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drm/mipi-dbi: Add support for DRM_FORMAT_RGB888

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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: Dmitry 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: Noralf Trønnes <noralf@tronnes.org>
This commit is contained in:
Noralf Trønnes 2024-06-04 15:20:31 +02:00
parent df3fb27a74
commit 4aebb79021
2 changed files with 30 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
drivers/gpu/drm/drm_mipi_dbi.c
View File

@ -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;
@ -222,8 +223,18 @@ 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:
drm_fb_xrgb8888_to_rgb565(&dst_map, NULL, src, fb, clip, fmtcnv_state, swap);
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",
@ -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);

5
include/drm/drm_mipi_dbi.h
View File

@ -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)
*/