It turns out that TCON TOP registers in H6 SoC have non-zero reset
value. This may cause issues if bits are not changed during
configuration.

To prevent that, initialize registers to 0.

Signed-off-by: Jernej Skrabec <jernej.skra...@siol.net>
---
 drivers/gpu/drm/sun4i/sun8i_tcon_top.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c 
b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
index 3040a79f298f..37158548b447 100644
--- a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
+++ b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
@@ -167,6 +167,13 @@ static int sun8i_tcon_top_bind(struct device *dev, struct 
device *master,
                goto err_assert_reset;
        }
 
+       /*
+        * At least on H6, some registers have some bits set by default
+        * which may cause issues. Clear them here.
+        */
+       writel(0, regs + TCON_TOP_PORT_SEL_REG);
+       writel(0, regs + TCON_TOP_GATE_SRC_REG);
+
        /*
         * TCON TOP has two muxes, which select parent clock for each TCON TV
         * channel clock. Parent could be either TCON TV or TVE clock. For now
-- 
2.19.1

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