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

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Message-Id: <20181030055452.25969-1-kai.heng.feng@canonical.com>
Date:   Tue, 30 Oct 2018 13:54:52 +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] 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>
---
 drivers/usb/core/driver.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 53564386ed57..e11d2eac76b6 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1901,7 +1901,8 @@ int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable)
 	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
 	int ret = -EPERM;
 
-	if (enable && !udev->usb2_hw_lpm_allowed)
+	if (enable && !udev->usb2_hw_lpm_allowed ||
+	    udev->usb2_hw_lpm_enabled == enable)
 		return 0;
 
 	if (hcd->driver->set_usb2_hw_lpm) {
-- 
2.19.1