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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Rob Clark <robdclark@gmail.com>,
        Archit Taneja <architt@codeaurora.org>,
        Sean Paul <seanpaul@chromium.org>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.4 08/80] drm/bridge: adv7511: Reset registers on hotplug
Date:   Mon,  3 Sep 2018 18:48:46 +0200
Message-Id: <20180903164934.495603871@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Sean Paul <seanpaul@chromium.org>

[ Upstream commit 5f3417569165a8ee57654217f73e0160312f409c ]

The bridge loses its hw state when the cable is unplugged. If we detect
this case in the hpd handler, reset its state.

Reported-by: Rob Clark <robdclark@gmail.com>
Tested-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180703165648.120401-1-seanpaul@chromium.org
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/i2c/adv7511.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/drivers/gpu/drm/i2c/adv7511.c
+++ b/drivers/gpu/drm/i2c/adv7511.c
@@ -450,6 +450,18 @@ static void adv7511_hpd_work(struct work
 	else
 		status = connector_status_disconnected;
 
+	/*
+	 * The bridge resets its registers on unplug. So when we get a plug
+	 * event and we're already supposed to be powered, cycle the bridge to
+	 * restore its state.
+	 */
+	if (status == connector_status_connected &&
+	    adv7511->connector.status == connector_status_disconnected &&
+	    adv7511->powered) {
+		regcache_mark_dirty(adv7511->regmap);
+		adv7511_power_on(adv7511);
+	}
+
 	if (adv7511->connector.status != status) {
 		adv7511->connector.status = status;
 		drm_kms_helper_hotplug_event(adv7511->connector.dev);