linux-kernel - [PATCH v2] USB: Don't enable LPM if it's already enabled

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Message-Id: <20181031055209.11031-1-kai.heng.feng@canonical.com>
Date:   Wed, 31 Oct 2018 13:52:09 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kai-Heng Feng <kai.heng.feng@...onical.com>
Subject: [PATCH v2] USB: Don't enable LPM if it's already enabled

USB Bluetooth controller QCA ROME (0cf3:e007) sometimes stops working
after S3:
[ 165.110742] Bluetooth: hci0: using NVM file: qca/nvm_usb_00000302.bin
[ 168.432065] Bluetooth: hci0: Failed to send body at 4 of 1953 (-110)

After some experiments, I found that disabling LPM can workaround the
issue.

On some platforms, the USB power is cut during S3, so the driver uses
reset-resume to resume the device. During port resume, LPM gets enabled
twice, by usb_reset_and_verify_device() and usb_port_resume().

So let's enable LPM for just once, as this solves the issue for the
device in question.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
---
v2:
 -  Check udev->usb2_hw_lpm_enabled before calling usb_port_resume().

 drivers/usb/core/hub.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index c6077d582d29..02fa574e98ce 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3523,7 +3523,8 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
 		hub_port_logical_disconnect(hub, port1);
 	} else  {
 		/* Try to enable USB2 hardware LPM */
-		if (udev->usb2_hw_lpm_capable == 1)
+		if (udev->usb2_hw_lpm_capable == 1 &&
+		    !udev->usb2_hw_lpm_enabled)
 			usb_set_usb2_hardware_lpm(udev, 1);
 
 		/* Try to enable USB3 LTM */
-- 
2.19.1