linux-kernel - Re: [PATCH v15 3/8] mfd: simple-mfd-i2c: Enable support for the silergy,sy7636a

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Date:   Wed, 24 Nov 2021 20:35:32 +0100
From:   Andreas Kemnade <andreas@...nade.info>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Alistair Francis <alistair23@...il.com>,
        Alistair Francis <alistair@...stair23.me>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>, lgirdwood@...il.com,
        Rob Herring <robh+dt@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        rui.zhang@...el.com, devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        linux-hwmon@...r.kernel.org, amitk@...nel.org,
        linux-pm@...r.kernel.org, dl-linux-imx <linux-imx@....com>,
        Shawn Guo <shawnguo@...nel.org>
Subject: Re: [PATCH v15 3/8] mfd: simple-mfd-i2c: Enable support for the
 silergy,sy7636a

Hi,

On Tue, 23 Nov 2021 07:39:05 -0800
Guenter Roeck <linux@...ck-us.net> wrote:

> On 11/23/21 4:14 AM, Alistair Francis wrote:
> > On Tue, Nov 16, 2021 at 9:10 AM Andreas Kemnade <andreas@...nade.info> wrote:  
> >>
> >> Hi,
> >>
> >> this all creates a lot of question marks...
> >> One of my main question is whether sy7636a = sy7636 (at least the
> >> driver in the kobo vendor kernels does not have the "A" at the end,
> >> whic does not necessarily mean a difference).
> >>
> >> https://www.silergy.com/products/panel_pmic
> >> lists only a SY7636ARMC, so chances are good that the letters were just
> >> stripped away by the driver developers. Printing on chip package is
> >> cryptic so it is not that helpful. It is just "BWNBDA"  
> > 
> > I don't have a definite answer for you. But I think it's sy7636a
> > 
> > The page you linked to above lists SY7636ARMC as well as SY7627RMC,
> > SY7570RMC. That makes me think that the RMC is a generic suffix and
> > this actual IC is the SY7636A.
> >   
> 
> Almost all chips have an ordering suffix, indicating things like
> temperature range or packaging. The datasheet says:
> 
yes, they have. The only question is where it starts. So did you find a
public datasheet which you can chere

> Ordering Information
> SY7636 □(□□)□
>              | Temperature Code (C)
>           | Package Code (RM)
>         | Optional Spec Code (A)
> 
> The datasheet otherwise refers to the chip as SY7636A.
> 
so there is no indication of something like this where the A really
makes a difference:

commit 28e64a68a2ef1c48f30e8b6803725199929069fc
Author: Daniel Jeong <gshark.jeong@...il.com>
Date:   Tue Nov 12 15:08:58 2013 -0800

    backlight: lm3630: apply chip revision
    
    The LM3630 chip was revised by TI and chip name was also changed to
    LM3630A.  And register map, default values and initial sequences are
    changed.  The files, lm3630_bl.{c,h} are replaced by lm3630a_bl.{c,h} You
    can find more information about LM3630A(datasheet, evm etc) at
    http://www.ti.com/product/lm3630a

That is good to know. Thanks for your investigation. 

Regards,
Andreas