Re: [PATCH 1/2] phy: usbphy: Add dt documentation for Broadcom Cygnus USB PHY driver

From: Arun Ramamurthy
Date: Wed Feb 18 2015 - 19:45:33 EST

On 15-02-18 07:15 AM, Arnd Bergmann wrote:
On Tuesday 17 February 2015 13:05:50 Arun Ramamurthy wrote:
On 15-02-17 12:53 PM, Arnd Bergmann wrote:
On Tuesday 17 February 2015 12:00:49 Arun Ramamurthy wrote:
Arnd, I patched the ehci and ohci driver to accept multiple phys so they
require different names and cannot both be "usb". That patch was
accepted by Alen Stern but I did not update the bindings documentation.
I will send out another patch for that. Could we go with the naming
scheme of "usb" + "p" + port number or do you have other suggestions?

I don't have a good idea, but I think it would be best if the first
phy could remain named "usb" for compatibility with the existing binding.

The patch was written in a way that all the existing and new drivers can
continue to use "usb" if they are using only one phy so that we remain
compatible. The names need to be different only if more than one phy is
specified. In such cases i don't think the first phy should be "usb" as
it would be confusing to have
phy-names = "usb","usbp1"

I see your patch now, as 7e7a0e67f2c ("usb: ehci-platform: add support for
multiple phys per controller"), and I'm not too happy about the way you
did this.

We already concluded that there should have been a binding change
to go along with this, and that would have caught the fact that you
circumvent the API here by reading the phy names manually. That
part should never have made it into the kernel.

I think we can do this either by defining specific names for the
phy, or by changing the generic PHY binding to allow anonymous
phy references (leaving out "phy-names" entirely), and adding a
proper API for that.

Thanks Arnd, I will wait for Alan's comments before proceeding. I am happy to patch the ehci-platform driver to use a new api instead of devm_phy_get if that is the best option.

Should I run this by Alan Stern?

I've added him to Cc here. He clearly didn't know the background about
the DT binding change, and should not need to, but he may have an opinion
on what names we should use.

What is the reason for having two phys in your case? Are these
identical phy devices connected to a single controller or do they
server different purposes?

Yes, we have three identical phys connected to a single host controller
and one of the phys is also connected to the device controller

Ok, no problem with that, let's just make sure we come up with a
good binding for it.


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