linux-kernel - Re: [PATCH v6 2/2] dt-bindings: mfd: Add DT compatible string "google,cros_ec

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Date:   Sun, 11 Oct 2020 19:11:17 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Duncan Laurie <dlaurie@...gle.com>
Cc:     Bhanu Prakash Maiya <bhanumaiya@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Raul E Rangel <rrangel@...omium.org>,
        devicetree@...r.kernel.org, Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        Eric Peers <epeers@...gle.com>,
        Furquan Shaikh <furquan@...omium.org>,
        Lee Jones <lee.jones@...aro.org>, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v6 2/2] dt-bindings: mfd: Add DT compatible string
 "google,cros_ec_uart"

Hi Duncan,

On 11/10/20 18:35, Duncan Laurie wrote:
> On Sun, Oct 11, 2020 at 4:59 AM Enric Balletbo i Serra
> <enric.balletbo@...labora.com <mailto:enric.balletbo@...labora.com>> wrote:
> 
>     Hi Bhanu,
> 
>     Thank you for your patch.
> 
>     On 9/10/20 23:01, Bhanu Prakash Maiya wrote:
>     > Add DT compatible string in
>     > Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
>     >
> 
>     The problem with this patchset continues being the same. You are using the trick
>     of using a DT compatible string to instantiate an ACPI-only driver. You should
>     have an ACPI ID for that device or use a DMI table to match the device and
>     instantiate it (see for example the platform/chrome/cros_ec_lpc.c).
> 
> 
> 
> It isn't really meant to be an ACPI only driver, it just happens to be an x86
> system that uses the UART interface first.  We use this PRP0001 instantiation
> method with a lot of different drivers like MIPI cameras, fingerprint sensors,
> the cr50 TPM driver, etc.
> 

Right, but then you need to define a proper DT binding, with all the options,
not only the compatible name.

> That said it is true that the rest of the cros_ec drivers use distinct ACPI
> IDs.  Bhanu I allocated GOOG0019 for the cros_ec UART interface so you can
> switch to using that instead.  You'll need to update the coreboot interface as
> well and might want to keep both devices in firmware to ease the transition.
> 

Thank you.

  Enric

> -duncan
> 
>  
> 
> 
>     > Signed-off-by: Bhanu Prakash Maiya <bhanumaiya@...omium.org
>     <mailto:bhanumaiya@...omium.org>>
>     > Reviewed-by: Rob Herring <robh@...nel.org <mailto:robh@...nel.org>>
>     > ---
>     >
>     > Changes in v6:
>     > - No change
>     >
>     > Changes in v5:
>     > - No change
>     >
>     > Changes in v4:
>     > - Changes in commit message.
>     >
>     > Changes in v3:
>     > - Rebased changes on google,cros-ec.yaml
>     >
>     > Changes in v2:
>     > - No change
>     >
>     >  Documentation/devicetree/bindings/mfd/google,cros-ec.yaml | 6 +++++-
>     >  1 file changed, 5 insertions(+), 1 deletion(-)
>     >
>     > diff --git a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
>     b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
>     > index 6a7279a85ec1c..552d1c9bf3de4 100644
>     > --- a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
>     > +++ b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
>     > @@ -10,11 +10,12 @@ maintainers:
>     >    - Benson Leung <bleung@...omium.org <mailto:bleung@...omium.org>>
>     >    - Enric Balletbo i Serra <enric.balletbo@...labora.com
>     <mailto:enric.balletbo@...labora.com>>
>     >    - Guenter Roeck <groeck@...omium.org <mailto:groeck@...omium.org>>
>     > +  - Bhanu Prakash Maiya <bhanumaiya@...omium.org
>     <mailto:bhanumaiya@...omium.org>>
>     > 
>     >  description:
>     >    Google's ChromeOS EC is a microcontroller which talks to the AP and
>     >    implements various functions such as keyboard and battery charging.
>     > -  The EC can be connected through various interfaces (I2C, SPI, and others)
>     > +  The EC can be connected through various interfaces (I2C, SPI, UART and
>     others)
>     >    and the compatible string specifies which interface is being used.
>     > 
>     >  properties:
>     > @@ -29,6 +30,9 @@ properties:
>     >        - description:
>     >            For implementations of the EC is connected through RPMSG.
>     >          const: google,cros-ec-rpmsg
>     > +      - description:
>     > +          For implementations of the EC is connected through UART.
>     > +        const: google,cros-ec-uart
>     > 
>     >    google,cros-ec-spi-pre-delay:
>     >      description:
>     >
>