[PATCH v2] drm/panel/panel-sitronix-st7701: Fix RTNI calculation

[Marek Vasut]

The RTNI field is multiplied by 16 and incremented by 512 before being
used as the minimum number of pixel clock per horizontal line, hence
it is necessary to subtract those 512 bytes from htotal and then divide
the result by 16 before writing the value into the RTNI field. Fix the
calculation.

Fixes: de2b4917843c ("drm/panel/panel-sitronix-st7701: Infer horizontal pixel count from TFT mode")
Signed-off-by: Marek Vasut <marex at denx.de>
---
Cc: Guido Günther <agx at sigxcpu.org>
Cc: Jagan Teki <jagan at amarulasolutions.com>
Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Cc: Linus Walleij <linus.walleij at linaro.org>
Cc: Sam Ravnborg <sam at ravnborg.org>
Cc: Thierry Reding <thierry.reding at gmail.com>
---
V2: Clamp the htotal to range 512...1008, so RTNI always fits the bitfield
---
 drivers/gpu/drm/panel/panel-sitronix-st7701.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7701.c b/drivers/gpu/drm/panel/panel-sitronix-st7701.c
index c481daa4bbceb..9578f461f5e48 100644
--- a/drivers/gpu/drm/panel/panel-sitronix-st7701.c
+++ b/drivers/gpu/drm/panel/panel-sitronix-st7701.c
@@ -244,7 +244,7 @@ static void st7701_init_sequence(struct st7701 *st7701)
 		   DSI_CMD2_BK0_INVSEL_ONES_MASK |
 		   FIELD_PREP(DSI_CMD2_BK0_INVSEL_NLINV_MASK, desc->nlinv),
 		   FIELD_PREP(DSI_CMD2_BK0_INVSEL_RTNI_MASK,
-			      DIV_ROUND_UP(mode->htotal, 16)));
+			      (clamp((u32)mode->htotal, 512U, 1008U) - 512) / 16));
 
 	/* Command2, BK1 */
 	ST7701_DSI(st7701, DSI_CMD2BKX_SEL,
-- 
2.35.1