linux-kernel - Re: [PATCH 05/15] drm/vc4: hdmi: Restore cec physical address on reconnect

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Date:   Fri, 18 Dec 2020 14:45:54 +0000
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Eric Anholt <eric@...olt.net>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Jason Cooper <jason@...edaemon.net>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org,
        Marc Zyngier <maz@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        LKML <linux-kernel@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-rpi-kernel@...ts.infradead.org,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Dom Cobley <popcornmix@...il.com>
Subject: Re: [PATCH 05/15] drm/vc4: hdmi: Restore cec physical address on reconnect

On Fri, 18 Dec 2020 at 14:21, Dave Stevenson
<dave.stevenson@...pberrypi.com> wrote:
>
> Hi  Maxime & Dom
>
> On Thu, 10 Dec 2020 at 13:47, Maxime Ripard <maxime@...no.tech> wrote:
> >
> > From: Dom Cobley <popcornmix@...il.com>
> >
> > Currently we call cec_phys_addr_invalidate on a hotplug deassert.
> > That may be due to a TV power cycling, or an AVR being switched
> > on (and switching edid).
> >
> > This makes CEC unusable since our controller wouldn't have a physical
> > address anymore.
> >
> > Set it back up again on the hotplug assert.
> >
> > Fixes: 15b4511a4af6 ("drm/vc4: add HDMI CEC support")
> > Signed-off-by: Dom Cobley <popcornmix@...il.com>
> > Signed-off-by: Maxime Ripard <maxime@...no.tech>
> > ---
> >  drivers/gpu/drm/vc4/vc4_hdmi.c | 25 +++++++++++++++++--------
> >  1 file changed, 17 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> > index 28b78ea885ea..eff3bac562c6 100644
> > --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> > +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> > @@ -136,20 +136,29 @@ static enum drm_connector_status
> >  vc4_hdmi_connector_detect(struct drm_connector *connector, bool force)
> >  {
> >         struct vc4_hdmi *vc4_hdmi = connector_to_vc4_hdmi(connector);
> > +       bool connected = false;
> >
> >         if (vc4_hdmi->hpd_gpio) {
> >                 if (gpio_get_value_cansleep(vc4_hdmi->hpd_gpio) ^
> >                     vc4_hdmi->hpd_active_low)
> > -                       return connector_status_connected;
> > -               cec_phys_addr_invalidate(vc4_hdmi->cec_adap);
> > -               return connector_status_disconnected;
> > -       }
> > -
> > -       if (drm_probe_ddc(vc4_hdmi->ddc))
> > -               return connector_status_connected;
> > -
> > +                       connected = true;
> > +       } else if (drm_probe_ddc(vc4_hdmi->ddc))
> > +               connected = true;
> >         if (HDMI_READ(HDMI_HOTPLUG) & VC4_HDMI_HOTPLUG_CONNECTED)
>
> This needs to become an "else if(...".
> It used to be that all the other paths would return, so were mutually
> exclusive to this. Now they set a thing and keep going we need to
> avoid reading the register should there be a HPD gpio or the ddc probe
> succeeds.
> Memory says that otherwise Pi3 always reports connected.
>
> I fixed this in a downstream patch already -
> https://github.com/raspberrypi/linux/commit/d345caec1e9b2317b9cd7eb5b92ae453a0d3e98c
>
> Otherwise fine.
>
>   Dave
>
> > +               connected = true;
> > +       if (connected) {
> > +               if (connector->status != connector_status_connected) {
> > +                       struct edid *edid = drm_get_edid(connector, vc4_hdmi->ddc);
> > +
> > +                       if (edid) {
> > +                               cec_s_phys_addr_from_edid(vc4_hdmi->cec_adap, edid);
> > +                               vc4_hdmi->encoder.hdmi_monitor = drm_detect_hdmi_monitor(edid);
> > +                               drm_connector_update_edid_property(connector, edid);

Actually looking at this again in the context of the other changes, do
we need to call drm_connector_update_edid_property() here?

We've just called drm_get_edid() to get the edid, and that calls
drm_connector_update_edid_property() as well [1]
Updating vc4_hdmi->encoder.hdmi_monitor may be necessary. It's
otherwise done in vc4_hdmi_connector_get_modes, which I sort of expect
to be called almost immediately by the framework when connector_detect
returns "connected". I haven't checked if that is guaranteed though.

vc4_hdmi_connector_get_modes also includes a manual call to
drm_connector_update_edid_property after having just called
drm_get_edid, so that one feels redundant too.

  Dave

[1] https://elixir.bootlin.com/linux/v5.10/source/drivers/gpu/drm/drm_edid.c#L2059

> > +                               kfree(edid);
> > +                       }
> > +               }
> >                 return connector_status_connected;
> > +       }
> >         cec_phys_addr_invalidate(vc4_hdmi->cec_adap);
> >         return connector_status_disconnected;
> >  }
> > --
> > 2.28.0
> >