[PATCH] drm/imx: parallel-display: Prefer bus format set via legacy "interface-pix-fmt" DT property

[PATCH] drm/imx: parallel-display: Prefer bus format set via legacy "interface-pix-fmt" DT property

[Marek Vasut]

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>
---
Cc: David Airlie <airlied@gmail.com>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: dri-devel@lists.freedesktop.org
Cc: imx@lists.linux.dev
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/gpu/drm/imx/ipuv3/parallel-display.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/imx/ipuv3/parallel-display.c b/drivers/gpu/drm/imx/ipuv3/parallel-display.c
index 6fbf505d2801d..02bb38a1ee4eb 100644
--- 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;
 }
 
-- 
2.51.0

Re: [PATCH] drm/imx: parallel-display: Prefer bus format set via legacy "interface-pix-fmt" DT property

[Philipp Zabel]

On Sa, 2026-01-10 at 18:14 +0100, Marek Vasut wrote:
> 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>

regards
Philipp

Re: [PATCH] drm/imx: parallel-display: Prefer bus format set via legacy "interface-pix-fmt" DT property

[Marek Vasut]

On 1/13/26 12:31 PM, Philipp Zabel wrote:
> On Sa, 2026-01-10 at 18:14 +0100, Marek Vasut wrote:
>> 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>
If there are no objections, would it be OK to apply this ?

Re: [PATCH] drm/imx: parallel-display: Prefer bus format set via legacy "interface-pix-fmt" DT property

[Philipp Zabel]

On Sa, 2026-01-10 at 18:14 +0100, Marek Vasut wrote:
> 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>

Applied to drm-misc-next, thanks!

[1/1] drm/imx: parallel-display: Prefer bus format set via legacy "interface-pix-fmt" DT property
      commit: cdf26e1462c220629bb79d487263b66f8b679eab

regards
Philipp

Re: [PATCH] drm/imx: parallel-display: Prefer bus format set via legacy "interface-pix-fmt" DT property

[Marek Vasut]

On 3/13/26 4:33 PM, Philipp Zabel wrote:
> On Sa, 2026-01-10 at 18:14 +0100, Marek Vasut wrote:
>> 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>
> 
> Applied to drm-misc-next, thanks!
Thank you