linux-kernel - [PATCH 5.9 125/252] drm: bridge: dw-hdmi: Avoid resetting force in the detect function

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Date:   Mon, 23 Nov 2020 13:21:15 +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, Jonathan Liu <net147@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.9 125/252] drm: bridge: dw-hdmi: Avoid resetting force in the detect function

From: Jonathan Liu <net147@...il.com>

[ Upstream commit bc551d776b691022f49b5bb5379bd58f7c4eb76a ]

It has been observed that resetting force in the detect function can
result in the PHY being powered down in response to hot-plug detect
being asserted, even when the HDMI connector is forced on.

Enabling debug messages and adding a call to dump_stack() in
dw_hdmi_phy_power_off() shows the following in dmesg:
[  160.637413] dwhdmi-rockchip ff940000.hdmi: EVENT=plugin
[  160.637433] dwhdmi-rockchip ff940000.hdmi: PHY powered down in 0 iterations

Call trace:
dw_hdmi_phy_power_off
dw_hdmi_phy_disable
dw_hdmi_update_power
dw_hdmi_detect
dw_hdmi_connector_detect
drm_helper_probe_detect_ctx
drm_helper_hpd_irq_event
dw_hdmi_irq
irq_thread_fn
irq_thread
kthread
ret_from_fork

Fixes: 381f05a7a842 ("drm: bridge/dw_hdmi: add connector mode forcing")
Signed-off-by: Jonathan Liu <net147@...il.com>
Reviewed-by: Sam Ravnborg <sam@...nborg.org>
Signed-off-by: Sam Ravnborg <sam@...nborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201031081747.372599-1-net147@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 748df1cacd2b7..0c79a9ba48bb6 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -2327,12 +2327,6 @@ static enum drm_connector_status dw_hdmi_detect(struct dw_hdmi *hdmi)
 {
 	enum drm_connector_status result;
 
-	mutex_lock(&hdmi->mutex);
-	hdmi->force = DRM_FORCE_UNSPECIFIED;
-	dw_hdmi_update_power(hdmi);
-	dw_hdmi_update_phy_mask(hdmi);
-	mutex_unlock(&hdmi->mutex);
-
 	result = hdmi->phy.ops->read_hpd(hdmi, hdmi->phy.data);
 
 	mutex_lock(&hdmi->mutex);
-- 
2.27.0