linux-kernel - Re: [PATCH] regulator: core: Fix off-on-delay-us for always-on/boot-on regulators

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Message-Id: <2B145293-BAAE-40AE-B408-FCFC4A80E46D@kohlschutter.com>
Date:   Sun, 17 Jul 2022 13:39:24 +0200
From:   Christian Kohlschütter 
        <christian@...lschutter.com>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] regulator: core: Fix off-on-delay-us for
 always-on/boot-on regulators

This is _somewhat_ related to "[PATCH] regulator: core: Fix off-on-delay-us for always-on/boot-on regulators"
That other patch is the right solution for my specific problem, and no further fixes are necessary.

This change fixes an attempted "bandage" solution (adding an "off-on-delay-us") that we had initially tried to no avail.
While the cleanup not only reduces complexity, it may also prevent future code changes reintroducing the non-delayed cycling after registration.

from arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi:
vcc3v0_sd: vcc3v0-sd {
        compatible = "regulator-fixed";
        enable-active-high;
        gpio = <&gpio0 RK_PA1 GPIO_ACTIVE_HIGH>;
        pinctrl-names = "default";
        pinctrl-0 = <&sdmmc0_pwr_h>;
        regulator-always-on; // prevents setting last_off upon registration
        off-on-delay-us = <500000>; // would not be honored upon regulator_register
        regulator-min-microvolt = <3000000>;
        regulator-max-microvolt = <3000000>;
        regulator-name = "vcc3v0_sd";
        vin-supply = <&vcc3v3_sys>;
};

> Am 17.07.2022 um 13:30 schrieb Christian Kohlschuetter <christian@...lschuetter.com>:
> 
> Regulators marked with "regulator-always-on" or "regulator-boot-on"
> as well as an "off-on-delay-us", may run into cycling issues that are
> hard to detect.
> 
> This is caused by the "last_off" state not being initialized in this
> case.
> 
> Fix the "last_off" initialization by setting it to the current kernel
> time upon initialization, regardless of always_on/boot_on state.
> 
> Signed-off-by: Christian Kohlschütter <christian@...lschutter.com>
> ---
> drivers/regulator/core.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
> index c4d844ffad7a..48ed33ad48c8 100644
> --- a/drivers/regulator/core.c
> +++ b/drivers/regulator/core.c
> @@ -1522,6 +1522,9 @@ static int set_machine_constraints(struct regulator_dev *rdev)
> 		}
> 	}
> 
> +	if (rdev->desc->off_on_delay)
> +		rdev->last_off = ktime_get();
> +
> 	/* If the constraints say the regulator should be on at this point
> 	 * and we have control then make sure it is enabled.
> 	 */
> @@ -1549,8 +1552,6 @@ static int set_machine_constraints(struct regulator_dev *rdev)
> 
> 		if (rdev->constraints->always_on)
> 			rdev->use_count++;
> -	} else if (rdev->desc->off_on_delay) {
> -		rdev->last_off = ktime_get();
> 	}
> 
> 	print_constraints(rdev);
> -- 
> 2.36.1
> 
> 



-- 
Dr. Christian Kohlschütter