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

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Message-ID: <20181123150804.GB17386@kroah.com>
Date:   Fri, 23 Nov 2018 16:08:04 +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 v2] USB: Don't enable LPM if it's already enabled

On Wed, Oct 31, 2018 at 01:52:09PM +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.
> 
> 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);

It's annoying how every caller has to try to figure this out, why can't
we put this logic in the usb_set_usb2_hardware_lpm() itself?

And usb_set_usb2_hardware_lpm() is a horrid name, as it has a bool
option that you always have to look up.  We should just have
usb_usb2_hardware_lpm_enable() and usb_usb2_hardware_lpm_disable().

Care to make this a patch series to fix all of this up?

thanks,

greg k-h