On Thu, 6 Jun 2019, Kai-Heng Feng wrote: > at 15:55, Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> wrote: > > > at 18:22, Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> wrote: > > > >> at 00:01, Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> wrote: > >> > >>>> On Jan 30, 2019, at 16:21, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > >>>> > >>>> 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@xxxxxxxxxxxxx> > >>>>> --- > >>>>> 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. > >>> > >>> Yes I think this should be universally applied. > >>> > >>> I don’t think the bug only happens to one device. Users won’t find this > >>> unless they connect their laptop to a power meter. > >>> > >>> Platform may not completely cut off USB bus power during shutdown, > >>> so the device transits to L1 after system shutdown. Now xHC is disabled > >>> so nothing can bring it back to L0 or L2. > >> > >> It would be great if someone can come up with better ideas. > >> > >> We can also use other approaches, but currently this is the only way I > >> can think of. > > > > Alan and Mathias, > > > > It would be great if you can review this patch, or give me some suggestion. > > Can I get some advice here? > I really think disabling LPM should be universally applied. > > Kai-Heng I agree with Kai-Heng, this seems like a fairly light-weight solution to a reasonable problem. As to the issue of how much it will slow down system shutdowns, I have no idea. Probably not very much, unless somebody has an unusually large number of USB devices plugged in, but only testing can give a real answer. I suppose we could add an HCD flag for host controllers which require this workaround. Either way, it's probably not a very big deal. Alan Stern
