linux-kernel - Re: [Nouveau] [PATCH v3 2/5] drm/nouveau/kms/nv50-: Explicitly check DPCD backlights for aux enable/brightness

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Message-ID: <CACO55tuMWVgsd44s1sAvgrKDHFZT2Z3F+CSqAh34_XaekYWuHA@mail.gmail.com>
Date:   Wed, 6 Oct 2021 18:30:07 +0200
From:   Karol Herbst <kherbst@...hat.com>
To:     Lyude Paul <lyude@...hat.com>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        nouveau <nouveau@...ts.freedesktop.org>,
        Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [Nouveau] [PATCH v3 2/5] drm/nouveau/kms/nv50-: Explicitly check
 DPCD backlights for aux enable/brightness

On Wed, Oct 6, 2021 at 4:41 AM Lyude Paul <lyude@...hat.com> wrote:
>
> Since we don't support hybrid AUX/PWM backlights in nouveau right now,
> let's add some explicit checks so that we don't break nouveau once we
> enable support for these backlights in other drivers.
>
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_backlight.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c
> index 1cbd71abc80a..ae2f2abc8f5a 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
> @@ -308,7 +308,10 @@ nv50_backlight_init(struct nouveau_backlight *bl,
>                 if (ret < 0)
>                         return ret;
>
> -               if (drm_edp_backlight_supported(edp_dpcd)) {
> +               /* TODO: Add support for hybrid PWM/DPCD panels */
> +               if (drm_edp_backlight_supported(edp_dpcd) &&
> +                   (edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&

where does the DP_EDP_BACKLIGHT_AUX_ENABLE_CAP come from? afaik
drm_edp_backlight_supported checks for
DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP and
DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP so wondering if this was
intentional or a typo

> +                   (edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) {
>                         NV_DEBUG(drm, "DPCD backlight controls supported on %s\n",
>                                  nv_conn->base.name);
>
> --
> 2.31.1
>