drm/mipi_dbi: Add support for display offsets

If the resolution of the TFT display is smaller than the maximum
resolution supported by the display controller, the display may be
connected to the driver output arrays with a horizontal and/or vertical
offset, leading to a shifted image.

Add support for specifying these offsets.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200115124548.3951-4-geert+renesas@glider.be

drivers/gpu/drm/drm_mipi_dbi.c

@@ -238,6 +238,23 @@ int mipi_dbi_buf_copy(void *dst, struct drm_framebuffer *fb,
 }
 EXPORT_SYMBOL(mipi_dbi_buf_copy);
 
+static void mipi_dbi_set_window_address(struct mipi_dbi_dev *dbidev,
+					unsigned int xs, unsigned int xe,
+					unsigned int ys, unsigned int ye)
+{
+	struct mipi_dbi *dbi = &dbidev->dbi;
+
+	xs += dbidev->left_offset;
+	xe += dbidev->left_offset;
+	ys += dbidev->top_offset;
+	ye += dbidev->top_offset;
+
+	mipi_dbi_command(dbi, MIPI_DCS_SET_COLUMN_ADDRESS, (xs >> 8) & 0xff,
+			 xs & 0xff, (xe >> 8) & 0xff, xe & 0xff);
+	mipi_dbi_command(dbi, MIPI_DCS_SET_PAGE_ADDRESS, (ys >> 8) & 0xff,
+			 ys & 0xff, (ye >> 8) & 0xff, ye & 0xff);
+}
+
 static void mipi_dbi_fb_dirty(struct drm_framebuffer *fb, struct drm_rect *rect)
 {
 	struct drm_gem_object *gem = drm_gem_fb_get_obj(fb, 0);
@@ -271,12 +288,8 @@ static void mipi_dbi_fb_dirty(struct drm_framebuffer *fb, struct drm_rect *rect)
 		tr = cma_obj->vaddr;
 	}
 
-	mipi_dbi_command(dbi, MIPI_DCS_SET_COLUMN_ADDRESS,
-			 (rect->x1 >> 8) & 0xff, rect->x1 & 0xff,
-			 ((rect->x2 - 1) >> 8) & 0xff, (rect->x2 - 1) & 0xff);
-	mipi_dbi_command(dbi, MIPI_DCS_SET_PAGE_ADDRESS,
-			 (rect->y1 >> 8) & 0xff, rect->y1 & 0xff,
-			 ((rect->y2 - 1) >> 8) & 0xff, (rect->y2 - 1) & 0xff);
+	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);
@@ -366,10 +379,7 @@ static void mipi_dbi_blank(struct mipi_dbi_dev *dbidev)
 
 	memset(dbidev->tx_buf, 0, len);
 
-	mipi_dbi_command(dbi, MIPI_DCS_SET_COLUMN_ADDRESS, 0, 0,
-			 ((width - 1) >> 8) & 0xFF, (width - 1) & 0xFF);
-	mipi_dbi_command(dbi, MIPI_DCS_SET_PAGE_ADDRESS, 0, 0,
-			 ((height - 1) >> 8) & 0xFF, (height - 1) & 0xFF);
+	mipi_dbi_set_window_address(dbidev, 0, width - 1, 0, height - 1);
 	mipi_dbi_command_buf(dbi, MIPI_DCS_WRITE_MEMORY_START,
 			     (u8 *)dbidev->tx_buf, len);
 

include/drm/drm_mipi_dbi.h

@@ -109,6 +109,18 @@ struct mipi_dbi_dev {
 	 */
 	unsigned int rotation;
 
+	/**
+	 * @left_offset: Horizontal offset of the display relative to the
+	 *               controller's driver array
+	 */
+	unsigned int left_offset;
+
+	/**
+	 * @top_offset: Vertical offset of the display relative to the
+	 *              controller's driver array
+	 */
+	unsigned int top_offset;
+
 	/**
 	 * @backlight: backlight device (optional)
 	 */