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Date:   Wed, 30 Jan 2019 09:21:33 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Kai-Heng Feng <kai.heng.feng@canonical.com>
Cc:     linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] USB: Disable USB2 LPM at shutdown
Message-ID: <20190130082133.GA32660@kroah.com>
References: <20190124061643.11663-1-kai.heng.feng@canonical.com>
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On Thu, Jan 24, 2019 at 02:16:43PM +0800, Kai-Heng Feng wrote:
> The QCA Rome USB Bluetooth controller has several issues once LPM gets
> enabled:
> - Fails to get enumerated in coldboot. [1]
> - Drains more power (~ 0.2W) when the system is in S5. [2]
> - Disappears after a warmboot. [2]
> 
> The issue happens because the device lingers at LPM L1 in S5, so device
> can't get enumerated even after a reboot.
> 
> Disable LPM at shutdown to solve the issue.
> 
> [1] https://bugs.launchpad.net/bugs/1757218
> [2] https://patchwork.kernel.org/patch/10607097/
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
> v2: Use new LPM helpers.
> 
>  drivers/usb/core/port.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> index 1a06a4b5fbb1..bbbb35fa639f 100644
> --- a/drivers/usb/core/port.c
> +++ b/drivers/usb/core/port.c
> @@ -285,6 +285,14 @@ static int usb_port_runtime_suspend(struct device *dev)
>  }
>  #endif
>  
> +static void usb_port_shutdown(struct device *dev)
> +{
> +	struct usb_port *port_dev = to_usb_port(dev);
> +
> +	if (port_dev->child)
> +		usb_disable_usb2_hardware_lpm(port_dev->child);
> +}
> +
>  static const struct dev_pm_ops usb_port_pm_ops = {
>  #ifdef CONFIG_PM
>  	.runtime_suspend =	usb_port_runtime_suspend,
> @@ -301,6 +309,7 @@ struct device_type usb_port_device_type = {
>  static struct device_driver usb_port_driver = {
>  	.name = "usb",
>  	.owner = THIS_MODULE,
> +	.shutdown = usb_port_shutdown,
>  };

So you now do this for all ports in the system, no matter what is
plugged in or not.  Are you _SURE_ you want to do that?  It seems like a
big hammer to solve just one single device's problems.

thanks,

greg k-h