lkml.org 
[lkml]   [2020]   [Jun]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/2] xhci: Poll for U0 after disabling USB2 LPM
From
Date


> On May 20, 2020, at 18:18, Kai-Heng Feng <kai.heng.feng@canonical.com> wrote:
>
> USB2 devices with LPM enabled may interrupt the system suspend:
> [ 932.510475] usb 1-7: usb suspend, wakeup 0
> [ 932.510549] hub 1-0:1.0: hub_suspend
> [ 932.510581] usb usb1: bus suspend, wakeup 0
> [ 932.510590] xhci_hcd 0000:00:14.0: port 9 not suspended
> [ 932.510593] xhci_hcd 0000:00:14.0: port 8 not suspended
> ..
> [ 932.520323] xhci_hcd 0000:00:14.0: Port change event, 1-7, id 7, portsc: 0x400e03
> ..
> [ 932.591405] PM: pci_pm_suspend(): hcd_pci_suspend+0x0/0x30 returns -16
> [ 932.591414] PM: dpm_run_callback(): pci_pm_suspend+0x0/0x160 returns -16
> [ 932.591418] PM: Device 0000:00:14.0 failed to suspend async: error -16
>
> During system suspend, USB core will let HC suspends the device if it
> doesn't have remote wakeup enabled and doesn't have any children.
> However, from the log above we can see that the usb 1-7 doesn't get bus
> suspended due to not in U0. After a while the port finished U2 -> U0
> transition, interrupts the suspend process.
>
> The observation is that after disabling LPM, port doesn't transit to U0
> immediately and can linger in U2. xHCI spec 4.23.5.2 states that the
> maximum exit latency for USB2 LPM should be BESL + 10us. The BESL for
> the affected device is advertised as 400us, which is still not enough
> based on my testing result.
>
> So let's use the maximum permitted latency, 10000, to poll for U0
> status to solve the issue.
>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>

A gentle ping...

> ---
> drivers/usb/host/xhci.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 14181a7ea375..1058f604975b 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -4474,6 +4474,9 @@ static int xhci_set_usb2_hardware_lpm(struct usb_hcd *hcd,
> mutex_lock(hcd->bandwidth_mutex);
> xhci_change_max_exit_latency(xhci, udev, 0);
> mutex_unlock(hcd->bandwidth_mutex);
> + readl_poll_timeout(ports[port_num]->addr, pm_val,
> + (pm_val & PORT_PLS_MASK) == XDEV_U0,
> + 100, 10000);
> return 0;
> }
> }
> --
> 2.17.1
>

\
 
 \ /
  Last update: 2020-06-08 05:59    [W:0.084 / U:0.196 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site