrote:
> Dmitry,
> 
> May be this is the reason of my HP monitor not working in RB5.

Rb5 has Lt9611UXC


> 
> Regards,
> Anibal
> 
> El mar., 16 de noviembre de 2021 20:07, Peter Collingbourne <pcc@...gle.com>
> escribió:
> 
> > It has been observed that with certain monitors such as the HP Z27n,
> > the register 0x825e reads a value of 0x79 when the HDMI cable is
> > connected and 0x78 when it is disconnected, i.e. bit 0 appears
> > to correspond to the HDMI connection status and bit 2 is never
> > set. Therefore, change the driver to check bit 0 instead of bit 2.
> >
> > Signed-off-by: Peter Collingbourne <pcc@...gle.com>
> > Link:
> > https://linux-review.googlesource.com/id/I7e76411127e1ce4988a3f6d0c8ba5f1c3d880c23
> > ---
> > N.B. I don't currently have easy access to a monitor that works
> > with the existing driver, so it would be great if people with
> > monitors that currently work could test this patch to make sure
> > that it doesn't introduce any regressions. Otherwise I will change
> > it to check both bits.
> >
> >  drivers/gpu/drm/bridge/lontium-lt9611.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c
> > b/drivers/gpu/drm/bridge/lontium-lt9611.c
> > index 29b1ce2140ab..71f1db802916 100644
> > --- a/drivers/gpu/drm/bridge/lontium-lt9611.c
> > +++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
> > @@ -586,7 +586,7 @@ lt9611_connector_detect(struct drm_connector
> > *connector, bool force)
> >         int connected = 0;
> >
> >         regmap_read(lt9611->regmap, 0x825e, &reg_val);
> > -       connected  = (reg_val & BIT(2));
> > +       connected  = (reg_val & BIT(0));
> >
> >         lt9611->status = connected ?  connector_status_connected :
> >                                 connector_status_disconnected;
> > @@ -926,7 +926,7 @@ static enum drm_connector_status
> > lt9611_bridge_detect(struct drm_bridge *bridge)
> >         int connected;
> >
> >         regmap_read(lt9611->regmap, 0x825e, &reg_val);
> > -       connected  = reg_val & BIT(2);
> > +       connected  = reg_val & BIT(0);
> >
> >         lt9611->status = connected ?  connector_status_connected :
> >                                 connector_status_disconnected;
> > --
> > 2.34.0.rc1.387.gb447b232ab-goog
> >
> >

-- 
~Vinod