linux-kernel - Re: [PATCH] USB: Disable USB2 LPM at shutdown

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Date:   Fri, 23 Nov 2018 16:06:18 +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] USB: Disable USB2 LPM at shutdown

On Wed, Nov 07, 2018 at 01:34:01AM +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.
> 
> Disalbe LPM at shutdown can 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@...onical.com>
> ---
>  drivers/usb/core/port.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> index 1a06a4b5fbb1..15f6924a4d84 100644
> --- a/drivers/usb/core/port.c
> +++ b/drivers/usb/core/port.c
> @@ -285,6 +285,15 @@ 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_set_usb2_hardware_lpm(port_dev->child, 0);

Shouldn't you also test if child->usb2_hw_lpm_enabled before calling
this?

Or at the least usb2_hw_lpm_capable?

You did test this on a bunch of USB 1 and USB 3 devices, right?

thanks,

greg k-h