From: Felipe Balbi <balbi@kernel.org>
To: Baolin Wang <baolin.wang@linaro.org>
Cc: mathias.nyman@intel.com, Greg KH <gregkh@linuxfoundation.org>,
Mark Brown <broonie@kernel.org>, USB <linux-usb@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 2/2] usb: dwc3: core: Support the dwc3 host suspend/resume
Date: Thu, 08 Dec 2016 19:52:56 +0200 [thread overview]
Message-ID: <877f7apatj.fsf@linux.intel.com> (raw)
In-Reply-To: <CAMz4ku+wbWb=Ty=eJXKg21KwqGFnrYy3c0Ok3wBthwfOtef8xA@mail.gmail.com>
Hi,
Baolin Wang <baolin.wang@linaro.org> writes:
>> Baolin Wang <baolin.wang@linaro.org> writes:
>>>>> On 28 November 2016 at 14:43, Baolin Wang <baolin.wang@linaro.org> wrote:
>>>>>> For some mobile devices with strict power management, we also want to suspend
>>>>>> the host when the slave is detached for power saving. Thus we add the host
>>>>>> suspend/resume functions to support this requirement.
>>>>>>
>>>>>> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
>>>>>> ---
>>>>>> Changes since v3:
>>>>>> - No updates.
>>>>>>
>>>>>> Changes since v2:
>>>>>> - Remove pm_children_suspended() and other unused macros.
>>>>>>
>>>>>> Changes since v1:
>>>>>> - Add pm_runtime.h head file to avoid kbuild error.
>>>>>> ---
>>>>>> drivers/usb/dwc3/Kconfig | 7 +++++++
>>>>>> drivers/usb/dwc3/core.c | 26 +++++++++++++++++++++++++-
>>>>>> drivers/usb/dwc3/core.h | 15 +++++++++++++++
>>>>>> drivers/usb/dwc3/host.c | 37 +++++++++++++++++++++++++++++++++++++
>>>>>> 4 files changed, 84 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/usb/dwc3/Kconfig b/drivers/usb/dwc3/Kconfig
>>>>>> index a45b4f1..47bb2f3 100644
>>>>>> --- a/drivers/usb/dwc3/Kconfig
>>>>>> +++ b/drivers/usb/dwc3/Kconfig
>>>>>> @@ -47,6 +47,13 @@ config USB_DWC3_DUAL_ROLE
>>>>>>
>>>>>> endchoice
>>>>>>
>>>>>> +config USB_DWC3_HOST_SUSPEND
>>>>>> + bool "Choose if the DWC3 host (xhci) can be suspend/resume"
>>>>>> + depends on USB_DWC3_HOST=y || USB_DWC3_DUAL_ROLE=y
>>>>
>>>> why do you need another Kconfig for this? Just enable it already :-p
>>>
>>> I assume some platforms may do not need this feature. But okay, I can
>>> remove this kconfig and enable it.
>>
>> thanks :-)
>>
>>>>>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>>>>>> index 9a4a5e4..7ad4bc3 100644
>>>>>> --- a/drivers/usb/dwc3/core.c
>>>>>> +++ b/drivers/usb/dwc3/core.c
>>>>>> @@ -1091,6 +1091,7 @@ static int dwc3_probe(struct platform_device *pdev)
>>>>>> pm_runtime_use_autosuspend(dev);
>>>>>> pm_runtime_set_autosuspend_delay(dev, DWC3_DEFAULT_AUTOSUSPEND_DELAY);
>>>>>> pm_runtime_enable(dev);
>>>>>> + pm_suspend_ignore_children(dev, true);
>>>>
>>>> why do you need this?
>>>
>>> Since the dwc3 device is the parent deive of xhci device, if we want
>>> to suspend dwc3 device, we need to suspend child device (xhci device)
>>> manually by issuing pm_runtime_put_sync() in dwc3_host_suspend(). In
>>> pm_runtime_put_sync(), it will check if the children (xhci device) of
>>> dwc3 device have been in suspend state, if not we will suspend dwc3
>>> device failed.
>>>
>>> We get/put the child device manually in parent device's runtime
>>> callback, we need to ignore the child device's runtime state, or it
>>> will failed due to the dependency.
>>
>> I see. Good explanation :-)
>>
>> There's one thing though, if you want to runtime suspend the gadget and
>> dwc3 is working on peripheral mode, host side (XHCI) should already be
>> runtime suspended because there's nothing attached to it. Why isn't it
>> runtime suspended?
>
> Since we have get the runtime count for xHCI device in
> xhci_plat_probe(), in case it will suspend automatically if some
> controllers do not want xHCI enters runtime suspend automatically. So
> the parent device (dwc3 device) need to get/put the xHCI device's
> runtime count to resume/suspend xHCI.
IMHO, that's a bug in xhci-plat, not something dwc3 should work around.
--
balbi
next prev parent reply other threads:[~2016-12-08 17:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-28 6:43 [PATCH v4 1/2] usb: host: plat: Enable xhci plat runtime PM Baolin Wang
2016-11-28 6:43 ` [PATCH v4 2/2] usb: dwc3: core: Support the dwc3 host suspend/resume Baolin Wang
2016-12-08 7:05 ` Baolin Wang
2016-12-08 9:40 ` Felipe Balbi
2016-12-08 10:20 ` Baolin Wang
2016-12-08 11:02 ` Felipe Balbi
2016-12-08 11:14 ` Baolin Wang
2016-12-08 17:52 ` Felipe Balbi [this message]
2016-12-09 3:23 ` Baolin Wang
2016-12-08 7:04 ` [PATCH v4 1/2] usb: host: plat: Enable xhci plat runtime PM Baolin Wang
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