From: Alan Stern <stern@rowland.harvard.edu>
To: AceLan Kao <acelan.kao@canonical.com>
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>,
Daniel Drake <drake@endlessm.com>, Joe Perches <joe@perches.com>,
Mathias Nyman <mathias.nyman@linux.intel.com>,
<linux-usb@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] usb: core: disable USB2 LPM when suspending
Date: Thu, 20 Sep 2018 10:43:40 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1809201037540.2141-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <20180920070940.14773-1-acelan.kao@canonical.com>
On Thu, 20 Sep 2018, AceLan Kao wrote:
> We found a S5 current leakage issue on Dell DW1820 WiFi/BT combo card
> which uses Qualcomm QCA6174 SoC. It also comes with WiFi and BT failure
> when encountered current leakage issue.
> 1. Power on, both WiFi and BT work.
> 2. Power off and found a current leakage issue(consumes ~0.5W)
> 3. Power on, no WiFi and BT devices can be found in lspci and lsusb.
> 4. Power off, there is no current leakage issue at S5.
> 5. continue to 1.
>
> From Qualcomm's report:
> Based on the USB sniffer log, the difference between Linux and Windows
> is USB LPM setting(no LPM transaction on Windows) which may leads to
> the voltage leakage on Linux S5 state.
>
> After checked the LPM related code and found, when system is going to
> enter S5, it resumes the USB devices from runtime suspend and enables
> USB2 LPM, and then it calls usb_dev_poweroff() -> usb_suspend(), and
> leave USB2 LPM stays enabled.
But usb_suspend() -> usb_suspend_both() -> usb_suspend_device() ->
generic_suspend() -> usb_port_suspend() ->
usb_set_usb2_hardware_lpm(udev, 0). So why does USB2 LPM stay enabled?
> Disable USB2 LPM in usb_suspend() fixes the issue mentioned above,
> and try 30 times of s2idle, S3 and S5, the USB devices keep working
> well. Disable USB2 LPM seems do no harm to the system.
>
> Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
> ---
> drivers/usb/core/driver.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> index e76e95f62f76..ac5e60d7104f 100644
> --- a/drivers/usb/core/driver.c
> +++ b/drivers/usb/core/driver.c
> @@ -1463,6 +1463,9 @@ int usb_suspend(struct device *dev, pm_message_t msg)
> struct usb_device *udev = to_usb_device(dev);
> int r;
>
> + if (udev->usb2_hw_lpm_enabled == 1)
> + usb_set_usb2_hardware_lpm(udev, 0);
At this point the device may still be in runtime suspend. Is that
really okay?
Alan Stern
> +
> unbind_no_pm_drivers_interfaces(udev);
>
> /* From now on we are sure all drivers support suspend/resume
>
next prev parent reply other threads:[~2018-09-20 14:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-20 7:09 [PATCH] usb: core: disable USB2 LPM when suspending AceLan Kao
2018-09-20 14:43 ` Alan Stern [this message]
2018-09-27 2:28 ` AceLan Kao
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