From fa08600a6c0b5c7be99d9742a9f5b5a2a5cd1670 Mon Sep 17 00:00:00 2001 From: Chris Morgan Date: Fri, 8 Dec 2023 09:48:45 -0600 Subject: [PATCH] drm/panel: st7701: Fix AVCL calculation [ Upstream commit 799825aa87200ade1ba21db853d1c2ff720dcfe0 ] The AVCL register, according to the datasheet, comes in increments of -0.2v between -4.4v (represented by 0x0) to -5.0v (represented by 0x3). The current calculation is done by adding the defined AVCL value in mV to -4400 and then dividing by 200 to get the register value. Unfortunately if I subtract -4400 from -4400 I get -8800, which divided by 200 gives me -44. If I instead subtract -4400 from -4400 I get 0, which divided by 200 gives me 0. Based on the datasheet this is the expected register value. Fixes: 83b7a8e7e88e ("drm/panel/panel-sitronix-st7701: Parametrize voltage and timing") Signed-off-by: Chris Morgan Reviewed-by: Neil Armstrong Link: https://lore.kernel.org/r/20231208154847.130615-2-macroalpha82@gmail.com Signed-off-by: Neil Armstrong Link: https://patchwork.freedesktop.org/patch/msgid/20231208154847.130615-2-macroalpha82@gmail.com Signed-off-by: Sasha Levin --- 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 0459965..036ac40 100644 --- a/drivers/gpu/drm/panel/panel-sitronix-st7701.c +++ b/drivers/gpu/drm/panel/panel-sitronix-st7701.c @@ -288,7 +288,7 @@ static void st7701_init_sequence(struct st7701 *st7701) FIELD_PREP(DSI_CMD2_BK1_PWRCTRL2_AVDD_MASK, DIV_ROUND_CLOSEST(desc->avdd_mv - 6200, 200)) | FIELD_PREP(DSI_CMD2_BK1_PWRCTRL2_AVCL_MASK, - DIV_ROUND_CLOSEST(-4400 + desc->avcl_mv, 200))); + DIV_ROUND_CLOSEST(-4400 - desc->avcl_mv, 200))); /* T2D = 0.2us * T2D[3:0] */ ST7701_DSI(st7701, DSI_CMD2_BK1_SPD1, -- 2.7.4