linux-kernel - [PATCH] phy: qcom-usb-hs: Fix extcon double register after power cycle

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Date:   Tue,  8 Oct 2019 13:52:08 +0200
From:   Stephan Gerhold <stephan@...hold.net>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Chanwoo Choi <cw00.choi@...sung.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stephan Gerhold <stephan@...hold.net>
Subject: [PATCH] phy: qcom-usb-hs: Fix extcon double register after power cycle

Commit f0b5c2c96370 ("phy: qcom-usb-hs: Replace the extcon API")
switched from extcon_register_notifier() to the resource-managed
API, i.e. devm_extcon_register_notifier().

This is problematic in this case, because the extcon notifier
is dynamically registered/unregistered whenever the PHY is powered
on/off. The resource-managed API does not unregister the notifier
until the driver is removed, so as soon as the PHY is power cycled,
attempting to register the notifier again results in:

	double register detected
	WARNING: CPU: 1 PID: 182 at kernel/notifier.c:26 notifier_chain_register+0x74/0xa0
	Call trace:
	 ...
	 extcon_register_notifier+0x74/0xb8
	 devm_extcon_register_notifier+0x54/0xb8
	 qcom_usb_hs_phy_power_on+0x1fc/0x208
	 ...

... and USB stops working after plugging the cable out and in
another time.

The easiest way to fix this is to make a partial revert of
commit f0b5c2c96370 ("phy: qcom-usb-hs: Replace the extcon API")
and avoid using the resource-managed API in this case.

Fixes: f0b5c2c96370 ("phy: qcom-usb-hs: Replace the extcon API")
Signed-off-by: Stephan Gerhold <stephan@...hold.net>
---
An other way to fix this would be keep the extcon notifier
permanently registered, and check in qcom_usb_hs_phy_vbus_notifier
if the PHY is currently powered on.
---
 drivers/phy/qualcomm/phy-qcom-usb-hs.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/qualcomm/phy-qcom-usb-hs.c b/drivers/phy/qualcomm/phy-qcom-usb-hs.c
index b163b3a1558d..61054272a7c8 100644
--- a/drivers/phy/qualcomm/phy-qcom-usb-hs.c
+++ b/drivers/phy/qualcomm/phy-qcom-usb-hs.c
@@ -158,8 +158,8 @@ static int qcom_usb_hs_phy_power_on(struct phy *phy)
 		/* setup initial state */
 		qcom_usb_hs_phy_vbus_notifier(&uphy->vbus_notify, state,
 					      uphy->vbus_edev);
-		ret = devm_extcon_register_notifier(&ulpi->dev, uphy->vbus_edev,
-				EXTCON_USB, &uphy->vbus_notify);
+		ret = extcon_register_notifier(uphy->vbus_edev, EXTCON_USB,
+					       &uphy->vbus_notify);
 		if (ret)
 			goto err_ulpi;
 	}
@@ -180,6 +180,9 @@ static int qcom_usb_hs_phy_power_off(struct phy *phy)
 {
 	struct qcom_usb_hs_phy *uphy = phy_get_drvdata(phy);
 
+	if (uphy->vbus_edev)
+		extcon_unregister_notifier(uphy->vbus_edev, EXTCON_USB,
+					   &uphy->vbus_notify);
 	regulator_disable(uphy->v3p3);
 	regulator_disable(uphy->v1p8);
 	clk_disable_unprepare(uphy->sleep_clk);
-- 
2.23.0