linux-kernel - Re: [PATCH v4 02/13] dt-bindings: Add bindings for peci-aspeed

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Date:   Tue, 7 Dec 2021 18:15:11 +0000
From:   "Winiarska, Iwona" <iwona.winiarska@...el.com>
To:     "billy_tsai@...eedtech.com" <billy_tsai@...eedtech.com>,
        "zweiss@...inix.com" <zweiss@...inix.com>
CC:     "corbet@....net" <corbet@....net>,
        "jae.hyun.yoo@...ux.intel.com" <jae.hyun.yoo@...ux.intel.com>,
        "robh@...nel.org" <robh@...nel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "andrew@...id.au" <andrew@...id.au>,
        "jdelvare@...e.com" <jdelvare@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "olof@...om.net" <olof@...om.net>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux@...ck-us.net" <linux@...ck-us.net>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "bp@...en8.de" <bp@...en8.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "pierre-louis.bossart@...ux.intel.com" 
        <pierre-louis.bossart@...ux.intel.com>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 02/13] dt-bindings: Add bindings for peci-aspeed

On Thu, 2021-12-02 at 02:31 +0000, Billy Tsai wrote:
> Hi Zev,
> 
> On 2021/12/2, 9:55 AM, "Zev Weiss" <zweiss@...inix.com> wrote:
> 
>     On Wed, Dec 01, 2021 at 02:38:04AM PST, Billy Tsai wrote:
>     >   >Hi,
>     >   >
>     >   >On 2021/11/23, 10:10 PM, "openbmc on behalf of Iwona Winiarska"
> <openbmc-bounces+billy_tsai=aspeedtech.com@...ts.ozlabs.org on behalf of
> iwona.winiarska@...el.com> wrote:
>     >   >
>     >   >    Add device tree bindings for the peci-aspeed controller driver.
>     >   >
>     >   >    >   +  aspeed,clock-divider:
>     >   >    >   +    description:
>     >   >    >   +      This value determines PECI controller internal clock
> dividing
>     >   >    >   +      rate. The divider will be calculated as 2 raised to
> the power of
>     >   >    >   +      the given value.
>     >   >    >   +    $ref: /schemas/types.yaml#/definitions/uint32
>     >   >    >   +    minimum: 0
>     >   >    >   +    maximum: 7
>     >   >    >   +    default: 0
>     >   >    >   +
>     >   >    >   +  aspeed,msg-timing:
>     >   >    >   +    description:
>     >   >    >   +      Message timing negotiation period. This value will
> determine the period
>     >   >    >   +      of message timing negotiation to be issued by PECI
> controller. The unit
>     >   >    >   +      of the programmed value is four times of PECI clock
> period.
>     >   >    >   +    $ref: /schemas/types.yaml#/definitions/uint32
>     >   >    >   +    minimum: 0
>     >   >    >   +    maximum: 255
>     >   >    >   +    default: 1
>     >   >    >   +
>     >   >    >   +  aspeed,addr-timing:
>     >   >    >   +    description:
>     >   >    >   +      Address timing negotiation period. This value will
> determine the period
>     >   >    >   +      of address timing negotiation to be issued by PECI
> controller. The unit
>     >   >    >   +      of the programmed value is four times of PECI clock
> period.
>     >   >    >   +    $ref: /schemas/types.yaml#/definitions/uint32
>     >   >    >   +    minimum: 0
>     >   >    >   +    maximum: 255
>     >   >    >   +    default: 1
>     >   >I suggest deleting these three properties and replacing them with the
> following
>     >   >
>     >   >aspeed,peci-bit-time:
>     >   >        description:
>     >   >          The bit time driven by PECI controller. The unit of the
> value is Hz.
>     >   >    minimum: 2000
>     >   >    maximum: 1000000
>     >   >
>     >   >And the driver should use this property to caculate the appropriate
> clock-divider,
>     >   >msg-timing and addr-timing, instead of exposing hardware registers to
> dts.
>     >   >
> 
>     >   Or perhaps just 'bus-frequency' a la i2c-aspeed, gpio-aspeed-sgpio,
> etc?
> 
> It's a good ideal for the consistency.

If we want to go with passing frequency - I would prefer to go with "clock-
frequency" and use clock framework for exposing it to peci-aspeed (as I
mentioned in reply to patch 05).

What do you think?

Thanks
-Iwona

> 
> Thanks
> 
> Best Regards,
> Billy Tsai
> 
>