Re: [PATCH 2/2] dt-bindings: phy: tegra-xusb-padctl: Add Tegra210 support

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 11/13/2015 10:58 AM, Andrew Bresticker wrote:
> On Fri, Nov 13, 2015 at 8:32 AM, Thierry Reding
> <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> On Wed, Nov 04, 2015 at 01:59:51PM -0700, Stephen Warren wrote:
>>> On 11/04/2015 10:11 AM, Thierry Reding wrote:
>>>> From: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
>>>>
>>>> Extend the binding to cover the set of feature found in Tegra210.
>>>
>>>> diff --git a/Documentation/devicetree/bindings/phy/nvidia,tegra-xusb-padctl.txt b/Documentation/devicetree/bindings/phy/nvidia,tegra-xusb-padctl.txt
>>>
>>>> +For Tegra210, the list of valid PHY nodes is given below:
>>>> +- utmi: utmi-0, utmi-1, utmi-2, utmi-3
>>>> +  - functions: "snps", "xusb", "uart"
>>>> +- hsic: hsic-0, hsic-1
>>>> +  - functions: "snps", "xusb"
>>>> +- pcie: pcie-0, pcie-1, pcie-2, pcie-3, pcie-4, pcie-5, pcie-6
>>>> +  - functions: "pcie-x1", "usb3-ss", "pcie-x4"
>>>> +- sata: sata-0
>>>> +  - functions: "usb3-ss", "sata"
>>>
>>> usb2-bias also needs to be present.
>>
>> I'm not sure about this. All of the driver code that I've looked deals
>> with the usb2-bias pad internally. As far as I can tell, this pad needs
>> to be configured to whatever any of the other pads is configured for. I
>> think that means if any of the UTMI pads is configured for XUSB then the
>> usb2-bias pad must also be configured for XUSB. Which would also imply
>> that if one of the UTMI pads is configured for XUSB, all of them must be
>> configured for XUSB.
>
> I was told by hardware engineers at NVIDIA that (at least on
> Tegra124/Tegra132) the usb2-bias pad must be configured in the
> XUSB_PADCTL register space if UTMI pad 0 is muxed to XUSB.  If UTMI
> pad 0 is muxed to SNPS, then the usb2-bias pad is configured in the
> USB register space (base 0x7d000000).  You may want to follow up
> internally to confirm this.  If it's true, that could make things here
> a bit nastier, especially if we want to support configurations where
> some pads are muxed to XUSB while others are muxed to SNPS.

Hmm. I've certainly successfully tested a configuration where UTMI pad 0 
was handled by the SNPS controller and other pads by the XUSB controller 
*and* where I set the usb2-bias "pad"'s muxing and configuration via the 
XUSB PADCTL module. In that case, I /had/ to configure usb2-bias via 
XUSB PADCTL or the other XUSB pads didn't work. However, perhaps that 
was because the XUSB controller driver probed before the SNPS driver; 
perhaps if they'd probed the other way around and the SNPS driver 
configured the bias pad, then everything would have worked without 
configuring the bias pad via XUSB PADCTL.

I suppose I'll have to start another internal thread to get the full 
details, and differentiate between "recommended" and "supported" and 
"must" vs. "can"/"should".