linux-kernel - Re: [PATCH] regulator: pwm: Fix regulator ramp delay for continuous mode

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Message-ID: <57725238.9010809@gmail.com>
Date:	Tue, 28 Jun 2016 18:32:24 +0800
From:	Caesar Wang <caesar.upstream@...il.com>
To:	Douglas Anderson <dianders@...omium.org>,
	Mark Brown <broonie@...nel.org>
CC:	boris.brezillon@...e-electrons.com,
	Heiko Stuebner <heiko@...ech.de>, linux-kernel@...r.kernel.org,
	briannorris@...omium.org, lgirdwood@...il.com,
	linux-rockchip@...ts.infradead.org, lee.jones@...aro.org
Subject: Re: [PATCH] regulator: pwm: Fix regulator ramp delay for continuous
 mode


On 2016年06月28日 12:53, Douglas Anderson wrote:
> The original commit adding support for continuous voltage mode didn't
> handle the regulator ramp delay properly.  It treated the delay as a
> fixed delay in uS despite the property being defined as uV / uS.  Let's
> adjust it.  Luckily there appear to be no users of this ramp delay for
> PWM regulators (as per grepping through device trees in linuxnext).
>
> Note also that the upper bound of usleep_range probably shouldn't be a
> full 1 ms longer than the lower bound since I've seen plenty of hardware
> with a ramp rate of ~5000 uS / uV and for small jumps the total delays
> are in the tens of uS.  1000 is way too much.  We'll try to be dynamic
> and use 10%

I'm agree with the dynamic and use 10%.

>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Tested-by: Caesar Wang <wxt@...k-chips.com>

Tested for my rk3399 board. That's still happy work for my board.
..
[ 2891.541958] pwm_regulator_set_voltage: delay=38, min-v=800000, 
old-v=1024000
[ 2898.188785] pwm_regulator_set_voltage: delay=13, min-v=875000, 
old-v=800000
[ 2898.211873] pwm_regulator_set_voltage: delay=8, min-v=925000, 
old-v=877000
[ 2898.312026] pwm_regulator_set_voltage: delay=21, min-v=-800000, 
old-v=926000
..



> ---
> Note that this patch is atop Boris's recent PWM regulator fixes.  If
> desired it wouldn't be too hard to write it atop the old code, though
> quite honestly anyone using a PWM regulator should probably be using his
> new code.
>
>   drivers/regulator/pwm-regulator.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/regulator/pwm-regulator.c b/drivers/regulator/pwm-regulator.c
> index fa1c74c77bb0..de94d19f6e1f 100644
> --- a/drivers/regulator/pwm-regulator.c
> +++ b/drivers/regulator/pwm-regulator.c
> @@ -188,6 +188,7 @@ static int pwm_regulator_set_voltage(struct regulator_dev *rdev,
>   	struct pwm_state pstate;
>   	unsigned int diff_duty;
>   	unsigned int dutycycle;
> +	int old_uV = pwm_regulator_get_voltage(rdev);
>   	int ret;
>   
>   	pwm_init_state(drvdata->pwm, &pstate);
> @@ -219,8 +220,12 @@ static int pwm_regulator_set_voltage(struct regulator_dev *rdev,
>   		return ret;
>   	}
>   
> -	/* Delay required by PWM regulator to settle to the new voltage */
> -	usleep_range(ramp_delay, ramp_delay + 1000);
> +	if (ramp_delay == 0)
> +		return 0;
> +
> +	/* Ramp delay is in uV/uS. Adjust to uS and delay */
> +	ramp_delay = DIV_ROUND_UP(abs(req_min_uV - old_uV), ramp_delay);
> +	usleep_range(ramp_delay, ramp_delay + DIV_ROUND_UP(ramp_delay, 10));
>   
>   	return 0;
>   }