linux-kernel - [PATCH 5.10 144/717] drm/meson: dw-hdmi: Ensure that clocks are enabled before touching the TOP registers

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Date:   Mon, 28 Dec 2020 13:42:22 +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, Marc Zyngier <maz@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 144/717] drm/meson: dw-hdmi: Ensure that clocks are enabled before touching the TOP registers

From: Marc Zyngier <maz@...nel.org>

[ Upstream commit b33340e33acdfe5ca6a5aa1244709575ae1e0432 ]

Removing the meson-dw-hdmi module and re-inserting it results in a hang
as the driver writes to HDMITX_TOP_SW_RESET. Similar effects can be seen
when booting with mainline u-boot and using the u-boot provided DT (which
is highly desirable).

The reason for the hang seem to be that the clocks are not always
enabled by the time we enter meson_dw_hdmi_init(). Moving this call
*after* dw_hdmi_probe() ensures that the clocks are enabled.

Fixes: 1374b8375c2e ("drm/meson: dw_hdmi: add resume/suspend hooks")
Signed-off-by: Marc Zyngier <maz@...nel.org>
Acked-by: Neil Armstrong <narmstrong@...libre.com>
Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201116200744.495826-5-maz@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/meson/meson_dw_hdmi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
index 68826cf9993fc..7f8eea4941472 100644
--- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
+++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
@@ -1073,8 +1073,6 @@ static int meson_dw_hdmi_bind(struct device *dev, struct device *master,
 
 	DRM_DEBUG_DRIVER("encoder initialized\n");
 
-	meson_dw_hdmi_init(meson_dw_hdmi);
-
 	/* Bridge / Connector */
 
 	dw_plat_data->priv_data = meson_dw_hdmi;
@@ -1097,6 +1095,8 @@ static int meson_dw_hdmi_bind(struct device *dev, struct device *master,
 	if (IS_ERR(meson_dw_hdmi->hdmi))
 		return PTR_ERR(meson_dw_hdmi->hdmi);
 
+	meson_dw_hdmi_init(meson_dw_hdmi);
+
 	next_bridge = of_drm_find_bridge(pdev->dev.of_node);
 	if (next_bridge)
 		drm_bridge_attach(encoder, next_bridge,
-- 
2.27.0