linux-kernel - Re: [PATCH v4 14/20] mfd: intel_soc_pmic_chtwc: Add cht_wc_model data to struct intel_soc

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Message-ID: <94738e2d-8b8d-08a0-be39-343ac275fa5f@redhat.com>
Date:   Mon, 6 Dec 2021 22:46:41 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Mark Gross <markgross@...nel.org>,
        Andy Shevchenko <andy@...radead.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Lee Jones <lee.jones@...aro.org>,
        Sebastian Reichel <sre@...nel.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Ard Biesheuvel <ardb@...nel.org>, Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Yauhen Kharuzhy <jekhor@...il.com>,
        Tsuchiya Yuto <kitakar@...il.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v4 14/20] mfd: intel_soc_pmic_chtwc: Add cht_wc_model data
 to struct intel_soc_pmic

Hi,

On 12/6/21 20:55, Andy Shevchenko wrote:
> On Mon, Dec 6, 2021 at 11:35 AM Hans de Goede <hdegoede@...hat.com> wrote:
>>
>> Tablet / laptop designs using an Intel Cherry Trail x86 main SoC with
>> an Intel Whiskey Cove PMIC do not use a single standard setup for
>> the charger, fuel-gauge and other chips surrounding the PMIC /
>> charging+data USB port.
>>
>> Unlike what is normal on x86 this diversity in designs is not handled
>> by the ACPI tables. On 2 of the 3 known designs there are no standard
>> (PNP0C0A) ACPI battery devices and on the 3th design the ACPI battery
>> device does not work under Linux due to it requiring non-standard
>> and undocumented ACPI behavior.
>>
>> So to make things work under Linux we use native charger and fuel-gauge
>> drivers on these devices, re-using the native drivers used on ARM boards
>> with the same charger / fuel-gauge ICs.
>>
>> This requires various MFD-cell drivers for the CHT-WC PMIC cells to
>> know which model they are exactly running on so that they can e.g.
>> instantiate an I2C-client for the right model charger-IC (the charger
>> is connected to an I2C-controller which is part of the PMIC).
>>
>> Rather then duplicating DMI-id matching to check which model we are
>> running on in each MFD-cell driver, add a check for this to the
>> shared drivers/mfd/intel_soc_pmic_chtwc.c code by using a
>> DMI table for all 3 known models:
>>
>> 1. The GPD Win and GPD Pocket mini-laptops, these are really 2 models
>> but the Pocket re-uses the GPD Win's design in a different housing:
>>
>> The WC PMIC is connected to a TI BQ24292i charger, paired with
>> a Maxim MAX17047 fuelgauge + a FUSB302 USB Type-C Controller +
>> a PI3USB30532 USB switch, for a fully functional Type-C port.
>>
>> 2. The Xiaomi Mi Pad 2:
>>
>> The WC PMIC is connected to a TI BQ25890 charger, paired with
>> a TI BQ27520 fuelgauge, using the TI BQ25890 for BC1.2 charger type
>> detection, for a USB-2 only Type-C port without PD.
>>
>> 3. The Lenovo Yoga Book YB1-X90 / Lenovo Yoga Book YB1-X91 series:
>>
>> The WC PMIC is connected to a TI BQ25892 charger, paired with
>> a TI BQ27542 fuelgauge, using the WC PMIC for BC1.2 charger type
>> detection and using the BQ25892's Mediatek Pump Express+ (1.0)
>> support to enable charging with up to 12V through a micro-USB port.
> 
> ...
> 
>> +enum intel_cht_wc_models {
>> +       INTEL_CHT_WC_UNKNOWN,
>> +       INTEL_CHT_WC_GPD_WIN_POCKET,
>> +       INTEL_CHT_WC_XIAOMI_MIPAD2,
>> +       INTEL_CHT_WC_LENOVO_YOGABOOK1,
>> +};
> 
> ...
> 
>> +       enum intel_cht_wc_models cht_wc_model;
> 
> I'm wondering what will you do when something similar will be needed
> for another PMIC?
> 
> I see possible solutions to eliminate additional churn:
> - make just one enum for all models (can be done now, can be renamed later)
> - make a union if we have such situation
> 
> because I wouldn't like to have another field for each possible
> variant of PMIC in the generic structure.
> 
> Hence the question, does it make sense to just name it (enum and
> member) less cht_wc oriented?

I agree that renaming these to make them generic makes sense if we get a
second user (which I doubt, but you never know). For now I would like to
keep this as is though, this is a big series and I would like to avoid
to respin it just for this and we can always rename this later.

If I need to do a v5 anyways though, then I'll do the rename for v5.

Regards,

Hans