linux-kernel - Re: [PATCH -next 1/2] i2c: designware: Switch from using MMIO access to SMN access

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Date:   Thu, 22 Sep 2022 16:29:53 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Borislav Petkov <bp@...e.de>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Limonciello, Mario" <mario.limonciello@....com>,
        Jan Dąbroś <jsd@...ihalf.com>,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        jarkko.nikula@...ux.intel.com, wsa@...nel.org,
        rrangel@...omium.org, upstream@...ihalf.com,
        Muralidhara M K <muralimk@....com>,
        Naveen Krishna Chatradhi <nchatrad@....com>
Subject: Re: [PATCH -next 1/2] i2c: designware: Switch from using MMIO access
 to SMN access

Hi,

On 9/22/22 16:04, Borislav Petkov wrote:
> On Thu, Sep 22, 2022 at 03:48:07PM +0200, Hans de Goede wrote:
>> Right, thank you for Cc-ing me. At least on X86 there are several platforms
>> (and 100-s of device models) which use a PMIC connected to the i2c-designware
>> controller and this PMIC gets poked directly from ACPI _S0 and _S3
>> (power on/off) methods. So the I2C bus driver needs to *bind* to the controller
>> as soon as we find its description in ACPI, otherwise we get a whole bunch
>> of failed ACPI OpRegion access errors as well as various actual really issues.
> 
> Thanks for explaining - I couldn't find the reason why it has to be a
> subsys_initcall.
> 
>> So please keep this as a subsys initcall.
> 
> Which means, init_amd_nbs() would have to be sorted to run before
> dw_i2c_init_driver()...

Yes if possible. One solution might be to make it a arch_initcall_sync()
which AFAIK runs after regular arch_initcall()-s but before subsys_initcall()-s.

Regards,

Hans