linux-kernel - Re: [PATCH v2] mfd: axp20x: Update AXP288 volatile ranges

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Date:   Wed, 30 Jun 2021 23:22:29 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Lee Jones <lee.jones@...aro.org>, linux-acpi@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Clamshell <clamfly@....com>
Subject: Re: [PATCH v2] mfd: axp20x: Update AXP288 volatile ranges

On Wed, Jun 30, 2021 at 1:12 AM Hans de Goede <hdegoede@...hat.com> wrote:
>
> On Cherry Trail devices with an AXP288 PMIC the external SD-card slot
> used the AXP's DLDO2 as card-voltage and either DLDO3 or GPIO1LDO
> (GPIO1 pin in low noise LDO mode) as signal-voltage.
>
> These regulators are turned on/off and in case of the signal-voltage
> also have their output-voltage changed by the _PS0 and _PS3 power-
> management ACPI methods on the MMC-controllers ACPI fwnode as well as
> by the _DSM ACPI method for changing the signal voltage.
>
> The AML code implementing these methods is directly accessing the
> PMIC through ACPI I2C OpRegion accesses, instead of using the special
> PMIC OpRegion handled by drivers/acpi/pmic/intel_pmic_xpower.c .
>
> This means that the contents of the involved PMIC registers can change
> without the change being made through the regmap interface, so regmap
> should not cache the contents of these registers.
>
> Mark the regulator power on/off, the regulator voltage control and the
> GPIO1 control registers as volatile, to avoid regmap caching them.
>
> Specifically this fixes an issue on some models where the i915 driver
> toggles another LDO using the same on/off register on/off through
> MIPI sequences (through intel_soc_pmic_exec_mipi_pmic_seq_element())
> which then writes back a cached on/off register-value where the
> card-voltage is off causing the external sdcard slot to stop working
> when the screen goes blank, or comes back on again.
>
> The regulator register-range now marked volatile also includes the
> buck regulator control registers. This is done on purpose these are
> normally not touched by the AML code, but they are updated directly
> by the SoC's PUNIT which means that they may also change without going
> through regmap.
>
> Note the AXP288 PMIC is only used on Bay- and Cherry-Trail platforms,
> so even though this is an ACPI specific problem there is no need to
> make the new volatile ranges conditional since these platforms always
> use ACPI.
>
> Fixes: dc91c3b6fe66 ("mfd: axp20x: Mark AXP20X_VBUS_IPSOUT_MGMT as volatile")
> Fixes: cd53216625a0 ("mfd: axp20x: Fix axp288 volatile ranges")
> Reported-and-tested-by: Clamshell <clamfly@....com>
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>

Reviewed-by: Chen-Yu Tsai <wens@...e.org>