linux-kernel - Re: [PATCH v2 3/4] usb: host: xhci-plat: Caibrate PHY post host reset

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Date:	Fri, 11 Jul 2014 09:18:16 +0530
From:	Vivek Gautam <gautam.vivek@...sung.com>
To:	Julius Werner <jwerner@...omium.org>
Cc:	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	kishon <kishon@...com>, Kukjin Kim <kgene.kim@...sung.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Pratyush Anand <pratyush.anand@...com>
Subject: Re: [PATCH v2 3/4] usb: host: xhci-plat: Caibrate PHY post host reset

On Wed, Jul 9, 2014 at 11:28 PM, Julius Werner <jwerner@...omium.org> wrote:
> On Wed, Jul 9, 2014 at 3:01 AM, Vivek Gautam <gautam.vivek@...sung.com> wrote:
>> Some quirky PHYs may require to be calibrated post the host
>> controller initialization.
>> The USB 3.0 DRD PHY on Exynos5420/5800 systems, coming along with
>> Synopsys's DWC3 controller, is one such PHY which needs to be
>> calibrated post xhci's reset at initialization time and at
>> resume time, to get the controller work at SuperSpeed.
>>
>> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
>> ---
>>  drivers/usb/host/xhci-plat.c |   39 +++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 37 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
>> index e50bd7d..decf349 100644
>> --- a/drivers/usb/host/xhci-plat.c
>> +++ b/drivers/usb/host/xhci-plat.c
>> @@ -35,7 +35,27 @@ static void xhci_plat_quirks(struct device *dev, struct xhci_hcd *xhci)
>>  /* called during probe() after chip reset completes */
>>  static int xhci_plat_setup(struct usb_hcd *hcd)
>>  {
>> -       return xhci_gen_setup(hcd, xhci_plat_quirks);
>> +       struct device *parent;
>> +       int ret;
>> +
>> +       ret = xhci_gen_setup(hcd, xhci_plat_quirks);
>> +       if (ret) {
>> +               dev_err(hcd->self.controller, "xhci setup failed\n");
>> +               return ret;
>> +       }
>> +
>> +       parent = hcd->self.controller->parent;
>> +       if (of_device_is_compatible(parent->of_node, "synopsys,dwc3") ||
>> +           of_device_is_compatible(parent->of_node, "snps,dwc3")) {
>> +               if (!IS_ERR(hcd->gen_phy)) {
>> +                       ret = phy_calibrate(hcd->gen_phy);
>> +                       if (ret < 0 && ret != -ENOTSUPP)
>> +                               dev_err(hcd->self.controller,
>> +                                       "failed to calibrate USB PHY\n");
>> +               }
>> +       }
>
> Here as well, is it really necessary to special-case it so much? I'd
> say if there is a PHY and it has a calibrate function bound we call
> it, and if not we just go ahead.
>
> I also think that this would fit better in core/hcd.c since it's not
> really XHCI specific... it's conceivable that an EHCI controller might
> also need to tune some PHY settings after reset (in fact Tegra does
> something similar, although it already has another hack for that now),
> so if we introduce this general facility why not offer it to
> everyone?.

True, lets move it to core/hcd.c to make the entire calibration thing
more generic.

>
>> +
>> +       return ret;
>>  }
>>
>>  static int xhci_plat_start(struct usb_hcd *hcd)
>> @@ -288,8 +308,23 @@ static int xhci_plat_resume(struct device *dev)
>>  {
>>         struct usb_hcd  *hcd = dev_get_drvdata(dev);
>>         struct xhci_hcd *xhci = hcd_to_xhci(hcd);
>> +       int ret;
>> +
>> +       ret = xhci_resume(xhci, 0);
>> +       if (ret)
>> +               return ret;
>>
>> -       return xhci_resume(xhci, 0);
>> +       if (of_device_is_compatible(dev->parent->of_node, "synopsys,dwc3") ||
>> +           of_device_is_compatible(dev->parent->of_node, "snps,dwc3")) {
>> +               if (!IS_ERR(hcd->gen_phy)) {
>> +                       ret = phy_calibrate(hcd->gen_phy);
>> +                       if (ret < 0 && ret != -ENOTSUPP)
>> +                               dev_err(hcd->self.controller,
>> +                                       "failed to calibrate USB PHY\n");
>> +               }
>> +       }
>> +
>> +       return ret;
>>  }
>>
>>  static const struct dev_pm_ops xhci_plat_pm_ops = {
>> --
>> 1.7.10.4
>>
> --
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-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India
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