linux-kernel - Re: [PATCH 0/2] add regulator driver and mfd cell for Intel Cherry Trail Whiskey Cove PMIC

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Date:   Mon, 28 Oct 2019 18:28:59 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Mark Brown <broonie@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andrey Zhizhikin <andrey.z@...il.com>, lgirdwood@...il.com,
        lee.jones@...aro.org, linux-kernel@...r.kernel.org,
        Andrey Zhizhikin <andrey.zhizhikin@...ca-geosystems.com>
Subject: Re: [PATCH 0/2] add regulator driver and mfd cell for Intel Cherry
 Trail Whiskey Cove PMIC

On Mon, Oct 28, 2019 at 02:26:21PM +0100, Hans de Goede wrote:
> On 28-10-2019 13:45, Mark Brown wrote:
> > On Mon, Oct 28, 2019 at 02:41:46PM +0200, Adrian Hunter wrote:
> > > On 25/10/19 10:55 AM, Andy Shevchenko wrote:
> > 
> > > > Since it's about UHS/SD, Cc to Adrian as well.
> > 
> > > My only concern is that the driver might conflict with ACPI methods trying
> > > to do the same thing, e.g. there is one ACPI SDHC instance from GPDWin DSDT
> > > with code like this:
> 
> Oh, right that is a very good point.
> 
> > That's certainly what's idiomatic for ACPI (though machine specific
> > quirks are too!).  The safe thing to do would be to only register the
> > supply on systems where we know there's no ACPI method.
> 
> Right, so as I mentioned before Andrey told me about the evaluation
> board he is using I was aware of only 3 Cherry Trail devices using
> the Whiskey Cove PMIC. The GPD win, the GPD pocket and the Lenovo
> Yoga book. I've checked the DSDT of all 3 and all 3 of them offer
> voltage control through the Intel _DSM method for voltage control.
> 
> I've also actually tested this on the GPD win and 1.8V signalling
> works fine there without needing Andrey's patch.
> 
> So it seems that Andrey's patch should only be active on his
> dev-board, as actual production hardware ships with the _DSM method.
> 
> I believe that the best solution is for the Whiskey Cove MFD driver:
> drivers/mfd/intel_soc_pmic_chtwc.c
> 
> To only register the new cell on Andrey's evaluation board model
> (based in a DMI match I guess). Another option would be to do
> the DMI check in the regulator driver, but that would mean
> udev will needlessly modprobe the regulator driver on production
> hardware, so doing it in the MFD driver and not registering the cell
> seems best,

I'm wondering if we can upgrade DSDT to provide _DSM for Aero platform.

-- 
With Best Regards,
Andy Shevchenko