linux-kernel - RE: [PATCH v4 3/3] i2c: aspeed: support ast2600 i2c new register mode driver

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Date:   Tue, 14 Feb 2023 08:57:02 +0000
From:   Ryan Chen <ryan_chen@...eedtech.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Jeremy Kerr <jk@...abs.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v4 3/3] i2c: aspeed: support ast2600 i2c new register mode
 driver

Hello Krzysztof,

> 
> On 14/02/2023 07:12, Ryan Chen wrote:
> > Hello Krzysztof,
> >>
> >>> On 02/02/2023 10:16, Ryan Chen wrote:
> >>>>>>> +static struct platform_driver ast2600_i2c_global_driver = {
> >>>>>> +       .probe  = ast2600_i2c_global_probe,
> >>>>>> +       .driver = {
> >>>>>> +               .name = KBUILD_MODNAME,
> >>>>>> +               .of_match_table =
> >> ast2600_i2c_global_of_match,
> >>>>>> +       },
> >>>>>> +};
> >>>>>> +
> >>>>>> +static int __init ast2600_i2c_global_init(void) {
> >>>>>> +       return
> >>>>>> +platform_driver_register(&ast2600_i2c_global_driver);
> >>>>>> +}
> >>>>>> +device_initcall(ast2600_i2c_global_init);
> >>>>>
> >>>>> Maybe module_platform_driver() instead?
> >>>>
> >>>> Due to i2c global is top of all i2c bus like the scu, it make sure
> >>>> the driver is
> >>> before the i2c bus driver probe.
> >>>> It is needed use device_initcal function.
> >>>
> >>> No, we do not do such ordering. device links and proper resource
> >>> sharing handle the order. This must be module_platform_driver()
> >>> (assuming we do not drop entire submission).
> >>
> >>
> >> If global driver use module_platform_driver, does i2c driver will
> >> latter the global driver probe?
> >> If yes, I think it will workable.
> >>>
> > I find a good way instead.
> > subsys_initcall(ast2600_i2c_global_init); is better ?
> 
> Not really, this is not a subsystem. This is module platform driver so use it.
> 
But, I need i2c-global to be early then i2c-ast2600 driver. The subsys_initcall is needed.
I2c-global driver to initial full i2c clock and reset, after this, i2c bus driver(i2c-ast2600.c) can work. 
So I suggest to use subsys_initcall in i2c global driver. Is it ok?
Best regards,