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From:   "H. Nikolaus Schaller" <hns@goldelico.com>
To:     Paul Cercueil <paul@crapouillou.net>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
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Cc:     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: [PATCH v12 6/9] dw-hdmi/ingenic-dw-hdmi: repair interworking with hdmi-connector
Date:   Mon, 31 Jan 2022 13:26:52 +0100
Message-Id: <d0633be0eb6b96a43aa8e3dd6af3241437a8111d.1643632014.git.hns@goldelico.com>
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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@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 52e7cd2e020d3..34703a15ee4ff 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_YCRCB422)
+	if (max_bpc >= info->bpc && info->color_formats & DRM_COLOR_FORMAT_YCRCB422)
 		output_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16;
 
-	if (info->color_formats & DRM_COLOR_FORMAT_YCRCB444)
+	if (max_bpc >= info->bpc && info->color_formats & DRM_COLOR_FORMAT_YCRCB444)
 		output_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
 
 	/* Default 8bit RGB fallback */
-- 
2.33.0