drm/imx: parallel-display: Prefer bus format set via legacy "interface-pix-fmt" DT...

Prefer bus format set via legacy "interface-pix-fmt" DT property
over panel bus format. This is necessary to retain support for
DTs which configure the IPUv3 parallel output as 24bit DPI, but
connect 18bit DPI panels to it with hardware swizzling.

This used to work up to Linux 6.12, but stopped working in 6.13,
reinstate the behavior to support old DTs.

Cc: stable@vger.kernel.org
Fixes: 5f6e56d3319d ("drm/imx: parallel-display: switch to drm_panel_bridge")
Signed-off-by: Marek Vasut <marex@nabladev.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://patch.msgid.link/20260110171510.692666-1-marex@nabladev.com

diff --git a/drivers/gpu/drm/imx/ipuv3/parallel-display.c b/drivers/gpu/drm/imx/ipuv3/parallel-display.c
index 4ce772bc3cb3a122379290fd8f7b5b88f08f16c8..a356f0b764cb79bd6efd103d2f3c9fddf99b9a34 100644 (file)
--- a/drivers/gpu/drm/imx/ipuv3/parallel-display.c
+++ b/drivers/gpu/drm/imx/ipuv3/parallel-display.c
@@ -110,8 +110,7 @@ imx_pd_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
                output_fmt = imxpd->bus_format ? : MEDIA_BUS_FMT_RGB888_1X24;
 
        /* Now make sure the requested output format is supported. */
-       if ((imxpd->bus_format && imxpd->bus_format != output_fmt) ||
-           !imx_pd_format_supported(output_fmt)) {
+       if (!imx_pd_format_supported(output_fmt)) {
                *num_input_fmts = 0;
                return NULL;
        }
@@ -121,7 +120,17 @@ imx_pd_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
        if (!input_fmts)
                return NULL;
 
-       input_fmts[0] = output_fmt;
+       /*
+        * Prefer bus format set via legacy "interface-pix-fmt" DT property
+        * over panel bus format. This is necessary to retain support for
+        * DTs which configure the IPUv3 parallel output as 24bit, but
+        * connect 18bit DPI panels to it with hardware swizzling.
+        */
+       if (imxpd->bus_format && imxpd->bus_format != output_fmt)
+               input_fmts[0] = imxpd->bus_format;
+       else
+               input_fmts[0] = output_fmt;
+
        return input_fmts;
 }