linux-kernel - Re: [PATCH v1 5/9] of: Add NVIDIA Tegra XHCI controller binding

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Date:	Wed, 25 Jun 2014 17:13:10 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Andrew Bresticker <abrestic@...omium.org>
CC:	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-usb@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Russell King <linux@....linux.org.uk>,
	Linus Walleij <linus.walleij@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Grant Likely <grant.likely@...aro.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Kishon Vijay Abraham I <kishon@...com>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v1 5/9] of: Add NVIDIA Tegra XHCI controller binding

On 06/25/2014 05:01 PM, Andrew Bresticker wrote:
> On Wed, Jun 25, 2014 at 2:52 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>> On 06/18/2014 12:16 AM, Andrew Bresticker wrote:
>>> Add device-tree binding documentation for the XHCI controller present
>>> on Tegra124 and later SoCs.
>>
>>> diff --git a/Documentation/devicetree/bindings/usb/nvidia,tegra124-xhci.txt b/Documentation/devicetree/bindings/usb/nvidia,tegra124-xhci.txt
>>
>>> +Required properties:
>>> +--------------------
>>
>>> + - clock-names: Must include the following entries:
>>> +    - xusb_host
>>> +    - xusb_falcon_src
>>> +    - xusb_ss
>>> +    - xusb_ss_src
>>> +    - xusb_hs_src
>>> +    - xusb_fs_src
>>> +    - pll_u_480m
>>> +    - clk_m
>>> +    - pll_e
>>
>>> + - reset-names: Must include the following entries:
>>> +   - xusb_host
>>> +   - xusb_ss
>>
>> Usually the CAR has a reset control for each clock. So, I would expect
>> as many entries in reset-names as in clock-names. Even if the SW doesn't
>> currently touch all the reset lines, we should make sure the binding
>> requires them to be present so that any DT will contain the entries if
>> they're ever needed in the future.
> 
> The xusb_{falcon,host,hs,fs,ss}_src clocks all share the same reset
> bit (143), so I can add a single entry for those.
> 
>> In the CAR documentation, I see "XUSB_DEV" as a clock/reset bit. Is that
>> missing from the list above?
> 
> This is used when XUSB is in device mode, which the driver does not
> support.  I can add those clocks here though if you want.

That'd be a good idea. That way, the DT doesn't have to change later.

>>> +Optional properties:
>>
>>> + - s1p05v-supply: 1.05V supply regulator.
>>> + - s1p8v-supply: 1.8V supply regulator.
>>> + - s3p3v-supply: 3.3V supply regulator.
>>
>> What are those supplies for? I would have expected any input to the SoC
>> to have a name that described its purpose, and the pins and DT
>> properties would be named to match.
> 
> I *think* this what they are from looking at the schematic, but I'll
> have to ask around:
>  - s1p05v: avddio_pex, dvddio_pex, and maybe avdd_pll_erefe
>  - s1p8v: avdd_pll_utmip
>  - s3p3v: avdd_usb, hvdd_pex, hvdd_pex_pll_e
> Should these be separated out as they are for PCIe?

Yes, I think they should be separated. I wonder if the supplies for PCIe
shouldn't have been added to the XUSB padctrl rather than PCIe node
though? It probably doesn't matter much either way.
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