drm/bridge: lt9611: Fix PLL being unable to lock

commit 2a9df204be0bbb896e087f00b9ee3fc559d5a608 upstream.

This fixes PLL being unable to lock, and is derived from an equivalent
downstream commit.

Available LT9611 documentation does not list this register, neither does
LT9611UXC (which is a different chip).

This commit has been confirmed to fix HDMI output on DragonBoard 845c.

Suggested-by: Amit Pundir <amit.pundir@linaro.org>
Reviewed-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221213150304.4189760-1-robert.foss@linaro.org
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c
index 3b77238ca4aff3e89e273412649db7734db11dc6..ae8c6d9d4095f3dcff7966121dc17e67aee8e9f6 100644 (file)
--- a/drivers/gpu/drm/bridge/lontium-lt9611.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
@@ -258,6 +258,7 @@ static int lt9611_pll_setup(struct lt9611 *lt9611, const struct drm_display_mode
                { 0x8126, 0x55 },
                { 0x8127, 0x66 },
                { 0x8128, 0x88 },
+               { 0x812a, 0x20 },
        };
 
        regmap_multi_reg_write(lt9611->regmap, reg_cfg, ARRAY_SIZE(reg_cfg));