Re: [PATCH] drm/msm/dp: update is_connected status base on sink count at dp_pm_resume()

[khsieh]

On 2021-07-30 11:57, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2021-07-28 14:30:54)
> > Currently at dp_pm_resume() is_connected state is decided base on hpd 
> > connection
> > status only. This will put is_connected in wrongly "true" state at the 
> > scenario
> > that dongle attached to DUT but without hmdi cable connecting to it. 
> > Fix this
> > problem by adding read sink count from dongle and decided is_connected 
> > state base
> > on both sink count and hpd connection status.
>
> Please add a Fixes tag.
>
> > Signed-off-by: Kuogee Hsieh <khsieh@xxxxxxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/msm/dp/dp_display.c | 23 +++++++++++++++++++++--
> >  1 file changed, 21 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c 
> > b/drivers/gpu/drm/msm/dp/dp_display.c
> > index 2b660e9..9bcb261 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > @@ -1308,6 +1308,17 @@ static int dp_display_remove(struct 
> > platform_device *pdev)
> >         return 0;
> >  }
> >
> > +static int dp_get_sink_count(struct dp_display_private *dp)
> > +{
> > +       u8 sink_count;
> > +
> > +       sink_count = drm_dp_read_sink_count(dp->aux);
>
> drm_dp_read_sink_count() returns an int, not a u8. Comparing a u8 to
> less than zero doesn't make any sense as it isn't signed.
>
> > +       if (sink_count < 0)
> > +               return 0;
> > +
> > +       return sink_count;
> > +}
>
> We can drop this function and just have an int count in dp_pm_resume()
> that is compared to < 0 and then ignored.
>
> > +
> >  static int dp_pm_resume(struct device *dev)
> >  {
> >         struct platform_device *pdev = to_platform_device(dev);
> > @@ -1327,14 +1338,22 @@ static int dp_pm_resume(struct device *dev)
> >
> >         dp_catalog_ctrl_hpd_config(dp->catalog);
> >
> > -       status = dp_catalog_link_is_connected(dp->catalog);
> > +       /*
> > +        * set sink to normal operation mode -- D0
> > +        * before dpcd read
> > +        */
> > +       dp_link_psm_config(dp->link, &dp->panel->link_info, false);
> >
> > +       if ((status = dp_catalog_link_is_connected(dp->catalog)))
> > +               dp->link->sink_count = dp_get_sink_count(dp);
>
> Do we need to call drm_dp_read_sink_count_cap() as well?
no, we only need sink_count
> > +       else
> > +               dp->link->sink_count = 0;
> >         /*
> >          * can not declared display is connected unless
> >          * HDMI cable is plugged in and sink_count of
> >          * dongle become 1
> >          */
> > -       if (status && dp->link->sink_count)
>
> Is 'status' used anymore? If not, please remove it.
Yes, it still used which used to decided to perform dpcd read sink count 
or not
> > +       if (dp->link->sink_count)
> >                 dp->dp_display.is_connected = true;
> >         else
> >                 dp->dp_display.is_connected = false;