Hi Francesco, thanks for the patch.
Am Freitag, 17. Juli 2026, 14:18:44 CEST schrieb Francesco Dolcini: > From: Francesco Dolcini <[email protected]> > > LCDIF programs LCD_DATABUS_WIDTH from the selected media bus format. The > format reported by the downstream panel or bridge describes the display > input, but it does not describe how the LCDIF data pins are physically > wired on the board. > > These can differ. For example, a 16-bit LCDIF bus can be connected to a > 24-bit display by wiring the available color bits to the corresponding > display inputs. In that case, using the display's 24-bit format to > configure LCDIF selects the wrong data-bus mode and changes the assignment > of color bits on the LCD_DATA pins. > > Read the optional interface-pix-fmt property from the LCDIF node and use > it to select the media bus format used to configure LCDIF. This allows > the LCDIF bus mode to describe the physical interface independently of > the downstream display format. > > When the optional property is absent, continue using the format reported > by the downstream display device, preserving the existing behavior. > > This follows the same approach already implemented in > drivers/gpu/drm/imx/ipuv3/parallel-display.c. > > Signed-off-by: Francesco Dolcini <[email protected]> Nice, this work on my imx6ul based hardware where a 18-bit display is attached as a 24-bit one. Using interface-pix-fmt = "rgb24" this works as expected. Tested-by: Alexander Stein <[email protected]> > --- > drivers/gpu/drm/mxsfb/mxsfb_drv.c | 16 ++++++++++++++++ > drivers/gpu/drm/mxsfb/mxsfb_drv.h | 2 ++ > drivers/gpu/drm/mxsfb/mxsfb_kms.c | 8 ++++++++ > 3 files changed, 26 insertions(+) > > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c > b/drivers/gpu/drm/mxsfb/mxsfb_drv.c > index 9b8fbda85d28..edf347968fd2 100644 > --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c > +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c > @@ -12,7 +12,9 @@ > #include <linux/clk.h> > #include <linux/dma-mapping.h> > #include <linux/io.h> > +#include <linux/media-bus-format.h> > #include <linux/module.h> > +#include <linux/of.h> > #include <linux/platform_device.h> > #include <linux/property.h> > #include <linux/pm_runtime.h> > @@ -209,7 +211,10 @@ static int mxsfb_load(struct drm_device *drm, > const struct mxsfb_devdata *devdata) > { > struct platform_device *pdev = to_platform_device(drm->dev); > + struct device_node *np = pdev->dev.of_node; > struct mxsfb_drm_private *mxsfb; > + u32 bus_format = 0; > + const char *fmt; > int ret; > > mxsfb = devm_kzalloc(&pdev->dev, sizeof(*mxsfb), GFP_KERNEL); > @@ -236,6 +241,17 @@ static int mxsfb_load(struct drm_device *drm, > if (IS_ERR(mxsfb->clk_disp_axi)) > mxsfb->clk_disp_axi = NULL; > > + ret = of_property_read_string(np, "interface-pix-fmt", &fmt); > + if (!ret) { > + if (!strcmp(fmt, "rgb24")) > + bus_format = MEDIA_BUS_FMT_RGB888_1X24; > + else if (!strcmp(fmt, "rgb565")) > + bus_format = MEDIA_BUS_FMT_RGB565_1X16; > + else if (!strcmp(fmt, "rgb666")) > + bus_format = MEDIA_BUS_FMT_RGB666_1X18; > + } > + mxsfb->bus_format = bus_format; > + > ret = dma_set_mask_and_coherent(drm->dev, DMA_BIT_MASK(32)); > if (ret) > return ret; > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.h > b/drivers/gpu/drm/mxsfb/mxsfb_drv.h > index d160d921b25f..f64800f06a69 100644 > --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.h > +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.h > @@ -46,6 +46,8 @@ struct mxsfb_drm_private { > struct drm_connector *connector; > struct drm_bridge *bridge; > > + u32 bus_format; Indent broken. > + > bool crc_active; > }; > > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c > b/drivers/gpu/drm/mxsfb/mxsfb_kms.c > index d8ebebc5314b..8b482727aed5 100644 > --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c > +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c > @@ -386,6 +386,14 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc > *crtc, > if (!bus_format) > bus_format = MEDIA_BUS_FMT_RGB888_1X24; > > + /* > + * Prefer bus format set via optional "interface-pix-fmt" DT property, > + * over panel or next bridge bus format. This is necessary to support > + * 24bit DPI panels connected to a 18bit interface, for example. Maybe rephrase and state "mismatching interface" as it goes both ways. Best regards, Alexander > + */ > + if (mxsfb->bus_format) > + bus_format = mxsfb->bus_format; > + > mxsfb_crtc_mode_set_nofb(mxsfb, bridge_state, bus_format); > > /* Write cur_buf as well to avoid an initial corrupt frame */ > -- TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany Amtsgericht München, HRB 105018 Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider http://www.tq-group.com/
