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

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Date:   Sat, 31 Oct 2020 19:17:47 +1100
From:   Jonathan Liu <net147@...il.com>
To:     linux-rockchip@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Liu Ying <victor.liu@....com>,
        Russell King <rmk+kernel@....linux.org.uk>,
        Fabio Estevam <fabio.estevam@...escale.com>,
        Jonathan Liu <net147@...il.com>
Subject: [PATCH] drm: bridge: dw-hdmi: Avoid resetting force in the detect function

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>
---
 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 748df1cacd2b..0c79a9ba48bb 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);
-- 
2.29.1