linux-kernel - Re: [PATCH 4.14 49/62] Bluetooth: btusb: Only check needs_reset

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Date:   Tue, 15 May 2018 12:42:36 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Brian Norris <briannorris@...omium.org>
Cc:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jeremy Cline <jcline@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Marcel Holtmann <marcel@...tmann.org>
Subject: Re: [PATCH 4.14 49/62] Bluetooth: btusb: Only check
 needs_reset_resume DMI table for QCA rome chipsets

On Tue, May 15, 2018 at 10:07:02AM -0700, Brian Norris wrote:
> + Guenter
> 
> On Mon, May 14, 2018 at 08:49:05AM +0200, Greg Kroah-Hartman wrote:
> > 4.14-stable review patch.  If anyone has any objections, please let me know.
> 
> FYI, this backport is wrong. See below.
> 
> > ------------------
> > 
> > From: Hans de Goede <hdegoede@...hat.com>
> > 
> > commit fc54910280eb38bde923cdf0898e74687d8e6989 upstream.
> > 
> > Jeremy Cline correctly points out in rhbz#1514836 that a device where the
> > QCA rome chipset needs the USB_QUIRK_RESET_RESUME quirk, may also ship
> > with a different wifi/bt chipset in some configurations.
> > 
> > If that is the case then we are needlessly penalizing those other chipsets
> > with a reset-resume quirk, typically causing 0.4W extra power use because
> > this disables runtime-pm.
> > 
> > This commit moves the DMI table check to a btusb_check_needs_reset_resume()
> > helper (so that we can easily also call it for other chipsets) and calls
> > this new helper only for QCA_ROME chipsets for now.
> > 
> > BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1514836
> > Cc: stable@...r.kernel.org
> > Cc: Jeremy Cline <jcline@...hat.com>
> > Suggested-by: Jeremy Cline <jcline@...hat.com>
> > Signed-off-by: Hans de Goede <hdegoede@...hat.com>
> > Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > ---
> >  drivers/bluetooth/btusb.c |   10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > --- a/drivers/bluetooth/btusb.c
> > +++ b/drivers/bluetooth/btusb.c
> > @@ -2902,6 +2902,12 @@ static int btusb_config_oob_wake(struct
> >  }
> >  #endif
> >  
> > +static void btusb_check_needs_reset_resume(struct usb_interface *intf)
> > +{
> > +	if (dmi_check_system(btusb_needs_reset_resume_table))
> > +		interface_to_usbdev(intf)->quirks |= USB_QUIRK_RESET_RESUME;
> > +}
> > +
> >  static int btusb_probe(struct usb_interface *intf,
> >  		       const struct usb_device_id *id)
> >  {
> > @@ -3037,9 +3043,6 @@ static int btusb_probe(struct usb_interf
> >  	hdev->send   = btusb_send_frame;
> >  	hdev->notify = btusb_notify;
> >  
> > -	if (dmi_check_system(btusb_needs_reset_resume_table))
> > -		interface_to_usbdev(intf)->quirks |= USB_QUIRK_RESET_RESUME;
> > -
> >  #ifdef CONFIG_PM
> >  	err = btusb_config_oob_wake(hdev);
> >  	if (err)
> > @@ -3177,6 +3180,7 @@ static int btusb_probe(struct usb_interf
> >  			hdev->setup = btusb_setup_csr;
> >  
> >  		set_bit(HCI_QUIRK_SIMULTANEOUS_DISCOVERY, &hdev->quirks);
> > +		btusb_check_needs_reset_resume(intf);
> 
> The original code puts this under the BTUSB_QCA_ROME section, but this
> is getting placed under the BTUSB_CSR section.
> 
Turns out 4.16.y has the same problem. Maybe git got confused because
mainline also has
	set_bit(HCI_QUIRK_SIMULTANEOUS_DISCOVERY, &hdev->quirks);
in the BTUSB_QCA_ROME section. This is missing in 4.14.y and 4.16.y.

Guenter