linux-kernel - Re: [PATCH 2/2] [RFC] cpufreq: omap: scale regulator from clk notifier

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Message-ID: <5004F638.6020301@nvidia.com>
Date:	Tue, 17 Jul 2012 10:50:56 +0530
From:	Prashant Gaikwad <pgaikwad@...dia.com>
To:	Mike Turquette <mturquette@...aro.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
	"rnayak@...com" <rnayak@...com>, "paul@...an.com" <paul@...an.com>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"ccross@...roid.com" <ccross@...roid.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/2] [RFC] cpufreq: omap: scale regulator from clk notifier

On Saturday 14 July 2012 05:46 AM, Mike Turquette wrote:
> This patch moves direct control of the MPU voltage regulator out of the
> cpufreq driver .target callback and instead puts that logic into a clock
> rate change notifier callback.
>
> The same frequency/voltage lookup via the OPP library is present, except
> that the calls to regulator_set_voltage are done from the clock
> framework instead of cpufreq.
>
> Ideally it would be nice to reduce the .target callback for OMAP's
> cpufreq driver to a simple call to clk_set_rate.  For now there is still
> some other stuff needed there (jiffies per loop, rounding the rate, etc
> etc).
>
> Not-signed-off-by: Mike Turquette<mturquette@...aro.org>
> ---
>   drivers/cpufreq/omap-cpufreq.c |  154 +++++++++++++++++++++++++---------------
>   1 file changed, 96 insertions(+), 58 deletions(-)
>

<snip>

>
> -static int __init omap_cpufreq_init(void)
> +static int mpu_clk_volt_scale_handler(struct notifier_block *nb,
> +	unsigned long flags, void *data)
>   {
> -	if (cpu_is_omap24xx())
> -		mpu_clk_name = "virt_prcm_set";
> -	else if (cpu_is_omap34xx())
> -		mpu_clk_name = "dpll1_ck";
> -	else if (cpu_is_omap44xx())
> -		mpu_clk_name = "dpll_mpu_ck";
> +	struct clk_notifier_data *cnd = data;
> +	unsigned long tol;
> +	int ret, volt_new, volt_old;
> +	struct opp *opp;
>
> -	if (!mpu_clk_name) {
> -		pr_err("%s: unsupported Silicon?\n", __func__);
> -		return -EINVAL;
> +	volt_old = regulator_get_voltage(mpu_reg);
> +	opp = opp_find_freq_exact(mpu_dev, cnd->new_rate, true);
> +	volt_new = opp_get_voltage(opp);
> +
> +	tol = volt_new * OPP_TOLERANCE / 100;
> +
> +	/* scaling up?  scale voltage before frequency */
> +	if (cnd->new_rate>  cnd->old_rate) {
> +		dev_dbg(mpu_dev, "cpufreq-omap: %d mV -->  %d mV\n",
> +				volt_old, volt_new);
> +
> +		ret = regulator_set_voltage(mpu_reg, volt_new - tol, volt_new + tol);
> +
> +		if (ret<  0) {
> +			dev_warn(mpu_dev, "%s: unable to scale voltage up.\n",
> +				 __func__);
> +			return NOTIFY_BAD;
> +		}
> +	}
> +
> +	/* scaling down?  scale voltage after frequency */
> +	if (cnd->new_rate<  cnd->old_rate) {
> +		dev_dbg(mpu_dev, "cpufreq-omap: %d mV -->  %d mV\n",
> +				volt_old, volt_new);
> +
> +		ret = regulator_set_voltage(mpu_reg, volt_new - tol, volt_new + tol);
> +
> +		if (ret<  0) {
> +			dev_warn(mpu_dev, "%s: unable to scale voltage down.\n",
> +				 __func__);
> +			return NOTIFY_BAD;
> +		}
>   	}

How are you checking pre and post rate change condition here? Need 
switch case for event?

>
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block mpu_clk_volt_scale_nb = {
> +	.notifier_call = mpu_clk_volt_scale_handler,
> +};
> +
> +

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