linux-kernel - [PATCH 7/7] drm/sun4i: hdmi: Move PAD_CTRL1 setting to mode

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Message-Id: <20171014040252.9621-8-wens@csie.org>
Date:   Sat, 14 Oct 2017 12:02:52 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        David Airlie <airlied@...ux.ie>
Cc:     Chen-Yu Tsai <wens@...e.org>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: [PATCH 7/7] drm/sun4i: hdmi: Move PAD_CTRL1 setting to mode_set function

Initially we configured the PAD_CTRL1 register at probe/bind time.
However it seems the HDMI controller will modify some of the bits
in this register by itself. On the A10 it is particularly annoying
as it toggles the output invert bits, which inverts the colors on
the display output.

The U-boot driver this driver is based on sets this register twice,
though it seems it's only needed for actual display output. Hence
we move it to the mode_set function.

Signed-off-by: Chen-Yu Tsai <wens@...e.org>
---
 drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
index 027b5608dbe6..6ca6e6a74c4a 100644
--- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
+++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
@@ -144,6 +144,22 @@ static void sun4i_hdmi_mode_set(struct drm_encoder *encoder,
 	writel(SUN4I_HDMI_UNKNOWN_INPUT_SYNC,
 	       hdmi->base + SUN4I_HDMI_UNKNOWN_REG);
 
+	/*
+	 * Setup output pad (?) controls
+	 *
+	 * This is done here instead of at probe/bind time because
+	 * the controller seems to toggle some of the bits on its own.
+	 *
+	 * We can't just initialize the register there, we need to
+	 * protect the clock bits that have already been read out and
+	 * cached by the clock framework.
+	 */
+	val = readl(hdmi->base + SUN4I_HDMI_PAD_CTRL1_REG);
+	val &= SUN4I_HDMI_PAD_CTRL1_HALVE_CLK;
+	val |= hdmi->variant->pad_ctrl1_init_val;
+	writel(val, hdmi->base + SUN4I_HDMI_PAD_CTRL1_REG);
+	val = readl(hdmi->base + SUN4I_HDMI_PAD_CTRL1_REG);
+
 	/* Setup timing registers */
 	writel(SUN4I_HDMI_VID_TIMING_X(mode->hdisplay) |
 	       SUN4I_HDMI_VID_TIMING_Y(mode->vdisplay),
@@ -489,16 +505,6 @@ static int sun4i_hdmi_bind(struct device *dev, struct device *master,
 	writel(hdmi->variant->pad_ctrl0_init_val,
 	       hdmi->base + SUN4I_HDMI_PAD_CTRL0_REG);
 
-	/*
-	 * We can't just initialize the register there, we need to
-	 * protect the clock bits that have already been read out and
-	 * cached by the clock framework.
-	 */
-	reg = readl(hdmi->base + SUN4I_HDMI_PAD_CTRL1_REG);
-	reg &= SUN4I_HDMI_PAD_CTRL1_HALVE_CLK;
-	reg |= hdmi->variant->pad_ctrl1_init_val;
-	writel(reg, hdmi->base + SUN4I_HDMI_PAD_CTRL1_REG);
-
 	reg = readl(hdmi->base + SUN4I_HDMI_PLL_CTRL_REG);
 	reg &= SUN4I_HDMI_PLL_CTRL_DIV_MASK;
 	reg |= hdmi->variant->pll_ctrl_init_val;
-- 
2.14.2