linux-kernel - Re: [RESEND PATCH v2 1/7] usb: xhci: plat: Fix suspend/resume when the optional clk exists

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Date:	Wed, 27 Apr 2016 13:46:23 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Felipe Balbi <felipe.balbi@...ux.intel.com>
CC:	<mathias.nyman@...el.com>, <gregkh@...uxfoundation.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<yendapally.reddy@...adcom.com>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Subject: Re: [RESEND PATCH v2 1/7] usb: xhci: plat: Fix suspend/resume when
 the optional clk exists

Dear Felipe,

On Wed, 27 Apr 2016 08:25:38 +0300 Felipe Balbi wrote:

> Hi,
> 
> (since you're fixing somebody else's commit, it's nice to Cc authors)
> 
> Jisheng Zhang <jszhang@...vell.com> writes:
> > Commit 4718c1774051 ("usb: host: xhci-plat: add clock support") adds
> > optional clk support, but it forgets to prepare/disable and  
>                                           ^^^^^^^^^^^^^^^
>                                           prepare/enable ?
> 
> > enable/unprepare the clk in the resume/suspend path. This path fixes  
>   ^^^^^^^^^^^^^^^^                                          ^^^^
>   disable/unprepare ?                                       patch
> 
> > this issue by adding missing clk related calls.  
> 
> frankly, I'm not sure this patch is entirely correct. At minimum, it's
> not necessarily a bug fix. Original commit had no intent in gating
> clocks during suspend/resume and, IMHO, that might not be what *all*
> XHCI implementations want, though I'm not entirely sure.

Thanks for the hint. Indeed, that's not all xhci-plat users want. I'll drop
this patch in v3.

Thanks a lot for the review,
Jisheng

> 
> > Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> > Fixes: 4718c1774051 ("usb: host: xhci-plat: add clock support")  
> 
> Assuming this is, indeed, a fix; you need to Cc stable here. Just add:
> 
> Cc: <stable@...r.kernel.org> # v3.16+
> 
> > ---
> >  drivers/usb/host/xhci-plat.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> > index 474b5fa..8cb46cb 100644
> > --- a/drivers/usb/host/xhci-plat.c
> > +++ b/drivers/usb/host/xhci-plat.c
> > @@ -295,6 +295,7 @@ static int xhci_plat_remove(struct platform_device *dev)
> >  #ifdef CONFIG_PM_SLEEP
> >  static int xhci_plat_suspend(struct device *dev)
> >  {
> > +	int ret;  
> 
> this would look neater after hcd and xhci declarations below
> 
> >  	struct usb_hcd	*hcd = dev_get_drvdata(dev);
> >  	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
> >  
> > @@ -306,14 +307,25 @@ static int xhci_plat_suspend(struct device *dev)
> >  	 * reconsider this when xhci_plat_suspend enlarges its scope, e.g.,
> >  	 * also applies to runtime suspend.
> >  	 */
> > -	return xhci_suspend(xhci, device_may_wakeup(dev));
> > +	ret = xhci_suspend(xhci, device_may_wakeup(dev));
> > +	if (ret)
> > +		return ret;
> > +
> > +	clk_disable_unprepare(xhci->clk);
> > +
> > +	return ret;
> >  }
> >  
> >  static int xhci_plat_resume(struct device *dev)
> >  {
> > +	int ret;  
> 
> ditto
> 
> >  	struct usb_hcd	*hcd = dev_get_drvdata(dev);
> >  	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
> >  
> > +	ret = clk_prepare_enable(xhci->clk);
> > +	if (ret)
> > +		return ret;
> > +
> >  	return xhci_resume(xhci, 0);
> >  }
> >  
> > -- 
> > 2.8.1
> >
> > --
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