linux-kernel - Re: [RFC v2 1/8] drm/i915/dp: Program source OUI on eDP panels

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Date:   Fri, 16 Oct 2020 16:13:00 -0700
From:   Vasily Khoruzhick <anarsoul@...il.com>
To:     Lyude Paul <lyude@...hat.com>
Cc:     intel-gfx@...ts.freedesktop.org,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Ville Syrjala <ville.syrjala@...ux.intel.com>,
        thaytan@...aisin.net,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        José Roberto de Souza <jose.souza@...el.com>,
        Manasi Navare <manasi.d.navare@...el.com>,
        Uma Shankar <uma.shankar@...el.com>,
        Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Wambui Karuga <wambui.karugax@...il.com>,
        Sean Paul <seanpaul@...omium.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2 1/8] drm/i915/dp: Program source OUI on eDP panels

On Wed, Sep 16, 2020 at 10:19 AM Lyude Paul <lyude@...hat.com> wrote:
>
> Since we're about to start adding support for Intel's magic HDR
> backlight interface over DPCD, we need to ensure we're properly
> programming this field so that Intel specific sink services are exposed.
> Otherwise, 0x300-0x3ff will just read zeroes.
>
> We also take care not to reprogram the source OUI if it already matches
> what we expect. This is just to be careful so that we don't accidentally
> take the panel out of any backlight control modes we found it in.
>
> v2:
> * Add careful parameter to intel_edp_init_source_oui() to avoid
>   re-writing the source OUI if it's already been set during driver
>   initialization
>
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> Cc: thaytan@...aisin.net
> Cc: Vasily Khoruzhick <anarsoul@...il.com>

Hi Lyude,

Sorry for a late reply.

Whole series is:

Tested-by: Vasily Khoruzhick <anarsoul@...il.com>

Regards,
Vasily

> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 33 +++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 4bd10456ad188..7db2b6a3cd52e 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -3424,6 +3424,29 @@ void intel_dp_sink_set_decompression_state(struct intel_dp *intel_dp,
>                             enable ? "enable" : "disable");
>  }
>
> +static void
> +intel_edp_init_source_oui(struct intel_dp *intel_dp, bool careful)
> +{
> +       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> +       u8 oui[] = { 0x00, 0xaa, 0x01 };
> +       u8 buf[3] = { 0 };
> +
> +       /*
> +        * During driver init, we want to be careful and avoid changing the source OUI if it's
> +        * already set to what we want, so as to avoid clearing any state by accident
> +        */
> +       if (careful) {
> +               if (drm_dp_dpcd_read(&intel_dp->aux, DP_SOURCE_OUI, buf, sizeof(buf)) < 0)
> +                       drm_err(&i915->drm, "Failed to read source OUI\n");
> +
> +               if (memcmp(oui, buf, sizeof(oui)) == 0)
> +                       return;
> +       }
> +
> +       if (drm_dp_dpcd_write(&intel_dp->aux, DP_SOURCE_OUI, oui, sizeof(oui)) < 0)
> +               drm_err(&i915->drm, "Failed to write source OUI\n");
> +}
> +
>  /* If the sink supports it, try to set the power state appropriately */
>  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode)
>  {
> @@ -3443,6 +3466,10 @@ void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode)
>         } else {
>                 struct intel_lspcon *lspcon = dp_to_lspcon(intel_dp);
>
> +               /* Write the source OUI as early as possible */
> +               if (intel_dp_is_edp(intel_dp))
> +                       intel_edp_init_source_oui(intel_dp, false);
> +
>                 /*
>                  * When turning on, we need to retry for 1ms to give the sink
>                  * time to wake up.
> @@ -4607,6 +4634,12 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
>         if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv))
>                 intel_dp_get_dsc_sink_cap(intel_dp);
>
> +       /*
> +        * If needed, program our source OUI so we can make various Intel-specific AUX services
> +        * available (such as HDR backlight controls)
> +        */
> +       intel_edp_init_source_oui(intel_dp, true);
> +
>         return true;
>  }
>
> --
> 2.26.2
>