linux-kernel - Re: [RFC PATCH v2 1/3] usb: support Samsung Exynos xHCI Controller

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Date:   Mon, 2 Jan 2023 15:24:48 +0900
From:   Jung Daehwan <dh10.jung@...sung.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Felipe Balbi <balbi@...nel.org>,
        "open list:USB SUBSYSTEM" <linux-usb@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>, sc.suh@...sung.com,
        taehyun.cho@...sung.com, jh0801.jung@...sung.com,
        eomji.oh@...sung.com
Subject: Re: [RFC PATCH v2 1/3] usb: support Samsung Exynos xHCI Controller

On Thu, Dec 29, 2022 at 11:25:58AM +0100, Krzysztof Kozlowski wrote:
> On 29/12/2022 10:57, Daehwan Jung wrote:
> > Currently, dwc3 invokes just xhci platform driver without any data.
> > We add xhci node as child of dwc3 node in order to get data from
> > device tree. It populates "xhci" child by name during initialization
> > of host. This patch only effects if dwc3 node has a child named "xhci"
> > not to disturb original path.
> > 
> > We add "samsung,exynos-xhci" compatible in xhci platform driver
> 
> Where? It is not documented.

I submitted the patch of dt bindings on same patchset.
Is there any missing documentation?

> 
> > to support Exynos SOCs. 
> 
> That's so not true. You do nothing to support Exynos SoC here. Please
> stop pasting incorrect and misleading commit msgs.

I agree misleading commit msgs. I will modify it.

> 
> > We introduce roothub wakeup, which uses roothub
> > as system wakeup source. It needs xhci platform driver to override
> > roothub ops.
> 
> You did not explain why you introduced wakelocks...
> 

I'm sorry I didn't write description enough.
I add it below.

> 
> (...)
> 
> >  	if (shared_hcd) {
> >  		usb_remove_hcd(shared_hcd);
> >  		xhci->shared_hcd = NULL;
> > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> > index 79d7931c048a..693495054001 100644
> > --- a/drivers/usb/host/xhci.c
> > +++ b/drivers/usb/host/xhci.c
> > @@ -5502,6 +5502,10 @@ void xhci_init_driver(struct hc_driver *drv,
> >  			drv->check_bandwidth = over->check_bandwidth;
> >  		if (over->reset_bandwidth)
> >  			drv->reset_bandwidth = over->reset_bandwidth;
> > +		if (over->bus_suspend)
> > +			drv->bus_suspend = over->bus_suspend;
> > +		if (over->bus_resume)
> > +			drv->bus_resume = over->bus_resume;
> >  	}
> >  }
> >  EXPORT_SYMBOL_GPL(xhci_init_driver);
> > diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> > index c9f06c5e4e9d..cb9c54a6a22c 100644
> > --- a/drivers/usb/host/xhci.h
> > +++ b/drivers/usb/host/xhci.h
> > @@ -1752,6 +1752,8 @@ struct xhci_hub {
> >  struct xhci_hcd {
> >  	struct usb_hcd *main_hcd;
> >  	struct usb_hcd *shared_hcd;
> > +	struct wakeup_source *main_wakelock;
> > +	struct wakeup_source *shared_wakelock;
> 
> Drop wakelocks. This is not related to USB and not needed here. Do you
> see anywhere else in core kernel code usage of the wakelocks?
> 
> You got this comment already, didn't you? So why you do not address it?
> 

I want to add a new feature in xhci platform driver. I want to make it
possible to enter system sleep while usb host connected like USB Mouse.
It gets system enter sleep only if there's no usb transaction at all.
Deciding if there's tranaction or not is in root hub because it's parent
of all child usb devices.

Best Regards,
Jung Daehwan

> Best regards,
> Krzysztof
> 
>