linux-kernel - Re: [PATCH v2 3/9] drm/bridge: ite-it6263: handle unsupported InfoFrames

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Message-ID: <y3sndmfnwtljkbrssyycg6scjujt4kkjfo3gjclo3suzvqdahl@bdrdzmiolcb4>
Date: Mon, 29 Sep 2025 11:58:26 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Liu Ying <victor.liu@....com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        Andy Yan <andy.yan@...k-chips.com>,
        Samuel Holland <samuel@...lland.org>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH v2 3/9] drm/bridge: ite-it6263: handle unsupported
 InfoFrames

On Mon, Sep 29, 2025 at 03:56:31PM +0800, Liu Ying wrote:
> On 09/28/2025, Dmitry Baryshkov wrote:
> > Make hdmi_write_hdmi_infoframe() and hdmi_clear_infoframe() callbacks
> > return -EOPNOTSUPP for unsupported InfoFrames and make sure that
> > atomic_check() callback doesn't allow unsupported InfoFrames to be
> > enabled.
> > 
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> > ---
> >  drivers/gpu/drm/bridge/ite-it6263.c | 27 +++++++++++++++++++++++++--
> >  1 file changed, 25 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/ite-it6263.c b/drivers/gpu/drm/bridge/ite-it6263.c
> > index 2eb8fba7016cbf0dcb19aec4ca8849f1fffaa64c..cf3d76d748dde51e93b2b19cc2cbe023ca2629b8 100644
> > --- a/drivers/gpu/drm/bridge/ite-it6263.c
> > +++ b/drivers/gpu/drm/bridge/ite-it6263.c
> > @@ -26,6 +26,7 @@
> >  #include <drm/drm_crtc.h>
> >  #include <drm/drm_edid.h>
> >  #include <drm/drm_of.h>
> > +#include <drm/drm_print.h>
> >  #include <drm/drm_probe_helper.h>
> >  
> >  /* -----------------------------------------------------------------------------
> > @@ -772,7 +773,7 @@ static int it6263_hdmi_clear_infoframe(struct drm_bridge *bridge,
> >  		regmap_write(it->hdmi_regmap, HDMI_REG_PKT_NULL_CTRL, 0);
> >  		break;
> >  	default:
> > -		dev_dbg(it->dev, "unsupported HDMI infoframe 0x%x\n", type);
> > +		return -EOPNOTSUPP;
> >  	}
> >  
> >  	return 0;
> > @@ -812,13 +813,35 @@ static int it6263_hdmi_write_infoframe(struct drm_bridge *bridge,
> >  			     ENABLE_PKT | REPEAT_PKT);
> >  		break;
> >  	default:
> > -		dev_dbg(it->dev, "unsupported HDMI infoframe 0x%x\n", type);
> > +		return -EOPNOTSUPP;
> >  	}
> >  
> >  	return 0;
> >  }
> >  
> > +static int it6263_bridge_atomic_check(struct drm_bridge *bridge,
> > +				      struct drm_bridge_state *bridge_state,
> > +				      struct drm_crtc_state *crtc_state,
> > +				      struct drm_connector_state *conn_state)
> > +{
> > +	/* not supported by the driver */
> > +	conn_state->hdmi.infoframes.spd.set = false;
> > +
> > +	/* should not happen, audio support not enabled */
> > +	if (drm_WARN_ON_ONCE(bridge->encoder->dev,
> > +			     conn_state->connector->hdmi.infoframes.audio.set))
> 
> Maybe use drm_err_once() instead to provide the reason for the warning in
> a string?

I can change all of them to drm_err_once(), sure.

> 
> > +		return -EOPNOTSUPP;
> 
> As this check could return error, it should be moved before
> 'conn_state->hdmi.infoframes.spd.set = false;' to gain a little performance.

I'd say, it would be negligible.

> 
> > +
> > +	/* should not happen, HDR support not enabled */
> > +	if (drm_WARN_ON_ONCE(bridge->encoder->dev,
> > +			     conn_state->hdmi.infoframes.hdr_drm.set))
> > +		return -EOPNOTSUPP;
> 
> I don't think IT6263 chip supports DRM infoframe.  The drm_WARN_ON_ONCE()
> call could make driver readers think that DRM infoframe could be enabled
> in the future as audio infoframe has the same warning and IT6263 chip does
> support audio infoframe.  So, maybe:
> 
> /* IT6263 chip doesn't support DRM infoframe. */
> conn_state->hdmi.infoframes.hdr_drm.set = false;

I'd rather not do that. My point here was that the driver can not end up
in the state where this frame is enabled, because it can only happen if
the driver sets max_bpc (which it doesn't). Likewise Audio InfoFrame can
not get enabled because the driver doesn't call into audio functions. On
the contrary, SPD frame (or HDMI in several other drivers) can be
enabled by the framework, so we silently turn then off here.

> 
> > +
> > +	return 0;
> > +}
> > +
> >  static const struct drm_bridge_funcs it6263_bridge_funcs = {
> > +	.atomic_check = it6263_bridge_atomic_check,
> >  	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
> >  	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
> >  	.atomic_reset = drm_atomic_helper_bridge_reset,
> > 
> 
> 
> -- 
> Regards,
> Liu Ying

-- 
With best wishes
Dmitry