linux-kernel - Re: [PATCH v7 1/2] usb: host: xhci-plat: Get PHYs for xhci's hcds

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Message-ID: <CAFp+6iHVWuiTfc4n8LeYkYhmMXA76kEs3xcH1WbrAr468MFe2A@mail.gmail.com>
Date:	Tue, 18 Nov 2014 17:50:19 +0530
From:	Vivek Gautam <gautamvivek1987@...il.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:	Vivek Gautam <gautam.vivek@...sung.com>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Greg KH <gregkh@...uxfoundation.org>, kishon <kishon@...com>,
	Felipe Balbi <balbi@...com>,
	Alan Stern <stern@...land.harvard.edu>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Julius Werner <jwerner@...gle.com>,
	Jingoo Han <jg1.han@...sung.com>
Subject: Re: [PATCH v7 1/2] usb: host: xhci-plat: Get PHYs for xhci's hcds

On Mon, Nov 17, 2014 at 9:46 PM, Sergei Shtylyov
<sergei.shtylyov@...entembedded.com> wrote:
> Hello.
>
> On 11/17/2014 9:36 AM, Vivek Gautam wrote:
>
>>>> The host controller by itself may sometimes need to handle PHY
>>>> and re-initialize it to re-configure some of the PHY parameters
>>>> to get full support out of the PHY controller.
>>>> Therefore, facilitate getting the two possible PHYs, viz.
>>>> USB 2.0 type (UTMI+) and USB 3.0 type (PIPE3), and initialize them.
>
>
>>>> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
>>>> ---
>>>>    drivers/usb/host/xhci-plat.c |   74
>>>> ++++++++++++++++++++++++++++++++++++++++++
>>>>    1 file changed, 74 insertions(+)
>
>
>>>> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
>>>> index 3d78b0c..5207d5b 100644
>>>> --- a/drivers/usb/host/xhci-plat.c
>>>> +++ b/drivers/usb/host/xhci-plat.c
>
> [...]
>>>>
>>>> @@ -204,6 +271,8 @@ static int xhci_plat_suspend(struct device *dev)
>>>>          struct usb_hcd  *hcd = dev_get_drvdata(dev);
>>>>          struct xhci_hcd *xhci = hcd_to_xhci(hcd);
>>>>
>>>> +       phy_exit(hcd->phy);
>
>
>>>     Hm, in the suspend() method?
>
>
>> phy_exit() should eventually be suspending the PHY and put it to
>> low power state.
>
>
>    I thought it's a role that the power_off() mothod should play,
> considering that the power_on() method gets called after the init()
> method....

phy_power_off() should be cutting the clocks and power from PHY
completely, no ?
In that case one may not be able to wakeup the system from USB.

So phy_exit() gets the responsibility to put the PHY into low power state.

Ccing Kishon also to get his opinion on actual role of the two callbacks -
phy_init/exit() and phy_power_on/off().

>
>> phy_init() in resume() will then take up the task of activating the
>> PHY again.
>
>
>> phy_power_on() and phy_power_off() are called at xhci_probe() and remove()
>> time.
>
>
>    Of course.
>
>> Does this makes sense ?
>
>
>    Not much, really.
>
> WBR, Sergei
>



-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India
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