Re: [PATCH v14 5/9] drm/bridge: dw-hdmi: repair interworking with hdmi-connector for jz4780

From: "H. Nikolaus Schaller" <hns@goldelico.com>
To: Paul Cercueil <paul@crapouillou.net>
Cc: Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Kees Cook <keescook@chromium.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Robert Foss <robert.foss@linaro.org>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Harry Wentland <harry.wentland@amd.com>,
	Sam Ravnborg <sam@ravnborg.org>,
	Maxime Ripard <maxime@cerno.tech>,
	Hans Verkuil <hverkuil-cisco@xs4all.nl>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>, Paul Boddie <paul@boddie.org.uk>,
	Andrzej Hajda <andrzej.hajda@intel.com>,
	Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
	devicetree@vger.kernel.org, linux-mips@vger.kernel.org,
	linux-kernel@vger.kernel.org, letux-kernel@openphoenux.org,
	Jonas Karlman <jonas@kwiboo.se>,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v14 5/9] drm/bridge: dw-hdmi: repair interworking with hdmi-connector for jz4780
Date: Sat, 12 Feb 2022 16:50:12 +0100	[thread overview]
Message-ID: <1AF73F85-8384-413C-8E2E-004E6DD75AAD@goldelico.com> (raw)
In-Reply-To: <7Y577R.WAL64FW8KJZJ1@crapouillou.net>

> Am 12.02.2022 um 16:06 schrieb Paul Cercueil <paul@crapouillou.net>:
> 
> Hi Nikolaus,
> 
> 
> Le sam., févr. 12 2022 at 15:19:23 +0100, H. Nikolaus Schaller <hns@goldelico.com> a écrit :
>> Commit 7cd70656d1285b ("drm/bridge: display-connector: implement bus fmts callbacks")
>> introduced a new mechanism to negotiate bus formats between hdmi connector
>> and the synopsys hdmi driver inside the jz4780.
>> By this, the dw-hdmi is no longer the only bridge and sets up a list
>> of formats in dw_hdmi_bridge_atomic_get_output_bus_fmts().
>> This includes MEDIA_BUS_FMT_UYVY8_1X16 which is chosen for the jz4780 but only
>> produces a black screen.
> 
> Neil pushed a fix yesterday that looks like it could fix your issue.
> The fix is: 1528038385c0 ("drm/bridge: dw-hdmi: use safe format when first in bridge chain")
> 
> Could you try if it does indeed fix your issue?

Sure.

Would have been nice and is a fix addressing same base commit, but is not a replacement for my attempt :(

Fortunately we can have both.

> 
> Cheers,
> -Paul
> 
>> This fix is based on the observation that max_bpc = 0 when running this
>> function while info->bpc = 8. Since the formats checks before this always test
>> for max_bpc >= info->pbc indirectly my assumption is that we must check it
>> here as well.
>> Adding the proposed patch makes the CI20/jz4780 panel work again in
>> MEDIA_BUS_FMT_RGB888_1X24 mode.
>> Fixes: 7cd70656d1285b ("drm/bridge: display-connector: implement bus fmts callbacks")
>> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
>> ---
>> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> index b0d8110dd412c..826a055a7a273 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> @@ -2620,10 +2620,10 @@ static u32 *dw_hdmi_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
>> 		output_fmts[i++] = MEDIA_BUS_FMT_RGB101010_1X30;
>> 	}
>> -	if (info->color_formats & DRM_COLOR_FORMAT_YCBCR422)
>> +	if (max_bpc >= info->bpc && info->color_formats & DRM_COLOR_FORMAT_YCBCR422)
>> 		output_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16;
>> -	if (info->color_formats & DRM_COLOR_FORMAT_YCBCR444)
>> +	if (max_bpc >= info->bpc && info->color_formats & DRM_COLOR_FORMAT_YCBCR444)
>> 		output_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
>> 	/* Default 8bit RGB fallback */
>> --
>> 2.33.0
> 
> 