drm/mipi_dbi: Fix off-by-one bugs in mipi_dbi_blank()

When configuring the frame memory window, the last column and row
numbers are written to the column resp. page address registers.  These
numbers are thus one less than the actual window width resp. height.

While this is handled correctly in mipi_dbi_fb_dirty() since commit
03ceb1c8dfd1e293 ("drm/tinydrm: Fix setting of the column/page end
addresses."), it is not in mipi_dbi_blank().  The latter still forgets
to subtract one when calculating the most significant bytes of the
column and row numbers, thus programming wrong values when the display
width or height is a multiple of 256.

Fixes: 02dd95fe31693626 ("drm/tinydrm: Add MIPI DBI support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191230130604.31006-1-geert+renesas@glider.be

diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
index e34058c721becd6bd78bdf9da0b59446d9bf51e3..16bff1be4b8ac62225265713f3219a17e0dacf39 100644 (file)
--- a/drivers/gpu/drm/drm_mipi_dbi.c
+++ b/drivers/gpu/drm/drm_mipi_dbi.c
@@ -367,9 +367,9 @@ 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 >> 8) & 0xFF, (width - 1) & 0xFF);
+                        ((width - 1) >> 8) & 0xFF, (width - 1) & 0xFF);
        mipi_dbi_command(dbi, MIPI_DCS_SET_PAGE_ADDRESS, 0, 0,
-                        (height >> 8) & 0xFF, (height - 1) & 0xFF);
+                        ((height - 1) >> 8) & 0xFF, (height - 1) & 0xFF);
        mipi_dbi_command_buf(dbi, MIPI_DCS_WRITE_MEMORY_START,
                             (u8 *)dbidev->tx_buf, len);