linux-kernel - Re: [PATCH v2 14/20] mfd: intel_soc_pmic_chtwc: Add intel_cht_wc_get

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Date:   Tue, 16 Nov 2021 13:18:05 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Hans de Goede <hdegoede@...hat.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>,
        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-i2c <linux-i2c@...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 v2 14/20] mfd: intel_soc_pmic_chtwc: Add
 intel_cht_wc_get_model() helper function

On Sun, Nov 14, 2021 at 7:04 PM 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

does not

> 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 helper function for this
> and make this id 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.

...

> +               /*
> +                * Note this may not seem like a very unique match, but in the
> +                * 24000+ DMI decode dumps from linux-hardware.org only 42 have

Can you add https:// (or is it gopher? :)

> +                * a board_vendor value of "AMI Corporation" and of those 42
> +                * only 1 (the GPD win/pocket entry) has a board_name of
> +                * "Default string". Also very few devices have both board_ and
> +                * product_name not set.
> +                */

...

> +enum intel_cht_wc_models intel_cht_wc_get_model(void)
> +{
> +       const struct dmi_system_id *id;
> +
> +       id = dmi_first_match(cht_wc_model_dmi_ids);
> +       if (!id)
> +               return INTEL_CHT_WC_UNKNOWN;
> +
> +       return (long)id->driver_data;

Why not proper casting, i.e. (enum intel_...)?

> +}
> +EXPORT_SYMBOL_GPL(intel_cht_wc_get_model);

Are you planning to use EXPORT_SYMBOL_GPL_NS()? If not, please consider it.

-- 
With Best Regards,
Andy Shevchenko