linux-kernel - Re: [PATCH v3 01/11] usb: phy: Add APIs for runtime power management

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Message-ID: <20130403081532.GE25837@arwen.pp.htv.fi>
Date:	Wed, 3 Apr 2013 11:15:32 +0300
From:	Felipe Balbi <balbi@...com>
To:	Vivek Gautam <gautamvivek1987@...il.com>
CC:	Kishon Vijay Abraham I <kishon@...com>,
	Vivek Gautam <gautam.vivek@...sung.com>, <balbi@...com>,
	<linux-usb@...r.kernel.org>, <linux-samsung-soc@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<gregkh@...uxfoundation.org>, <stern@...land.harvard.edu>,
	<sarah.a.sharp@...ux.intel.com>, <rob.herring@...xeda.com>,
	<kgene.kim@...sung.com>, <dianders@...omium.org>,
	<t.figa@...sung.com>, <p.paneri@...sung.com>
Subject: Re: [PATCH v3 01/11] usb: phy: Add APIs for runtime power management

Hi,

On Wed, Apr 03, 2013 at 11:48:39AM +0530, Vivek Gautam wrote:
> >> Adding  APIs to handle runtime power management on PHY
> >> devices. PHY consumers may need to wake-up/suspend PHYs
> >> when they work across autosuspend.
> >>
> >> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
> >> ---
> >>   include/linux/usb/phy.h |  141
> >> +++++++++++++++++++++++++++++++++++++++++++++++
> >>   1 files changed, 141 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/include/linux/usb/phy.h b/include/linux/usb/phy.h
> >> index 6b5978f..01bf9c1 100644
> >> --- a/include/linux/usb/phy.h
> >> +++ b/include/linux/usb/phy.h
> >> @@ -297,4 +297,145 @@ static inline const char *usb_phy_type_string(enum
> >> usb_phy_type type)
> >>                 return "UNKNOWN PHY TYPE";
> >>         }
> >>   }
> >> +
> >> +static inline void usb_phy_autopm_enable(struct usb_phy *x)
> >> +{
> >> +       if (!x || !x->dev) {
> >> +               dev_err(x->dev, "no PHY or attached device available\n");
> >> +               return;
> >> +               }
> >> +
> >> +       pm_runtime_enable(x->dev);
> >> +}
> >
> >
> > IMO we need not have wrapper APIs for runtime_enable and runtime_disable
> > here. Generally runtime_enable and runtime_disable is done in probe and
> > remove of a driver respectively. So it's better to leave the
> > runtime_enable/runtime_disable to be done in *phy provider* driver than
> > having an API for it to be done by *phy user* driver. Felipe, what do you
> > think?
> 
> Thanks!!
> That's very true, runtime_enable() and runtime_disable() calls are made by
> *phy_provider* only. But a querry here.
> Wouldn't in any case a PHY consumer might want to disable runtime_pm on PHY ?
> Say, when consumer failed to suspend the PHY properly
> (*put_sync(phy->dev)* fails), how much sure is the consumer about the
> state of PHY ?

no no, wait a minute. We might not want to enable runtime pm for the PHY
until the UDC says it can handle runtime pm, no ? I guess this makes a
bit of sense (at least in my head :-p).

Imagine if PHY is runtime suspended but e.g. DWC3 isn't runtime pm
enabled... Does it make sense to leave that control to the USB
controller drivers ?

I'm open for suggestions

-- 
balbi

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