linux-kernel - [PATCH 4.20 42/88] drm/sun4i: hdmi: Fix usage of TMDS clock

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Message-Id: <20190304081632.237641909@linuxfoundation.org>
Date:   Mon,  4 Mar 2019 09:22:25 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Priit Laes <priit.laes@....com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.20 42/88] drm/sun4i: hdmi: Fix usage of TMDS clock

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 5e1bc251cebc84b41b8eb5d2434e54d939a85430 ]

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>
[Maxime: Moved the TMDS clock enable earlier]
Signed-off-by: Maxime Ripard <maxime.ripard@...tlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190122073232.7240-1-plaes@plaes.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 061d2e0d9011e..416da53767018 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)
@@ -102,6 +104,8 @@ static void sun4i_hdmi_enable(struct drm_encoder *encoder)
 
 	DRM_DEBUG_DRIVER("Enabling the HDMI Output\n");
 
+	clk_prepare_enable(hdmi->tmds_clk);
+
 	sun4i_hdmi_setup_avi_infoframes(hdmi, mode);
 	val |= SUN4I_HDMI_PKT_CTRL_TYPE(0, SUN4I_HDMI_PKT_AVI);
 	val |= SUN4I_HDMI_PKT_CTRL_TYPE(1, SUN4I_HDMI_PKT_END);
-- 
2.19.1