From: Alan Stern <stern@rowland.harvard.edu>
To: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: Kai-Heng Feng <kai.heng.feng@canonical.com>,
<gregkh@linuxfoundation.org>, <linux-usb@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] USB: Don't enable LPM if it's already enabled
Date: Tue, 30 Oct 2018 11:00:46 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1810301058540.1515-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <c5d72c60-c13c-8801-26d5-2fe8ab48d98c@linux.intel.com>
On Tue, 30 Oct 2018, Mathias Nyman wrote:
> On 30.10.2018 07:54, 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@canonical.com>
> > ---
> > drivers/usb/core/driver.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> > index 53564386ed57..e11d2eac76b6 100644
> > --- a/drivers/usb/core/driver.c
> > +++ b/drivers/usb/core/driver.c
> > @@ -1901,7 +1901,8 @@ int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable)
> > struct usb_hcd *hcd = bus_to_hcd(udev->bus);
> > int ret = -EPERM;
> >
> > - if (enable && !udev->usb2_hw_lpm_allowed)
> > + if (enable && !udev->usb2_hw_lpm_allowed ||
> > + udev->usb2_hw_lpm_enabled == enable)
> > return 0;
> >
> > if (hcd->driver->set_usb2_hw_lpm) {
> >
>
> Something like that would probably work.
>
> Would it make sense to skip USB2 hw LPM enabling in usb_port_resume() if
> port was just reset (and thus LPM enabled)?
>
> something like this:
>
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -3520,7 +3520,7 @@ 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->reset_resume)
> usb_set_usb2_hardware_lpm(udev, 1);
>
> /* Try to enable USB3 LTM */
Why not simply test whether udev->usb2_hw_lpm_enabled is already true?
if (udev->usb2_hw_lpm_capable == 1 &&
!udev->usb2_hw_lpm_enabled)
Or even put this extra test into usb_set_usb2_hardware_lpm().
Alan Stern
next prev parent reply other threads:[~2018-10-30 15:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-30 5:54 [PATCH] USB: Don't enable LPM if it's already enabled Kai-Heng Feng
2018-10-30 6:16 ` kbuild test robot
2018-10-30 6:30 ` kbuild test robot
2018-10-30 14:24 ` Mathias Nyman
2018-10-30 15:00 ` Alan Stern [this message]
2018-10-30 15:07 ` Kai Heng Feng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Pine.LNX.4.44L0.1810301058540.1515-100000@iolanthe.rowland.org \
--to=stern@rowland.harvard.edu \
--cc=gregkh@linuxfoundation.org \
--cc=kai.heng.feng@canonical.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=mathias.nyman@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).