[PATCH] drm/imx: parallel-display: Adjust bus_flags and bus_format handling

[Marek Vasut]

The bus_flags and bus_format handling logic does not seem to cover
all potential usecases. Specifically, this seems to fail with an
"edt,etm0700g0edh6" display attached to an 24bit display interface,
with interface-pix-fmt = "rgb24" set in DT.

In this specific setup, the panel-simple.c driver entry for the display
sets .bus_flags to non-zero value. However, as imxpd->bus_format is set
from the DT property "interface-pix-fmt", imx_pd_encoder_atomic_check()
will set imx_crtc_state->bus_flags = imxpd->bus_flags even though the
imxpd->bus_flags is zero, while the di->bus_flags is correctly set by
the panel-simple.c and non-zero. The result is incorrect flags being
used for the display configuration and thus an image corruption.
(Specifically, DRM_BUS_FLAG_PIXDATA_POSEDGE is not propagated and thus
the ipuv3 clocks pixels on the wrong edge).

This patch fixes the problem by overriding the imx_crtc_state->bus_format
from the imxpd->bus_format only if the DT property "interface-pix-fmt" is
present or if the DI provides no formats. Similarly for bus_flags, which
are set from imxpd->bus_flags only if the DI provides no formats.

Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: David Airlie <airlied at linux.ie>
Cc: Fabio Estevam <festevam at gmail.com>
Cc: NXP Linux Team <linux-imx at nxp.com>
Cc: Philipp Zabel <p.zabel at pengutronix.de>
Cc: Sascha Hauer <s.hauer at pengutronix.de>
Cc: Shawn Guo <shawnguo at kernel.org>
Cc: linux-arm-kernel at lists.infradead.org
To: dri-devel at lists.freedesktop.org
---
 drivers/gpu/drm/imx/parallel-display.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/imx/parallel-display.c b/drivers/gpu/drm/imx/parallel-display.c
index 35518e5de356..92f00b12c068 100644
--- a/drivers/gpu/drm/imx/parallel-display.c
+++ b/drivers/gpu/drm/imx/parallel-display.c
@@ -113,13 +113,16 @@ static int imx_pd_encoder_atomic_check(struct drm_encoder *encoder,
 	struct drm_display_info *di = &conn_state->connector->display_info;
 	struct imx_parallel_display *imxpd = enc_to_imxpd(encoder);
 
-	if (!imxpd->bus_format && di->num_bus_formats) {
-		imx_crtc_state->bus_flags = di->bus_flags;
+	if (imxpd->bus_format || !di->num_bus_formats)
+		imx_crtc_state->bus_format = imxpd->bus_format;
+	else
 		imx_crtc_state->bus_format = di->bus_formats[0];
-	} else {
+
+	if (di->num_bus_formats)
+		imx_crtc_state->bus_flags = di->bus_flags;
+	else
 		imx_crtc_state->bus_flags = imxpd->bus_flags;
-		imx_crtc_state->bus_format = imxpd->bus_format;
-	}
+
 	imx_crtc_state->di_hsync_pin = 2;
 	imx_crtc_state->di_vsync_pin = 3;
 
-- 
2.24.0.rc1