linux-kernel - [PATCH v15 4/7] drm/bridge: dw-hdmi: repair interworking with hdmi-connector for jz4780

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Message-Id: <d4d08582c49ec089095dd0ede4cdf2752f9d1eb8.1644681054.git.hns@goldelico.com>
Date:   Sat, 12 Feb 2022 16:50:52 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Paul Boddie <paul@...die.org.uk>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Paul Cercueil <paul@...pouillou.net>,
        Maxime Ripard <maxime@...no.tech>,
        Harry Wentland <harry.wentland@....com>,
        "H. Nikolaus Schaller" <hns@...delico.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
Cc:     Jonas Karlman <jonas@...boo.se>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-mips@...r.kernel.org,
        letux-kernel@...nphoenux.org
Subject: [PATCH v15 4/7] drm/bridge: dw-hdmi: repair interworking with hdmi-connector for jz4780

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.

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@...delico.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