linux-kernel - Re: [PATCH v3 3/4] drm/bridge: ti-sn65dsi86: Read EDID blob over DDC

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Message-ID: <161646947526.2972785.6883720652669260316@swboyd.mtv.corp.google.com>
Date:   Mon, 22 Mar 2021 20:17:55 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Jonas Karlman <jonas@...boo.se>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Douglas Anderson <dianders@...omium.org>,
        Sean Paul <seanpaul@...omium.org>
Subject: Re: [PATCH v3 3/4] drm/bridge: ti-sn65dsi86: Read EDID blob over DDC

Quoting Laurent Pinchart (2021-03-17 17:20:43)
> Hi Stephen,
> 
> Reviving a bit of an old thread, for a question.
> 
> On Mon, Nov 02, 2020 at 10:11:43AM -0800, Stephen Boyd wrote:
> > @@ -265,6 +267,23 @@ connector_to_ti_sn_bridge(struct drm_connector *connector)
> >  static int ti_sn_bridge_connector_get_modes(struct drm_connector *connector)
> >  {
> >       struct ti_sn_bridge *pdata = connector_to_ti_sn_bridge(connector);
> > +     struct edid *edid = pdata->edid;
> > +     int num, ret;
> > +
> > +     if (!edid) {
> > +             pm_runtime_get_sync(pdata->dev);
> > +             edid = pdata->edid = drm_get_edid(connector, &pdata->aux.ddc);
> > +             pm_runtime_put(pdata->dev);
> 
> Is there any specific reason to use the indirect access method, compared
> to the direct method that translates access to an I2C ancillary address
> to an I2C-over-AUX transaction (see page 20 of SLLSEH2B) ? The direct
> method seems it would be more efficient.
> 

No I don't think it matters. I was just using the existing support code
that Sean wrote instead of digging into the details. Maybe Sean ran into
something earlier and abandoned that approach?