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

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Message-ID: <YmHiofjPdWux1BJ6@lunn.ch>
Date:   Fri, 22 Apr 2022 01:02:57 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Sean Anderson <sean.anderson@...o.com>
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

On Thu, Apr 21, 2022 at 06:06:39PM -0400, Sean Anderson wrote:
> 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.

Ah, so -supply means regulator. I would spell it out for dumb people
like my:

  ta-prog-sfp-supply:
    description:
      The regulator supplying TA_PROG_SFP. It will be enabled for programming and disabled
      for reading.

      Andrew