[PATCH v5 2/6] drm/ssd130x: Change SSD133X color format to RGB565 from RGB332

[Amit Barzilai <amit.barzilai22@gmail.com>]

SSD133X screens were driven at 8bpp RGB332 despite supporting 16bpp RGB565.
Switch the SSD133X data path to RGB565.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Amit Barzilai <amit.barzilai22@gmail.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
---
 drivers/gpu/drm/solomon/ssd130x.c | 48 ++++++++++++++++++++-----------
 1 file changed, 31 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/solomon/ssd130x.c b/drivers/gpu/drm/solomon/ssd130x.c
index 0b0fc6fe3df2..8cf1e9c84a81 100644
--- a/drivers/gpu/drm/solomon/ssd130x.c
+++ b/drivers/gpu/drm/solomon/ssd130x.c
@@ -146,6 +146,11 @@
 #define SSD133X_DEFAULT_CONTRAST_B		0x50
 #define SSD133X_DEFAULT_CONTRAST_C		0x7d
 
+/* ssd133x remap byte (data of SSD13XX_SET_SEG_REMAP) */
+#define SSD133X_SET_REMAP_COM_SPLIT		BIT(5)
+#define SSD133X_SET_REMAP_COLOR_DEPTH_MASK	GENMASK(7, 6)
+#define SSD133X_COLOR_DEPTH_65K			0x1
+
 #define MAX_CONTRAST 255
 
 const struct ssd130x_deviceinfo ssd130x_variants[] = {
@@ -618,17 +623,17 @@ static int ssd133x_set_contrast(struct ssd130x_device *ssd130x, u32 brightness)
 static int ssd133x_init(struct ssd130x_device *ssd130x)
 {
 	int ret;
+	/*
+	 * Horizontal address increment, normal SA,SB,SC (e.g. RGB) sub-pixel
+	 * order, COM split odd even and 65k (RGB565) color depth.
+	 */
+	const u8 remap = SSD133X_SET_REMAP_COM_SPLIT |
+			 FIELD_PREP(SSD133X_SET_REMAP_COLOR_DEPTH_MASK, SSD133X_COLOR_DEPTH_65K);
 	const u8 cmds[] = {
 		2, SSD133X_SET_MASTER_CURRENT, 0x06,
 		3, SSD133X_SET_COL_RANGE, 0x00, ssd130x->width - 1,
 		3, SSD133X_SET_ROW_RANGE, 0x00, ssd130x->height - 1,
-		/*
-		 * Horizontal Address Increment
-		 * Normal order SA,SB,SC (e.g. RGB)
-		 * COM Split Odd Even
-		 * 256 color format
-		 */
-		2, SSD13XX_SET_SEG_REMAP, 0x20,
+		2, SSD13XX_SET_SEG_REMAP, remap,
 		2, SSD133X_SET_DISPLAY_START, 0x00,
 		2, SSD133X_SET_DISPLAY_OFFSET, 0x00,
 		1, SSD133X_SET_DISPLAY_NORMAL,
@@ -829,14 +834,20 @@ static int ssd133x_update_rect(struct ssd130x_device *ssd130x,
 	 * COM0 to COM[N - 1] are the rows and SEG0 to SEG[M - 1] are
 	 * the columns.
 	 *
-	 * Each Segment has a 8-bit pixel and each Common output has a
-	 * row of pixels. When using the (default) horizontal address
-	 * increment mode, each byte of data sent to the controller has
-	 * a Segment (e.g: SEG0).
+	 * Each Segment holds one pixel and each Common output has a row
+	 * of pixels. A pixel is 8 bits (one byte) in the 256 color
+	 * (RGB332) format or 16 bits (two bytes) in the 65k color
+	 * (RGB565) format. When using the (default) horizontal address
+	 * increment mode, the pixel data is sent Segment by Segment
+	 * (e.g: SEG0 first).
 	 *
 	 * When using the 256 color depth format, each pixel contains 3
-	 * sub-pixels for color A, B and C. These have 3 bit, 3 bit and
-	 * 2 bits respectively.
+	 * sub-pixels for color A, B and C. These have 3, 3 and 2 bits
+	 * respectively.
+	 *
+	 * When using the 65k color depth format, each pixel contains 3
+	 * sub-pixels for color A, B and C. These have 5, 6 and 5 bits
+	 * respectively.
 	 */
 
 	/* Set column start and end */
@@ -909,9 +920,10 @@ static void ssd132x_clear_screen(struct ssd130x_device *ssd130x, u8 *data_array)
 
 static void ssd133x_clear_screen(struct ssd130x_device *ssd130x, u8 *data_array)
 {
-	const struct drm_format_info *fi = drm_format_info(DRM_FORMAT_RGB332);
+	const struct drm_format_info *fi;
 	unsigned int pitch;
 
+	fi = drm_format_info(DRM_FORMAT_RGB565);
 	if (!fi)
 		return;
 
@@ -978,17 +990,18 @@ static int ssd133x_fb_blit_rect(struct drm_framebuffer *fb,
 				struct drm_format_conv_state *fmtcnv_state)
 {
 	struct ssd130x_device *ssd130x = drm_to_ssd130x(fb->dev);
-	const struct drm_format_info *fi = drm_format_info(DRM_FORMAT_RGB332);
+	const struct drm_format_info *fi;
 	unsigned int dst_pitch;
 	struct iosys_map dst;
 
+	fi = drm_format_info(DRM_FORMAT_RGB565);
 	if (!fi)
 		return -EINVAL;
 
 	dst_pitch = drm_format_info_min_pitch(fi, 0, drm_rect_width(rect));
 
 	iosys_map_set_vaddr(&dst, data_array);
-	drm_fb_xrgb8888_to_rgb332(&dst, &dst_pitch, vmap, fb, rect, fmtcnv_state);
+	drm_fb_xrgb8888_to_rgb565be(&dst, &dst_pitch, vmap, fb, rect, fmtcnv_state);
 
 	ssd133x_update_rect(ssd130x, rect, data_array, dst_pitch);
 
@@ -1446,10 +1459,11 @@ static int ssd133x_crtc_atomic_check(struct drm_crtc *crtc,
 	struct ssd130x_device *ssd130x = drm_to_ssd130x(drm);
 	struct drm_crtc_state *crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
 	struct ssd130x_crtc_state *ssd130x_state = to_ssd130x_crtc_state(crtc_state);
-	const struct drm_format_info *fi = drm_format_info(DRM_FORMAT_RGB332);
+	const struct drm_format_info *fi;
 	unsigned int pitch;
 	int ret;
 
+	fi = drm_format_info(DRM_FORMAT_RGB565);
 	if (!fi)
 		return -EINVAL;
 
-- 
2.55.0