drm/st7571-i2c: add support for 2bit grayscale for XRGB8888

Add support for 2bit grayscale and use it for XRGB8888 when grayscale is
supported.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Link: https://lore.kernel.org/r/20250721-st7571-format-v2-6-159f4134098c@gmail.com
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

diff --git a/drivers/gpu/drm/sitronix/st7571-i2c.c b/drivers/gpu/drm/sitronix/st7571-i2c.c
index 807bea62d96e3c37dfeba827dab6470873438fd9..a6c4a6738dedf5881328414e9d8810d3af2a6fe4 100644 (file)
--- a/drivers/gpu/drm/sitronix/st7571-i2c.c
+++ b/drivers/gpu/drm/sitronix/st7571-i2c.c
@@ -219,10 +219,11 @@ static int st7571_send_command_list(struct st7571_device *st7571,
        return ret;
 }
 
-static inline u8 st7571_transform_xy(const char *p, int x, int y)
+static inline u8 st7571_transform_xy(const char *p, int x, int y, u8 bpp)
 {
        int xrest = x % 8;
        u8 result = 0;
+       u8 row_len = 16 * bpp;
 
        /*
         * Transforms an (x, y) pixel coordinate into a vertical 8-bit
@@ -237,7 +238,7 @@ static inline u8 st7571_transform_xy(const char *p, int x, int y)
 
        for (int i = 0; i < 8; i++) {
                int row_idx = y + i;
-               u8 byte = p[row_idx * 16 + x];
+               u8 byte = p[row_idx * row_len + x];
                u8 bit = (byte >> xrest) & 1;
 
                result |= (bit << i);
@@ -304,11 +305,11 @@ static void st7571_prepare_buffer_grayscale(struct st7571_device *st7571,
        struct iosys_map dst;
 
        switch (fb->format->format) {
-       case DRM_FORMAT_XRGB8888: /* Only support XRGB8888 in monochrome mode */
-               dst_pitch = DIV_ROUND_UP(drm_rect_width(rect), 8);
+       case DRM_FORMAT_XRGB8888:
+               dst_pitch = DIV_ROUND_UP(drm_rect_width(rect), 4);
                iosys_map_set_vaddr(&dst, st7571->hwbuf);
 
-               drm_fb_xrgb8888_to_mono(&dst, &dst_pitch, vmap, fb, rect, fmtcnv_state);
+               drm_fb_xrgb8888_to_gray2(&dst, &dst_pitch, vmap, fb, rect, fmtcnv_state);
                break;
 
        case DRM_FORMAT_R1:
@@ -334,7 +335,7 @@ static int st7571_fb_update_rect_monochrome(struct drm_framebuffer *fb, struct d
 
        for (int y = rect->y1; y < rect->y2; y += ST7571_PAGE_HEIGHT) {
                for (int x = rect->x1; x < rect->x2; x++)
-                       row[x] = st7571_transform_xy(st7571->hwbuf, x, y);
+                       row[x] = st7571_transform_xy(st7571->hwbuf, x, y, 1);
 
                st7571_set_position(st7571, rect->x1, y);
 
@@ -359,14 +360,13 @@ static int st7571_fb_update_rect_grayscale(struct drm_framebuffer *fb, struct dr
        rect->y2 = min_t(unsigned int, round_up(rect->y2, ST7571_PAGE_HEIGHT), st7571->nlines);
 
        switch (format) {
-       case DRM_FORMAT_XRGB8888:
-               /* Threated as monochrome (R1) */
-               fallthrough;
        case DRM_FORMAT_R1:
-               x1 = rect->x1;
-               x2 = rect->x2;
+               x1 = rect->x1 * 1;
+               x2 = rect->x2 * 1;
                break;
        case DRM_FORMAT_R2:
+               fallthrough;
+       case DRM_FORMAT_XRGB8888:
                x1 = rect->x1 * 2;
                x2 = rect->x2 * 2;
                break;
@@ -374,7 +374,7 @@ static int st7571_fb_update_rect_grayscale(struct drm_framebuffer *fb, struct dr
 
        for (int y = rect->y1; y < rect->y2; y += ST7571_PAGE_HEIGHT) {
                for (int x = x1; x < x2; x++)
-                       row[x] = st7571_transform_xy(st7571->hwbuf, x, y);
+                       row[x] = st7571_transform_xy(st7571->hwbuf, x, y, 2);
 
                st7571_set_position(st7571, rect->x1, y);
 
@@ -395,7 +395,7 @@ static int st7571_fb_update_rect_grayscale(struct drm_framebuffer *fb, struct dr
                         * For monochrome formats, write the same value twice to get
                         * either a black or white pixel.
                         */
-                       if (format == DRM_FORMAT_R1 || format == DRM_FORMAT_XRGB8888)
+                       if (format == DRM_FORMAT_R1)
                                regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE, row + x, 1);
                }
        }