linux-kernel - Re: [PATCH 2/2] iio: trigger: stm32-timer: add power management support

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Date:   Sat, 7 Mar 2020 15:21:27 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Fabrice Gasnier <fabrice.gasnier@...com>
Cc:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <mcoquelin.stm32@...il.com>,
        <benjamin.gaignard@...com>, <alexandre.torgue@...com>,
        <olivier.moysan@...com>, <linux-iio@...r.kernel.org>,
        <lars@...afoo.de>, <knaack.h@....de>, <pmeerw@...erw.net>,
        <linux-stm32@...md-mailman.stormreply.com>
Subject: Re: [PATCH 2/2] iio: trigger: stm32-timer: add power management
 support

On Tue, 3 Mar 2020 15:59:45 +0100
Fabrice Gasnier <fabrice.gasnier@...com> wrote:

> Add suspend/resume PM sleep ops to stm32-timer-trigger driver.
> Register contents may be lost depending on low power modes.
> When going to low power, enforce the timer isn't active. Gracefully
> restore its state upon resume in case it's been left enabled prior to
> suspend.
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
Seems sensible. Applied,

Thanks,

Jonathan

> ---
>  drivers/iio/trigger/stm32-timer-trigger.c | 63 +++++++++++++++++++++++++++++++
>  1 file changed, 63 insertions(+)
> 
> diff --git a/drivers/iio/trigger/stm32-timer-trigger.c b/drivers/iio/trigger/stm32-timer-trigger.c
> index 32e1249..37545a8 100644
> --- a/drivers/iio/trigger/stm32-timer-trigger.c
> +++ b/drivers/iio/trigger/stm32-timer-trigger.c
> @@ -75,6 +75,15 @@ static const void *stm32h7_valids_table[][MAX_VALIDS] = {
>  	{ }, /* timer 17 */
>  };
>  
> +struct stm32_timer_trigger_regs {
> +	u32 cr1;
> +	u32 cr2;
> +	u32 psc;
> +	u32 arr;
> +	u32 cnt;
> +	u32 smcr;
> +};
> +
>  struct stm32_timer_trigger {
>  	struct device *dev;
>  	struct regmap *regmap;
> @@ -86,6 +95,7 @@ struct stm32_timer_trigger {
>  	bool has_trgo2;
>  	struct mutex lock; /* concurrent sysfs configuration */
>  	struct list_head tr_list;
> +	struct stm32_timer_trigger_regs bak;
>  };
>  
>  struct stm32_timer_trigger_cfg {
> @@ -812,6 +822,58 @@ static int stm32_timer_trigger_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> +static int __maybe_unused stm32_timer_trigger_suspend(struct device *dev)
> +{
> +	struct stm32_timer_trigger *priv = dev_get_drvdata(dev);
> +
> +	/* Only take care of enabled timer: don't disturb other MFD child */
> +	if (priv->enabled) {
> +		/* Backup registers that may get lost in low power mode */
> +		regmap_read(priv->regmap, TIM_CR1, &priv->bak.cr1);
> +		regmap_read(priv->regmap, TIM_CR2, &priv->bak.cr2);
> +		regmap_read(priv->regmap, TIM_PSC, &priv->bak.psc);
> +		regmap_read(priv->regmap, TIM_ARR, &priv->bak.arr);
> +		regmap_read(priv->regmap, TIM_CNT, &priv->bak.cnt);
> +		regmap_read(priv->regmap, TIM_SMCR, &priv->bak.smcr);
> +
> +		/* Disable the timer */
> +		regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0);
> +		clk_disable(priv->clk);
> +	}
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused stm32_timer_trigger_resume(struct device *dev)
> +{
> +	struct stm32_timer_trigger *priv = dev_get_drvdata(dev);
> +	int ret;
> +
> +	if (priv->enabled) {
> +		ret = clk_enable(priv->clk);
> +		if (ret)
> +			return ret;
> +
> +		/* restore master/slave modes */
> +		regmap_write(priv->regmap, TIM_SMCR, priv->bak.smcr);
> +		regmap_write(priv->regmap, TIM_CR2, priv->bak.cr2);
> +
> +		/* restore sampling_frequency (trgo / trgo2 triggers) */
> +		regmap_write(priv->regmap, TIM_PSC, priv->bak.psc);
> +		regmap_write(priv->regmap, TIM_ARR, priv->bak.arr);
> +		regmap_write(priv->regmap, TIM_CNT, priv->bak.cnt);
> +
> +		/* Also re-enables the timer */
> +		regmap_write(priv->regmap, TIM_CR1, priv->bak.cr1);
> +	}
> +
> +	return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(stm32_timer_trigger_pm_ops,
> +			 stm32_timer_trigger_suspend,
> +			 stm32_timer_trigger_resume);
> +
>  static const struct stm32_timer_trigger_cfg stm32_timer_trg_cfg = {
>  	.valids_table = valids_table,
>  	.num_valids_table = ARRAY_SIZE(valids_table),
> @@ -840,6 +902,7 @@ static struct platform_driver stm32_timer_trigger_driver = {
>  	.driver = {
>  		.name = "stm32-timer-trigger",
>  		.of_match_table = stm32_trig_of_match,
> +		.pm = &stm32_timer_trigger_pm_ops,
>  	},
>  };
>  module_platform_driver(stm32_timer_trigger_driver);