linux-kernel - Re: [PATCH v4 1/2] mfd: tps65219: Implement LOCK register handling for TPS65214

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Message-ID: <454220b7-81cc-4450-812c-06bfbe527ee2@ti.com>
Date: Wed, 12 Nov 2025 13:03:22 -0600
From: Andrew Davis <afd@...com>
To: "Kory Maincent (TI.com)" <kory.maincent@...tlin.com>, Aaro Koskinen
	<aaro.koskinen@....fi>, Andreas Kemnade <andreas@...nade.info>, Kevin Hilman
	<khilman@...libre.com>, Roger Quadros <rogerq@...nel.org>, Tony Lindgren
	<tony@...mide.com>, Lee Jones <lee@...nel.org>, Shree Ramamoorthy
	<s-ramamoorthy@...com>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
	<krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
CC: Bajjuri Praneeth <praneeth@...com>, Thomas Petazzoni
	<thomas.petazzoni@...tlin.com>, <linux-omap@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<stable@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] mfd: tps65219: Implement LOCK register handling
 for TPS65214

On 11/12/25 9:14 AM, Kory Maincent (TI.com) wrote:
> The TPS65214 PMIC variant has a LOCK_REG register that prevents writes to
> nearly all registers when locked. Unlock the registers at probe time and
> leave them unlocked permanently.
> 
> This approach is justified because:
> - Register locking is very uncommon in typical system operation
> - No code path is expected to lock the registers during runtime

Any other entity in the system that could re-lock these registers?
How about low power modes or other PM handling?

> - Adding a custom regmap write function would add overhead to every
>    register write, including voltage changes triggered by CPU OPP
>    transitions from the cpufreq governor which could happen quite
>    frequently
> 
> Cc: stable@...r.kernel.org
> Fixes: 7947219ab1a2d ("mfd: tps65219: Add support for TI TPS65214 PMIC")
> Signed-off-by: Kory Maincent (TI.com) <kory.maincent@...tlin.com>
> ---
> Changes in v4:
> - Move the registers unlock in the probe instead of a custom regmap write
>    operation.
> 
> Changes in v3:
> - Removed unused variable.
> 
> Changes in v2:
> - Setup a custom regmap_bus only for the TPS65214 instead of checking
>    the chip_id every time reg_write is called.
> ---
>   drivers/mfd/tps65219.c       | 7 +++++++
>   include/linux/mfd/tps65219.h | 2 ++
>   2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/mfd/tps65219.c b/drivers/mfd/tps65219.c
> index 65a952555218d..f1115c5585545 100644
> --- a/drivers/mfd/tps65219.c
> +++ b/drivers/mfd/tps65219.c
> @@ -498,6 +498,13 @@ static int tps65219_probe(struct i2c_client *client)
>   		return ret;
>   	}
>   
> +	if (chip_id == TPS65214) {
> +		ret = i2c_smbus_write_byte_data(client, TPS65214_REG_LOCK,
> +						TPS65214_LOCK_ACCESS_CMD);
> +		if (ret)
> +			return ret;

Might be good to print out some error message here, otherwise LGTM,

Reviewed-by: Andrew Davis <afd@...com>

> +	}
> +
>   	ret = devm_regmap_add_irq_chip(tps->dev, tps->regmap, client->irq,
>   				       IRQF_ONESHOT, 0, pmic->irq_chip,
>   				       &tps->irq_data);
> diff --git a/include/linux/mfd/tps65219.h b/include/linux/mfd/tps65219.h
> index 55234e771ba73..3abf937191d0c 100644
> --- a/include/linux/mfd/tps65219.h
> +++ b/include/linux/mfd/tps65219.h
> @@ -149,6 +149,8 @@ enum pmic_id {
>   #define TPS65215_ENABLE_LDO2_EN_MASK                    BIT(5)
>   #define TPS65214_ENABLE_LDO1_EN_MASK			BIT(5)
>   #define TPS65219_ENABLE_LDO4_EN_MASK			BIT(6)
> +/* Register Unlock */
> +#define TPS65214_LOCK_ACCESS_CMD			0x5a
>   /* power ON-OFF sequence slot */
>   #define TPS65219_BUCKS_LDOS_SEQUENCE_OFF_SLOT_MASK	GENMASK(3, 0)
>   #define TPS65219_BUCKS_LDOS_SEQUENCE_ON_SLOT_MASK	GENMASK(7, 4)
>