linux-kernel - RE: [PATCH] usb: tegra: Removing dependency on PHY instance number

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Message-ID: <D958900912E20642BCBC71664EFECE3E6E1A40D477@BGMAIL02.nvidia.com>
Date:	Mon, 24 Dec 2012 10:02:05 +0530
From:	Venu Byravarasu <vbyravarasu@...dia.com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"balbi@...com" <balbi@...com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] usb: tegra: Removing dependency on PHY instance number

> -----Original Message-----
> From: Stephen Warren [mailto:swarren@...dotorg.org]
> Sent: Saturday, December 22, 2012 2:32 AM
> To: Venu Byravarasu
> Cc: stern@...land.harvard.edu; gregkh@...uxfoundation.org;
> balbi@...com; linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] usb: tegra: Removing dependency on PHY instance
> number
> 
> On 12/20/2012 11:58 PM, Venu Byravarasu wrote:
> > Tegra2 has two varieties of USB PHYs:
> > Instance 0 - legacy PHY interface and
> > Instace 1 & 2 - non-legacy standard PHY interfaces.
> >
> > PHY driver is using instance numbers to identify the
> > interface type.
> >
> > With this patch Modified PHY driver to make use of
> > DT property for handling this.
> >
> > ULPI PHY is used on USB PHY instance 1 & UTMI is
> > used on other two instances. Hence modified PHY type
> > detection also from instance number to the parameter
> > passed from host driver.
> 
> Mostly seems fine to me; just a couple more things I noticed inline
> below. For the record, I'd like to take this through the Tegra tree with
> all the other Tegra-related USB patches in order to manage any
> dependencies, with the USB maintainers' Acks. Thanks.
> 
> > diff --git a/drivers/usb/phy/tegra_usb_phy.c
> b/drivers/usb/phy/tegra_usb_phy.c
> 
> > +struct tegra_usb_phy *tegra_usb_phy_open(struct device *dev,
> > +	bool is_legacy_mode, void __iomem *regs, void *config,
> > +	enum tegra_usb_phy_mode phy_mode)
> 
> > +	u8 index = is_legacy_mode ? 0 : 2;
> 
> I know this looks slightly icky, but I discussed earlier with Venu that
> this will be replaced by reading all the parameters out of device tree,
> as soon as this code becomes a true driver. I think the patch for that
> is up next, or at most after a few more cleanup patches.

Thanks Stephen.
As we discussed already, I'll use DT params in upcoming patches.

> 
> > +	phy->is_ulpi_phy = config ? true : false;
> >
> >  	if (!phy->config) {
> > -		if (phy_is_ulpi(phy)) {
> > +		if (phy->is_ulpi_phy) {
> >  			pr_err("%s: ulpi phy configuration missing",
> __func__);
> >  			err = -EINVAL;
> >  			goto err0;
> 
> That check will never fire now, since phy->is_ulpi_phy is calculated
> based on whether phy->config is set. I think it's fine for now to rely
> on the EHCI driver correctly passing config or NULL, and hence you could
> simply delete some of this error-checking code. I imagine that when the
> PHY driver is reworked to be an actual device rather than a utility
> module, phy->is_ulpi_phy will be determined by the compatible value of
> the PHY node in device tree.
 
Correct, Stephen.
Will use DT param for determining the PHY type.
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