linux-kernel - [PATCH] drm/sun4i: hdmi: Fix usage of TMDS clock

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Message-Id: <20190122073232.7240-1-plaes@plaes.org>
Date:   Tue, 22 Jan 2019 09:32:32 +0200
From:   Priit Laes <plaes@...es.org>
To:     Maxime Ripard <maxime.ripard@...tlin.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Chen-Yu Tsai <wens@...e.org>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Priit Laes <priit.laes@....com>
Subject: [PATCH] drm/sun4i: hdmi: Fix usage of TMDS clock

From: Priit Laes <priit.laes@....com>

Although TMDS clock is required for HDMI to properly function,
nobody called clk_prepare_enable(). This fixes reference counting
issues and makes sure clock is running when it needs to be running.

Due to TDMS clock being parent clock for DDC clock, TDMS clock
was turned on/off for each EDID probe, causing spurious failures
for certain HDMI/DVI screens.

Fixes: 9c5681011a0c ("drm/sun4i: Add HDMI support")

Signed-off-by: Priit Laes <priit.laes@....com>
---
 drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
index 061d2e0d9011..25f4d676fd82 100644
--- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
+++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
@@ -92,6 +92,8 @@ static void sun4i_hdmi_disable(struct drm_encoder *encoder)
 	val = readl(hdmi->base + SUN4I_HDMI_VID_CTRL_REG);
 	val &= ~SUN4I_HDMI_VID_CTRL_ENABLE;
 	writel(val, hdmi->base + SUN4I_HDMI_VID_CTRL_REG);
+
+	clk_disable_unprepare(hdmi->tmds_clk);
 }
 
 static void sun4i_hdmi_enable(struct drm_encoder *encoder)
@@ -112,6 +114,8 @@ static void sun4i_hdmi_enable(struct drm_encoder *encoder)
 		val |= SUN4I_HDMI_VID_CTRL_HDMI_MODE;
 
 	writel(val, hdmi->base + SUN4I_HDMI_VID_CTRL_REG);
+
+	clk_prepare_enable(hdmi->tmds_clk);
 }
 
 static void sun4i_hdmi_mode_set(struct drm_encoder *encoder,
-- 
2.11.0