linux-kernel - Re: [PATCH 2/4] dt-bindings: phy-rockchip-inno-usb2: add documentation for extcon and utmi-avalid properties.

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Date:   Wed, 15 Aug 2018 13:08:00 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     linux-kernel@...r.kernel.org, amstan@...omium.org,
        groeck@...gle.com, kieran.bingham@...asonboard.com,
        kernel@...labora.com, bleung@...omium.org,
        devicetree@...r.kernel.org, Frank Wang <frank.wang@...k-chips.com>,
        linux-rockchip@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/4] dt-bindings: phy-rockchip-inno-usb2: add
 documentation for extcon and utmi-avalid properties.

Hi Heiko,

On 15/08/18 12:29, Heiko Stuebner wrote:
> Hi Enric,
> 
> Am Mittwoch, 15. August 2018, 11:59:32 CEST schrieb Enric Balletbo i Serra:
>> Commit 98898f3bc83c8 ("phy: rockchip-inno-usb2: support otg-port for
>> rk3399") introduces two new properties. The extcon property is used to
>> detect the cable-state, and the rockchip,utmi-avalid is used to indicate
>> which register should be used to detect the vbus state.
>>
>> Document these properties in the documentation binding.
>>
>> Fixes: 98898f3bc83c8 ("phy: rockchip-inno-usb2: support otg-port for rk3399")
>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
>> ---
>>
>>  .../devicetree/bindings/phy/phy-rockchip-inno-usb2.txt         | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/phy/phy-rockchip-inno-usb2.txt b/Documentation/devicetree/bindings/phy/phy-rockchip-inno-usb2.txt
>> index 074a7b3b0425..2d4808d3920b 100644
>> --- a/Documentation/devicetree/bindings/phy/phy-rockchip-inno-usb2.txt
>> +++ b/Documentation/devicetree/bindings/phy/phy-rockchip-inno-usb2.txt
>> @@ -23,6 +23,7 @@ Optional properties:
>>  		 register files". When set driver will request its
>>  		 phandle as one companion-grf for some special SoCs
>>  		 (e.g RV1108).
>> + - extcon : phandle to the extcon device for the otg phy.
> 
> That should probably mention that this is the extcon providing the cable-state?

ack.

> 
> 
>>  Required nodes : a sub-node is required for each port the phy provides.
>>  		 The sub-node name is used to identify host or otg port,
>> @@ -45,6 +46,8 @@ Required properties (port (child) node):
>>  Optional properties:
>>   - phy-supply : phandle to a regulator that provides power to VBUS.
>>  		See ./phy-bindings.txt for details.
>> + - rockchip,utmi-avalid : boolean, use the avalid register to get vbus status.
>> +			  Otherwise, use the bvalid register.
> 
> Not having looked to deeply into the usb2 phy, this might raise questions
> on why this is a hardware-description? Is this needed when something is not
> connected on the board?

I asked myself the same question and even I thought in just remove that code.

After some investigation, though, I saw that the UTMI+ specification [1] has two
signals similar to ID signal (page 11), the AValid signal is used to indicate if
the session for an A-peripheral is valid and the BValid signal that is used to
indicate if the session for a B-peripheral is valid. I suppose that use of one
or the other matters in some cases, but AFAICT this is not used and I didn't see
any binding using it.

Maybe someone else can give us more clues on the importance or not of this property?

[1] https://www.nxp.com/docs/en/brochure/UTMI-PLUS-SPECIFICATION.pdf

Enric

> 
> 
> Heiko
> 
>