linux-kernel - Re: [PATCH 3/8] dt-bindings: nvmem: sfp: Add TA_PROG

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Date:   Thu, 21 Apr 2022 18:06:39 -0400
From:   Sean Anderson <sean.anderson@...o.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        Shawn Guo <shawnguo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Li Yang <leoyang.li@....com>, linux-kernel@...r.kernel.org,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH 3/8] dt-bindings: nvmem: sfp: Add TA_PROG_SFP supply

Hi Andrew,

On 4/21/22 5:59 PM, Andrew Lunn wrote:
> On Thu, Apr 21, 2022 at 01:56:52PM -0400, Sean Anderson wrote:
>> The TA_PROG_SFP supply must be enabled to program the fuses, and
>> disabled to read the fuses (such as at power-on-reset). On many boards,
>> this supply is controlled by a jumper. The user must manually insert or
>> remove it at the appropriate time in the programming process. However,
>> on other boards this supply is controlled by and FPGA or a GPIO. In
>> these cases, the driver can automatically enabled and disable it as
>> necessary.
>> 
>> Signed-off-by: Sean Anderson <sean.anderson@...o.com>
>> ---
>> 
>>  .../devicetree/bindings/nvmem/fsl,layerscape-sfp.yaml        | 5 +++++
>>  1 file changed, 5 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/nvmem/fsl,layerscape-sfp.yaml b/Documentation/devicetree/bindings/nvmem/fsl,layerscape-sfp.yaml
>> index 54086f50157d..e7d1232fcd41 100644
>> --- a/Documentation/devicetree/bindings/nvmem/fsl,layerscape-sfp.yaml
>> +++ b/Documentation/devicetree/bindings/nvmem/fsl,layerscape-sfp.yaml
>> @@ -32,6 +32,11 @@ properties:
>>    clock-names:
>>      const: sfp
>>  
>> +  ta-prog-sfp-supply:
>> +    description:
>> +      The TA_PROG_SFP supply. It will be enabled for programming and disabled
>> +      for reading.
>> +
> 
> Doesn't there need to be some indication what this is? Is it a GPIO,
> or maybe a regulator?

There is a pin on these processors named "TA_PROG_SFP". The supply here should
be for whatever regulator supplies that pin. So it could be a fixed-regulator
or perhaps a sub-node of the board's FPGA (no such node exists yet, but it
certainly could). There's a pattern property under
Documentation/devicetree/bindings/regulator/regulator.yaml for these sorts
of nodes.

--Sean