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

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Message-ID: <0d3919c9-40e0-7343-0bbc-159984348216@redhat.com>
Date:   Fri, 25 Oct 2019 11:38:52 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andrey Zhizhikin <andrey.z@...il.com>
Cc:     lgirdwood@...il.com, broonie@...nel.org, 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

Hi,

On 25-10-2019 09:53, Andy Shevchenko wrote:
> On Thu, Oct 24, 2019 at 02:29:37PM +0000, Andrey Zhizhikin wrote:
>> This patchset introduces additional regulator driver for Intel Cherry
>> Trail Whiskey Cove PMIC. It also adds a cell in mfd driver for this
>> PMIC, which is used to instantiate this regulator.
>>
>> Regulator support for this PMIC was present in kernel release from Intel
>> targeted Aero platform, but was not entirely ported upstream and has
>> been omitted in mainline kernel releases. Consecutively, absence of
>> regulator caused the SD Card interface not to be provided with Vqcc
>> voltage source needed to operate with UHS-I cards.
>>
>> Following patches are addessing this issue and making sd card interface
>> to be fully operable with UHS-I cards. Regulator driver lists an ACPI id
>> of the SD Card interface in consumers and exposes optional "vqmmc"
>> voltage source, which mmc driver uses to switch signalling voltages
>> between 1.8V and 3.3V.
>>
>> This set contains of 2 patches: one is implementing the regulator driver
>> (based on a non upstreamed version from Intel Aero), and another patch
>> registers this driver as mfd cell in exising Whiskey Cove PMIC driver.
> 
> Thank you.
> Hans, Cc'ed, has quite interested in these kind of patches.
> Am I right, Hans?

Yes since I do a lot of work on Bay and Cherry Trail hw enablement I'm
always interested in CHT specific patches.

Overall this series looks good (from a high level view I did not
do a detailed review) but I wonder if we really want to export all the
regulators when we just need the vsdio one?

Most regulators are controlled by either the P-Unit inside the CHT SoC
or through ACPI OpRegion accesses.  Luckily the regulator subsys does not
expose a sysfs interface for users to directly poke regulators, but this will
still make it somewhat easier for users to poke regulators which they should
leave alone.

Note I'm not saying this is wrong, having support for all regulators in place
in case we need it in the future is also kinda nice. OTOH if we just need the
one now, maybe we should just support the one for now ?

Andy do you have an opinion on this?

Andrey, may I ask which device you are testing this on?

Anyways overall good work, thank you for doing this!

Regards,

Hans