linux-kernel - [PATCH AUTOSEL 4.19 007/258] drm/sun4i: Initialize registers in tcon-top driver

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Message-Id: <20190128155924.51521-7-sashal@kernel.org>
Date:   Mon, 28 Jan 2019 10:55:13 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jernej Skrabec <jernej.skrabec@...l.net>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sasha Levin <sashal@...nel.org>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 4.19 007/258] drm/sun4i: Initialize registers in tcon-top driver

From: Jernej Skrabec <jernej.skrabec@...l.net>

[ Upstream commit c96d62215fb540e2ae61de44cb7caf4db50958e3 ]

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.skrabec@...l.net>
Signed-off-by: Maxime Ripard <maxime.ripard@...tlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181104182705.18047-24-jernej.skrabec@siol.net
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 d5240b777a8f..adcdf946c365 100644
--- a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
+++ b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
@@ -168,6 +168,13 @@ 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