Commit 4aebb790 authored by Noralf Trønnes's avatar Noralf Trønnes
Browse files

drm/mipi-dbi: Add support for DRM_FORMAT_RGB888 



DRM_FORMAT_RGB888 is 24 bits per pixel and it would be natural to send it
on the SPI bus using a 24 bits per word transfer. The problem with this
is that not all SPI controllers support 24 bpw.

Since DRM_FORMAT_RGB888 is stored in memory as little endian and the SPI
bus is big endian we use 8 bpw to always get the same pixel format on the
bus: b8g8r8.

The MIPI DCS specification lists the standard commands that can be sent
over the MIPI DBI interface. The set_address_mode (36h) command has one
bit in the parameter that controls RGB/BGR order. This means that the
controller can be configured to receive the pixel as BGR.

RGB888 is rarely supported on these controllers but RGB666 is very common.
All datasheets I have seen do at least support the pixel format option
where each color is sent as one byte and the 6 MSB's are used.

All this put together means that we can send each pixel as b8g8r8 and an
RGB666 capable controller sees this as b6x2g6x2r6x2.

v4:
- s/emulation_format/pixel_format/ (Dmitry)

Reviewed-by: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240604-panel-mipi-dbi-rgb666-v4-4-d7c2bcb9b78d@tronnes.org


Signed-off-by: default avatarNoralf Trønnes <noralf@tronnes.org>
parent df3fb27a

drivers/gpu/drm/drm_mipi_dbi.c

+25 −4
Original line number Diff line number Diff line
@@ -206,6 +206,7 @@ int mipi_dbi_buf_copy(void *dst, struct iosys_map *src, struct drm_framebuffer * 
		      struct drm_rect *clip, bool swap,

		      struct drm_format_conv_state *fmtcnv_state)

{

	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(fb->dev);

	struct drm_gem_object *gem = drm_gem_fb_get_obj(fb, 0);

	struct iosys_map dst_map = IOSYS_MAP_INIT_VADDR(dst);

	int ret;
@@ -222,9 +223,19 @@ int mipi_dbi_buf_copy(void *dst, struct iosys_map *src, struct drm_framebuffer * 
		else

			drm_fb_memcpy(&dst_map, NULL, src, fb, clip);

		break;

	case DRM_FORMAT_RGB888:

		drm_fb_memcpy(&dst_map, NULL, src, fb, clip);

		break;

	case DRM_FORMAT_XRGB8888:

		switch (dbidev->pixel_format) {

		case DRM_FORMAT_RGB565:

			drm_fb_xrgb8888_to_rgb565(&dst_map, NULL, src, fb, clip, fmtcnv_state, swap);

			break;

		case DRM_FORMAT_RGB888:

			drm_fb_xrgb8888_to_rgb888(&dst_map, NULL, src, fb, clip, fmtcnv_state);

			break;

		}

		break;

	default:

		drm_err_once(fb->dev, "Format is not supported: %p4cc\n",

			     &fb->format->format);
@@ -260,9 +271,11 @@ static void mipi_dbi_fb_dirty(struct iosys_map *src, struct drm_framebuffer *fb, 
	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(fb->dev);

	unsigned int height = rect->y2 - rect->y1;

	unsigned int width = rect->x2 - rect->x1;

	const struct drm_format_info *dst_format;

	struct mipi_dbi *dbi = &dbidev->dbi;

	bool swap = dbi->swap_bytes;

	int ret = 0;

	size_t len;

	bool full;

	void *tr;
@@ -283,8 +296,13 @@ static void mipi_dbi_fb_dirty(struct iosys_map *src, struct drm_framebuffer *fb, 
	mipi_dbi_set_window_address(dbidev, rect->x1, rect->x2 - 1, rect->y1,

				    rect->y2 - 1);



	ret = mipi_dbi_command_buf(dbi, MIPI_DCS_WRITE_MEMORY_START, tr,

				   width * height * 2);

	if (fb->format->format == DRM_FORMAT_XRGB8888)

		dst_format = drm_format_info(dbidev->pixel_format);

	else

		dst_format = fb->format;

	len = drm_format_info_min_pitch(dst_format, 0, width) * height;



	ret = mipi_dbi_command_buf(dbi, MIPI_DCS_WRITE_MEMORY_START, tr, len);

err_msg:

	if (ret)

		drm_err_once(fb->dev, "Failed to update display %d\n", ret);
@@ -572,7 +590,7 @@ static const uint32_t mipi_dbi_formats[] = { 
 * has one fixed &drm_display_mode which is rotated according to @rotation.

 * This mode is used to set the mode config min/max width/height properties.

 *

 * Use mipi_dbi_dev_init() if you don't need custom formats.

 * Use mipi_dbi_dev_init() if you want native RGB565 and emulated XRGB8888 format.

 *

 * Note:

 * Some of the helper functions expects RGB565 to be the default format and the
@@ -631,6 +649,9 @@ int mipi_dbi_dev_init_with_formats(struct mipi_dbi_dev *dbidev, 
	drm->mode_config.min_height = dbidev->mode.vdisplay;

	drm->mode_config.max_height = dbidev->mode.vdisplay;

	dbidev->rotation = rotation;

	dbidev->pixel_format = formats[0];

	if (formats[0] == DRM_FORMAT_RGB888)

		dbidev->dbi.write_memory_bpw = 8;



	DRM_DEBUG_KMS("rotation = %u\n", rotation);

include/drm/drm_mipi_dbi.h

+5 −0
Original line number Diff line number Diff line
@@ -101,6 +101,11 @@ struct mipi_dbi_dev { 
	 */

	struct drm_display_mode mode;



	/**

	 * @pixel_format: Native pixel format (DRM_FORMAT\_\*)

	 */

	u32 pixel_format;



	/**

	 * @tx_buf: Buffer used for transfer (copy clip rect area)

	 */