Hi Francesco,
On 26-08-12, Francesco Dolcini wrote:
> 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 bus-width endpoint property from the LCDIF output port
> 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, or it has an invalid value, continue
> using the format reported by the downstream display device, preserving
> the existing behavior. The code is not validating the DT for
> correctness and just fall back to the previous behavior in case of
> errors.
>
> Signed-off-by: Francesco Dolcini <[email protected]>
> ---
> v3: improve commit message and make it clear that the code assumes that
> the DT is correct, when the DT contains an invalid property value,
> the code safely fall-back to the previous behavior
> v2: use the common bus-width property instead of the legacy interface-pix-fmt
> ---
> drivers/gpu/drm/mxsfb/mxsfb_drv.c | 24 ++++++++++++++++++++++++
> drivers/gpu/drm/mxsfb/mxsfb_drv.h | 2 ++
> drivers/gpu/drm/mxsfb/mxsfb_kms.c | 12 ++++++++++++
> 3 files changed, 38 insertions(+)
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> index 8b4a500347fb..f8ecc8bbd63c 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> @@ -12,7 +12,10 @@
> #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/of_graph.h>
> #include <linux/platform_device.h>
> #include <linux/property.h>
> #include <linux/pm_runtime.h>
> @@ -211,7 +214,10 @@ 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;
> + struct device_node *ep;
> + u32 bus_width = 0;
IMHO this default value makes no sense with..
> int ret;
>
> mxsfb = devm_kzalloc(&pdev->dev, sizeof(*mxsfb), GFP_KERNEL);
> @@ -238,6 +244,24 @@ static int mxsfb_load(struct drm_device *drm,
> if (IS_ERR(mxsfb->clk_disp_axi))
> mxsfb->clk_disp_axi = NULL;
>
> + ep = of_graph_get_next_endpoint(np, NULL);
> + if (ep) {
> + of_property_read_u32(ep, "bus-width", &bus_width);
> + of_node_put(ep);
> + }
> +
> + switch (bus_width) {
> + case 16:
> + mxsfb->bus_format = MEDIA_BUS_FMT_RGB565_1X16;
> + break;
> + case 18:
> + mxsfb->bus_format = MEDIA_BUS_FMT_RGB666_1X18;
> + break;
> + case 24:
> + mxsfb->bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> + break;
these cases in case no bus-width was specified without the knowledge of
the mxsfb_kms.c since the '0' value is not covered. However, I'm not the
maintainer of this driver. Thanks for making use of the bus-width
property :)
Regards,
Marco
> + }
> +
> 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..bdc47ce5be79 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;
> +
> bool crc_active;
> };
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> index d8ebebc5314b..1d78c486d147 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> @@ -386,6 +386,18 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc
> *crtc,
> if (!bus_format)
> bus_format = MEDIA_BUS_FMT_RGB888_1X24;
>
> + /*
> + * Prefer the bus format derived from the OF graph endpoint "bus-width"
> + * property when available. Otherwise, use the bus format reported by
> + * the downstream bridge or panel.
> + *
> + * This supports mismatched display and interface bus widths, such as
> + * a 24-bit panel connected through an 18-bit interface or an 18-bit
> + * panel connected through a 24-bit interface.
> + */
> + 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 */
> --
> 2.47.3
>
>
>
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