drm/sun4i: dotclock: Fix clock rate read back calcation
When reading back the divider set in the register, we mask off the
bits that aren't part of the divider. Unfortunately the mask used
here was not converted from the field width.
Fix this by converting the field width to a proper bit mask.
Fixes: 9026e0d122ac ("drm: Add Allwinner A10 Display Engine support")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/drivers/gpu/drm/sun4i/sun4i_dotclock.c b/drivers/gpu/drm/sun4i/sun4i_dotclock.c
index 4332da4..1b6c225 100644
--- a/drivers/gpu/drm/sun4i/sun4i_dotclock.c
+++ b/drivers/gpu/drm/sun4i/sun4i_dotclock.c
@@ -62,7 +62,7 @@
regmap_read(dclk->regmap, SUN4I_TCON0_DCLK_REG, &val);
val >>= SUN4I_TCON0_DCLK_DIV_SHIFT;
- val &= SUN4I_TCON0_DCLK_DIV_WIDTH;
+ val &= (1 << SUN4I_TCON0_DCLK_DIV_WIDTH) - 1;
if (!val)
val = 1;