linux-kernel - [PATCH v2 5/5] drm: mxsfb: Set proper default bus format when using a bridge

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Message-Id: <15afbcb04dea432867bb9f8b0e47205decd4bd6e.1633332399.git.agx@sigxcpu.org>
Date:   Mon,  4 Oct 2021 09:27:38 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Marek Vasut <marex@...x.de>,
        Stefan Agner <stefan@...er.ch>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Ondrej Jirman <megous@...ous.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v2 5/5] drm: mxsfb: Set proper default bus format when using a bridge

If a bridge doesn't do any bus format handling MEDIA_BUS_FMT_FIXED is
returned. Fallback to a reasonable default (MEDIA_BUS_FMT_RGB888_1X24) in
that case.

This unbreaks e.g. using mxsfb with the nwl bridge and mipi panels.

Fixes: b776b0f00f24 ("drm: mxsfb: Use bus_format from the nearest bridge if present")

Reported-by: Martin Kepplinger <martink@...teo.de>
Signed-off-by: Guido Günther <agx@...xcpu.org>
---
 drivers/gpu/drm/mxsfb/mxsfb_kms.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
index d6abd2077114..e3fbb8b58d5d 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
@@ -369,6 +369,12 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc *crtc,
 			drm_atomic_get_new_bridge_state(state,
 							mxsfb->bridge);
 		bus_format = bridge_state->input_bus_cfg.format;
+		if (bus_format == MEDIA_BUS_FMT_FIXED) {
+			dev_warn_once(drm->dev,
+				      "Bridge does not provide bus format, assuming MEDIA_BUS_FMT_RGB888_1X24.\n"
+				      "Please fix bridge driver by handling atomic_get_input_bus_fmts.\n");
+			bus_format = MEDIA_BUS_FMT_RGB888_1X24;
+		}
 	}
 
 	/* If there is no bridge, use bus format from connector */
-- 
2.33.0