linux-kernel - Re: [PATCH 3/3] phy: ulpi: add driver for TI TUSB1210

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Date:	Fri, 23 Jan 2015 10:12:41 +0200
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Felipe Balbi <balbi@...com>
Cc:	Kishon Vijay Abraham I <kishon@...com>,
	Baolu Lu <baolu.lu@...ux.intel.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] phy: ulpi: add driver for TI TUSB1210

Hi,

On Thu, Jan 22, 2015 at 02:49:25PM -0600, Felipe Balbi wrote:
> On Wed, Jan 21, 2015 at 11:17:49AM +0200, Heikki Krogerus wrote:
> > > > +	/* Store initial eye diagram optimisation value */
> > > > +	ret = ulpi_read(ulpi, ULPI_EXT_VENDOR_SPECIFIC);
> > > 
> > > do they *all* use this register for eye diagram optimization or is this
> > > something that Intel decided to do ?
> > > 
> > > (sorry, don't know much about tusb1210 other than it sucks like hell :-)
> > 
> > All I know that somebody needs to save the value. The ones using this
> > PHY who don't need to save it can most likely live without the driver.
> 
> right, but what I mean is: is it mandatory that Eye diagram
> configuration be stored in *this* register? Or is it more like a scratch
> register which Intel just happens to be using for Eye diagram data ?

The eye diagram tuning is in that register. Here's the spec:
http://www.ti.com/lit/ds/symlink/tusb1210.pdf

I'll add definition for the register (which is colourfully named
"VENDOR_SPECIFIC2").

> > > > +	if (ret < 0)
> > > > +		return ret;
> > > > +
> > > > +	tusb->ctx[0] = ret;
> > > > +
> > > > +	tusb->phy = ulpi_phy_create(ulpi, &phy_ops);
> > > > +	if (IS_ERR(tusb->phy))
> > > > +		return PTR_ERR(tusb->phy);
> > > > +
> > > > +	tusb->ulpi = ulpi;
> > > > +
> > > > +	phy_set_drvdata(tusb->phy, tusb);
> > > > +	dev_set_drvdata(&ulpi->dev, tusb);
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static void tusb1210_remove(struct ulpi *ulpi)
> > > > +{
> > > > +	struct tusb1210 *tusb = dev_get_drvdata(&ulpi->dev);
> > > 
> > > completely unrelated to $subject, but we might want to have a
> > > ulpi_{set,get}_drvdata() at some point.
> > 
> > Makes sense.
> > 
> > > In fact, we might decide to add an entire ULPI bus, eventually, though
> > > I'm still considering if there's any benefit to that.
> > 
> > I don't think I understand this comment? ULPI bus is what I'm
> > introducing in this set (the first patch in it)?
> 
> I mean introducing a real struct bus ulpi_bus_type :-) With match,
> probe, remove, etc.

I'm already doing that. Please check the first patch in this set:
"phy: add bus for USB ULPI PHYs".


Cheers,

-- 
heikki
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