linux-kernel - Re: [PATCH v4] USB: Don't enable LPM if it's already enabled

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Date:   Mon, 7 Jan 2019 17:16:20 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] USB: Don't enable LPM if it's already enabled

On Mon, Dec 03, 2018 at 06:26:43PM +0800, Kai-Heng Feng wrote:
> 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.
> 
> Also consolidate USB2 LPM functions to usb_enable_usb2_hardware_lpm()
> and usb_disable_usb2_hardware_lpm().
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>

What kernel patch does this one "fix"?  Adding a "Fixes:" tag would be
good to try to figure out how far back in the kernel releases this
should be backported.

thanks,

greg k-h