On 12/14/2016 02:02 AM, Stefan Agner wrote:
> The LCD bus width does not need to align with the pixel format. The
> LCDIF controller automatically converts between pixel formats and
> bus width by padding or dropping LSBs.
>
> The DRM subsystem has the notion of bus_format which allows to
> determine what bus_formats are supported by the display. Choose the
> first available or fallback to 24 bit if none are available.
>
> Signed-off-by: Stefan Agner <ste...@agner.ch>
Minor nits below.
> ---
> Changes in v2:
> - Use seperate function mxsfb_set_bus_fmt
>
> drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 33 +++++++++++++++++++++++++++++++--
> drivers/gpu/drm/mxsfb/mxsfb_regs.h | 1 +
> 2 files changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> index 4bcc8a3..956769b 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> @@ -65,13 +65,11 @@ static int mxsfb_set_pixel_fmt(struct mxsfb_drm_private
> *mxsfb)
> switch (format) {
> case DRM_FORMAT_RGB565:
> dev_dbg(drm->dev, "Setting up RGB565 mode\n");
> - ctrl |= CTRL_SET_BUS_WIDTH(STMLCDIF_16BIT);
> ctrl |= CTRL_SET_WORD_LENGTH(0);
> ctrl1 |= CTRL1_SET_BYTE_PACKAGING(0xf);
> break;
> case DRM_FORMAT_XRGB8888:
> dev_dbg(drm->dev, "Setting up XRGB8888 mode\n");
> - ctrl |= CTRL_SET_BUS_WIDTH(STMLCDIF_24BIT);
> ctrl |= CTRL_SET_WORD_LENGTH(3);
> /* Do not use packed pixels = one pixel per word instead. */
> ctrl1 |= CTRL1_SET_BYTE_PACKAGING(0x7);
> @@ -87,6 +85,35 @@ static int mxsfb_set_pixel_fmt(struct mxsfb_drm_private
> *mxsfb)
> return 0;
> }
>
> +static void mxsfb_set_bus_fmt(struct mxsfb_drm_private *mxsfb)
> +{
> + struct drm_crtc *crtc = &mxsfb->pipe.crtc;
> + struct drm_device *drm = crtc->dev;
> + u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> + u32 reg;
^^^ this is uninitialized
> + writel(CTRL_BUS_WIDTH_MASK, mxsfb->base + LCDC_CTRL + REG_CLR);
> +
> + if (mxsfb->connector.display_info.num_bus_formats)
> + bus_format = mxsfb->connector.display_info.bus_formats[0];
> +
> + switch (bus_format) {
> + case MEDIA_BUS_FMT_RGB565_1X16:
> + reg |= CTRL_SET_BUS_WIDTH(STMLCDIF_16BIT);
^^^
here you're doing operation on uninited value.
> + break;
> + case MEDIA_BUS_FMT_RGB666_1X18:
> + reg |= CTRL_SET_BUS_WIDTH(STMLCDIF_18BIT);
> + break;
> + case MEDIA_BUS_FMT_RGB888_1X24:
> + reg |= CTRL_SET_BUS_WIDTH(STMLCDIF_24BIT);
> + break;
> + default:
> + dev_err(drm->dev, "Unknown media bus format %d\n", bus_format);
> + break;
> + }
> + writel(reg, mxsfb->base + LCDC_CTRL + REG_SET);
What I was thinking might be better is to save the calculated LCD_CRTC
value in mxsfb_drm_private , but maybe R-M-W is good enough after all?
Two writes are IMO not great because it unnecessarily reconfigures the
controller twice.
> +}
> +
> static void mxsfb_enable_controller(struct mxsfb_drm_private *mxsfb)
> {
> u32 reg;
> @@ -182,6 +209,8 @@ static void mxsfb_crtc_mode_set_nofb(struct
> mxsfb_drm_private *mxsfb)
>
> writel(vdctrl0, mxsfb->base + LCDC_VDCTRL0);
>
> + mxsfb_set_bus_fmt(mxsfb);
> +
> /* Frame length in lines. */
> writel(m->crtc_vtotal, mxsfb->base + LCDC_VDCTRL1);
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_regs.h
> b/drivers/gpu/drm/mxsfb/mxsfb_regs.h
> index 31d62cd..66a6ba9 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_regs.h
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_regs.h
> @@ -44,6 +44,7 @@
> #define CTRL_DATA_SELECT (1 << 16)
> #define CTRL_SET_BUS_WIDTH(x) (((x) & 0x3) << 10)
> #define CTRL_GET_BUS_WIDTH(x) (((x) >> 10) & 0x3)
> +#define CTRL_BUS_WIDTH_MASK (0x3 << 10)
> #define CTRL_SET_WORD_LENGTH(x) (((x) & 0x3) << 8)
> #define CTRL_GET_WORD_LENGTH(x) (((x) >> 8) & 0x3)
> #define CTRL_MASTER (1 << 5)
>
--
Best regards,
Marek Vasut
