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Message-Id: <20240512-panel-mipi-dbi-rgb666-v2-4-49dd266328a0@tronnes.org>
Date: Sun, 12 May 2024 17:25:41 +0200
From: Noralf Trønnes via B4 Relay <devnull+noralf.tronnes.org@...nel.org>
To: Neil Armstrong <neil.armstrong@...aro.org>,
Jessica Zhang <quic_jesszhan@...cinc.com>, Sam Ravnborg <sam@...nborg.org>,
David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org,
Kamlesh Gurudasani <kamlesh.gurudasani@...il.com>,
Tommaso Merciai <tommaso.merciai@...rulasolutions.com>,
Noralf Trønnes <noralf@...nnes.org>
Subject: [PATCH v2 4/5] drm/mipi-dbi: Add support for DRM_FORMAT_RGB888
From: Noralf Trønnes <noralf@...nnes.org>
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.
Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
---
drivers/gpu/drm/drm_mipi_dbi.c | 29 +++++++++++++++++++++++++----
include/drm/drm_mipi_dbi.h | 5 +++++
2 files changed, 30 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
index 77f8a828d6e0..eb330676857c 100644
--- a/drivers/gpu/drm/drm_mipi_dbi.c
+++ b/drivers/gpu/drm/drm_mipi_dbi.c
@@ -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->emulation_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->emulation_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->emulation_format = formats[0];
+ if (formats[0] == DRM_FORMAT_RGB888)
+ dbidev->dbi.write_memory_bpw = 8;
DRM_DEBUG_KMS("rotation = %u\n", rotation);
diff --git a/include/drm/drm_mipi_dbi.h b/include/drm/drm_mipi_dbi.h
index b36596efdcc3..85bf19b98cee 100644
--- a/include/drm/drm_mipi_dbi.h
+++ b/include/drm/drm_mipi_dbi.h
@@ -101,6 +101,11 @@ struct mipi_dbi_dev {
*/
struct drm_display_mode mode;
+ /**
+ * @emulation_format: Pixel format to use when emulating XRGB8888
+ */
+ u32 emulation_format;
+
/**
* @tx_buf: Buffer used for transfer (copy clip rect area)
*/
--
2.45.0
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