linux-kernel - Re: [PATCH v4 3/3] usb: xhci: plat: Facilitate using autosuspend for xhci plat devices

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Message-ID: <38a8afb8-01f9-46a8-ac87-be1e4ab53136@oss.qualcomm.com>
Date: Wed, 13 Aug 2025 12:19:30 +0530
From: Krishna Kurapati <krishna.kurapati@....qualcomm.com>
To: Peter Chen <hzpeterchen@...il.com>
Cc: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] usb: xhci: plat: Facilitate using autosuspend for
 xhci plat devices



On 8/13/2025 11:46 AM, Peter Chen wrote:
> On Tue, Aug 12, 2025 at 1:58 PM Krishna Kurapati
> <krishna.kurapati@....qualcomm.com> wrote:
>>
>> Allow autosuspend to be used by xhci plat device. For Qualcomm SoCs,
>> when in host mode, it is intended that the controller goes to suspend
>> state to save power and wait for interrupts from connected peripheral
>> to wake it up. This is particularly used in cases where a HID or Audio
>> device is connected. In such scenarios, the usb controller can enter
>> auto suspend and resume action after getting interrupts from the
>> connected device.
>>
>> Signed-off-by: Krishna Kurapati <krishna.kurapati@....qualcomm.com>
>> ---
>>   drivers/usb/host/xhci-plat.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
>> index 5eb51797de32..dd57ffedcaa2 100644
>> --- a/drivers/usb/host/xhci-plat.c
>> +++ b/drivers/usb/host/xhci-plat.c
>> @@ -171,6 +171,7 @@ int xhci_plat_probe(struct platform_device *pdev, struct device *sysdev, const s
>>                  return ret;
>>
>>          pm_runtime_set_active(&pdev->dev);
>> +       pm_runtime_use_autosuspend(&pdev->dev);
>>          pm_runtime_enable(&pdev->dev);
>>          pm_runtime_get_noresume(&pdev->dev);
>>
> 
> There is an xhci quirk XHCI_DEFAULT_PM_RUNTIME_ALLOW for it, try to use it.
> 

Hi Peter,

I see it being used only in xhci-pci.c.

In xhci-plat, I intended to only allow usage of autosuspend and let 
userspace decide whether to use it or not (echo (auto or on) > control).

Hence I only did use_autosuspend() instead of doing runtime_allow.

Regards,
Krishna,