Re: [PATCH v3 1/2] drivers: pwm: pwm-atmel: switch to atomic PWM

[Boris Brezillon]

On Wed, 22 Mar 2017 15:29:34 +0200
Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx> wrote:

> The currently Atmel PWM controllers supported by this driver
> could change period or duty factor without channel disable,
> for regular channels (sama5d3 support this by using period
> or duty factor update registers, sam9rl support this by
> writing channel update register and select the corresponding
> update: period or duty factor). The chip doesn't support run
> time changings of signal polarity. To take advantage of
> atomic PWM framework and let controller works without glitches,
> in this patch only the duty factor could be changed without
> disabling PWM channel. For period and signal polarity the
> atomic PWM is simulated by disabling + enabling the right PWM channel.
> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>

Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>

> 
> ---
>  drivers/pwm/pwm-atmel.c | 273 +++++++++++++++++++++++-------------------------
>  1 file changed, 129 insertions(+), 144 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
> index 67a7023..f147154 100644
> --- a/drivers/pwm/pwm-atmel.c
> +++ b/drivers/pwm/pwm-atmel.c
> @@ -58,17 +58,22 @@
>  #define PWM_MAX_PRD		0xFFFF
>  #define PRD_MAX_PRES		10
>  
> +struct atmel_pwm_registers {
> +	u8 period;
> +	u8 period_upd;
> +	u8 duty;
> +	u8 duty_upd;
> +};
> +
>  struct atmel_pwm_chip {
>  	struct pwm_chip chip;
>  	struct clk *clk;
>  	void __iomem *base;
> +	const struct atmel_pwm_registers *regs;
>  
>  	unsigned int updated_pwms;
>  	/* ISR is cleared when read, ensure only one thread does that */
>  	struct mutex isr_lock;
> -
> -	void (*config)(struct pwm_chip *chip, struct pwm_device *pwm,
> -		       unsigned long dty, unsigned long prd);
>  };
>  
>  static inline struct atmel_pwm_chip *to_atmel_pwm_chip(struct pwm_chip *chip)
> @@ -105,153 +110,71 @@ static inline void atmel_pwm_ch_writel(struct atmel_pwm_chip *chip,
>  	writel_relaxed(val, chip->base + base + offset);
>  }
>  
> -static int atmel_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> -			    int duty_ns, int period_ns)
> +static int atmel_pwm_calculate_cprd_and_pres(struct pwm_chip *chip,
> +					     const struct pwm_state *state,
> +					     unsigned long *cprd, u32 *pres)
>  {
>  	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
> -	unsigned long prd, dty;
> -	unsigned long long div;
> -	unsigned int pres = 0;
> -	u32 val;
> -	int ret;
> -
> -	if (pwm_is_enabled(pwm) && (period_ns != pwm_get_period(pwm))) {
> -		dev_err(chip->dev, "cannot change PWM period while enabled\n");
> -		return -EBUSY;
> -	}
> +	unsigned long long cycles = state->period;
>  
>  	/* Calculate the period cycles and prescale value */
> -	div = (unsigned long long)clk_get_rate(atmel_pwm->clk) * period_ns;
> -	do_div(div, NSEC_PER_SEC);
> +	cycles *= clk_get_rate(atmel_pwm->clk);
> +	do_div(cycles, NSEC_PER_SEC);
>  
> -	while (div > PWM_MAX_PRD) {
> -		div >>= 1;
> -		pres++;
> -	}
> +	for (*pres = 0; cycles > PWM_MAX_PRD; cycles >>= 1)
> +		(*pres)++;
>  
> -	if (pres > PRD_MAX_PRES) {
> +	if (*pres > PRD_MAX_PRES) {
>  		dev_err(chip->dev, "pres exceeds the maximum value\n");
>  		return -EINVAL;
>  	}
>  
> -	/* Calculate the duty cycles */
> -	prd = div;
> -	div *= duty_ns;
> -	do_div(div, period_ns);
> -	dty = prd - div;
> -
> -	ret = clk_enable(atmel_pwm->clk);
> -	if (ret) {
> -		dev_err(chip->dev, "failed to enable PWM clock\n");
> -		return ret;
> -	}
> -
> -	/* It is necessary to preserve CPOL, inside CMR */
> -	val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
> -	val = (val & ~PWM_CMR_CPRE_MSK) | (pres & PWM_CMR_CPRE_MSK);
> -	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
> -	atmel_pwm->config(chip, pwm, dty, prd);
> -	mutex_lock(&atmel_pwm->isr_lock);
> -	atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR);
> -	atmel_pwm->updated_pwms &= ~(1 << pwm->hwpwm);
> -	mutex_unlock(&atmel_pwm->isr_lock);
> +	*cprd = cycles;
>  
> -	clk_disable(atmel_pwm->clk);
> -	return ret;
> +	return 0;
>  }
>  
> -static void atmel_pwm_config_v1(struct pwm_chip *chip, struct pwm_device *pwm,
> -				unsigned long dty, unsigned long prd)
> +static void atmel_pwm_calculate_cdty(const struct pwm_state *state,
> +				     unsigned long cprd, unsigned long *cdty)
>  {
> -	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
> -	unsigned int val;
> +	unsigned long long cycles = state->duty_cycle;
>  
> -
> -	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CUPD, dty);
> -
> -	val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
> -	val &= ~PWM_CMR_UPD_CDTY;
> -	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
> -
> -	/*
> -	 * If the PWM channel is enabled, only update CDTY by using the update
> -	 * register, it needs to set bit 10 of CMR to 0
> -	 */
> -	if (pwm_is_enabled(pwm))
> -		return;
> -	/*
> -	 * If the PWM channel is disabled, write value to duty and period
> -	 * registers directly.
> -	 */
> -	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CDTY, dty);
> -	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CPRD, prd);
> +	cycles *= cprd;
> +	do_div(cycles, state->period);
> +	*cdty = cprd - cycles;
>  }
>  
> -static void atmel_pwm_config_v2(struct pwm_chip *chip, struct pwm_device *pwm,
> -				unsigned long dty, unsigned long prd)
> -{
> -	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
> -
> -	if (pwm_is_enabled(pwm)) {
> -		/*
> -		 * If the PWM channel is enabled, using the duty update register
> -		 * to update the value.
> -		 */
> -		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV2_CDTYUPD, dty);
> -	} else {
> -		/*
> -		 * If the PWM channel is disabled, write value to duty and
> -		 * period registers directly.
> -		 */
> -		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV2_CDTY, dty);
> -		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV2_CPRD, prd);
> -	}
> -}
> -
> -static int atmel_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
> -				  enum pwm_polarity polarity)
> +static void atmel_pwm_update_cdty(struct pwm_chip *chip, struct pwm_device *pwm,
> +				  unsigned long cdty)
>  {
>  	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
>  	u32 val;
> -	int ret;
> -
> -	val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
>  
> -	if (polarity == PWM_POLARITY_NORMAL)
> -		val &= ~PWM_CMR_CPOL;
> -	else
> -		val |= PWM_CMR_CPOL;
> -
> -	ret = clk_enable(atmel_pwm->clk);
> -	if (ret) {
> -		dev_err(chip->dev, "failed to enable PWM clock\n");
> -		return ret;
> +	if (atmel_pwm->regs->duty_upd ==
> +	    atmel_pwm->regs->period_upd) {
> +		val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
> +		val &= ~PWM_CMR_UPD_CDTY;
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
>  	}
>  
> -	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
> -
> -	clk_disable(atmel_pwm->clk);
> -
> -	return 0;
> +	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
> +			    atmel_pwm->regs->duty_upd, cdty);
>  }
>  
> -static int atmel_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> +static void atmel_pwm_set_cprd_cdty(struct pwm_chip *chip,
> +				    struct pwm_device *pwm,
> +				    unsigned long cprd, unsigned long cdty)
>  {
>  	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
> -	int ret;
> -
> -	ret = clk_enable(atmel_pwm->clk);
> -	if (ret) {
> -		dev_err(chip->dev, "failed to enable PWM clock\n");
> -		return ret;
> -	}
>  
> -	atmel_pwm_writel(atmel_pwm, PWM_ENA, 1 << pwm->hwpwm);
> -
> -	return 0;
> +	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
> +			    atmel_pwm->regs->duty, cdty);
> +	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
> +			    atmel_pwm->regs->period, cprd);
>  }
>  
> -static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> +static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm,
> +			      bool disable_clk)
>  {
>  	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
>  	unsigned long timeout = jiffies + 2 * HZ;
> @@ -282,37 +205,99 @@ static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
>  	       time_before(jiffies, timeout))
>  		usleep_range(10, 100);
>  
> -	clk_disable(atmel_pwm->clk);
> +	if (disable_clk)
> +		clk_disable(atmel_pwm->clk);
> +}
> +
> +static int atmel_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +			   struct pwm_state *state)
> +{
> +	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
> +	struct pwm_state cstate;
> +	unsigned long cprd, cdty;
> +	u32 pres, val;
> +	int ret;
> +
> +	pwm_get_state(pwm, &cstate);
> +
> +	if (state->enabled) {
> +		if (cstate.enabled &&
> +		    cstate.polarity == state->polarity &&
> +		    cstate.period == state->period) {
> +			cprd = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
> +						  atmel_pwm->regs->period);
> +			atmel_pwm_calculate_cdty(state, cprd, &cdty);
> +			atmel_pwm_update_cdty(chip, pwm, cdty);
> +			return 0;
> +		}
> +
> +		ret = atmel_pwm_calculate_cprd_and_pres(chip, state, &cprd,
> +							&pres);
> +		if (ret) {
> +			dev_err(chip->dev,
> +				"failed to calculate cprd and prescaler\n");
> +			return ret;
> +		}
> +
> +		atmel_pwm_calculate_cdty(state, cprd, &cdty);
> +
> +		if (cstate.enabled) {
> +			atmel_pwm_disable(chip, pwm, false);
> +		} else {
> +			ret = clk_enable(atmel_pwm->clk);
> +			if (ret) {
> +				dev_err(chip->dev, "failed to enable clock\n");
> +				return ret;
> +			}
> +		}
> +
> +		/* It is necessary to preserve CPOL, inside CMR */
> +		val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
> +		val = (val & ~PWM_CMR_CPRE_MSK) | (pres & PWM_CMR_CPRE_MSK);
> +		if (state->polarity == PWM_POLARITY_NORMAL)
> +			val &= ~PWM_CMR_CPOL;
> +		else
> +			val |= PWM_CMR_CPOL;
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
> +		atmel_pwm_set_cprd_cdty(chip, pwm, cprd, cdty);
> +		mutex_lock(&atmel_pwm->isr_lock);
> +		atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR);
> +		atmel_pwm->updated_pwms &= ~(1 << pwm->hwpwm);
> +		mutex_unlock(&atmel_pwm->isr_lock);
> +		atmel_pwm_writel(atmel_pwm, PWM_ENA, 1 << pwm->hwpwm);
> +	} else if (cstate.enabled) {
> +		atmel_pwm_disable(chip, pwm, true);
> +	}
> +
> +	return 0;
>  }
>  
>  static const struct pwm_ops atmel_pwm_ops = {
> -	.config = atmel_pwm_config,
> -	.set_polarity = atmel_pwm_set_polarity,
> -	.enable = atmel_pwm_enable,
> -	.disable = atmel_pwm_disable,
> +	.apply = atmel_pwm_apply,
>  	.owner = THIS_MODULE,
>  };
>  
> -struct atmel_pwm_data {
> -	void (*config)(struct pwm_chip *chip, struct pwm_device *pwm,
> -		       unsigned long dty, unsigned long prd);
> -};
> -
> -static const struct atmel_pwm_data atmel_pwm_data_v1 = {
> -	.config = atmel_pwm_config_v1,
> +static const struct atmel_pwm_registers atmel_pwm_regs_v1 = {
> +	.period		= PWMV1_CPRD,
> +	.period_upd	= PWMV1_CUPD,
> +	.duty		= PWMV1_CDTY,
> +	.duty_upd	= PWMV1_CUPD,
>  };
>  
> -static const struct atmel_pwm_data atmel_pwm_data_v2 = {
> -	.config = atmel_pwm_config_v2,
> +static const struct atmel_pwm_registers atmel_pwm_regs_v2 = {
> +	.period		= PWMV2_CPRD,
> +	.period_upd	= PWMV2_CPRDUPD,
> +	.duty		= PWMV2_CDTY,
> +	.duty_upd	= PWMV2_CDTYUPD,
>  };
>  
>  static const struct platform_device_id atmel_pwm_devtypes[] = {
>  	{
>  		.name = "at91sam9rl-pwm",
> -		.driver_data = (kernel_ulong_t)&atmel_pwm_data_v1,
> +		.driver_data = (kernel_ulong_t)&atmel_pwm_regs_v1,
>  	}, {
>  		.name = "sama5d3-pwm",
> -		.driver_data = (kernel_ulong_t)&atmel_pwm_data_v2,
> +		.driver_data = (kernel_ulong_t)&atmel_pwm_regs_v2,
>  	}, {
>  		/* sentinel */
>  	},
> @@ -322,17 +307,17 @@ MODULE_DEVICE_TABLE(platform, atmel_pwm_devtypes);
>  static const struct of_device_id atmel_pwm_dt_ids[] = {
>  	{
>  		.compatible = "atmel,at91sam9rl-pwm",
> -		.data = &atmel_pwm_data_v1,
> +		.data = &atmel_pwm_regs_v1,
>  	}, {
>  		.compatible = "atmel,sama5d3-pwm",
> -		.data = &atmel_pwm_data_v2,
> +		.data = &atmel_pwm_regs_v2,
>  	}, {
>  		/* sentinel */
>  	},
>  };
>  MODULE_DEVICE_TABLE(of, atmel_pwm_dt_ids);
>  
> -static inline const struct atmel_pwm_data *
> +static inline const struct atmel_pwm_registers *
>  atmel_pwm_get_driver_data(struct platform_device *pdev)
>  {
>  	const struct platform_device_id *id;
> @@ -342,18 +327,18 @@ atmel_pwm_get_driver_data(struct platform_device *pdev)
>  
>  	id = platform_get_device_id(pdev);
>  
> -	return (struct atmel_pwm_data *)id->driver_data;
> +	return (struct atmel_pwm_registers *)id->driver_data;
>  }
>  
>  static int atmel_pwm_probe(struct platform_device *pdev)
>  {
> -	const struct atmel_pwm_data *data;
> +	const struct atmel_pwm_registers *regs;
>  	struct atmel_pwm_chip *atmel_pwm;
>  	struct resource *res;
>  	int ret;
>  
> -	data = atmel_pwm_get_driver_data(pdev);
> -	if (!data)
> +	regs = atmel_pwm_get_driver_data(pdev);
> +	if (!regs)
>  		return -ENODEV;
>  
>  	atmel_pwm = devm_kzalloc(&pdev->dev, sizeof(*atmel_pwm), GFP_KERNEL);
> @@ -385,7 +370,7 @@ static int atmel_pwm_probe(struct platform_device *pdev)
>  
>  	atmel_pwm->chip.base = -1;
>  	atmel_pwm->chip.npwm = 4;
> -	atmel_pwm->config = data->config;
> +	atmel_pwm->regs = regs;
>  	atmel_pwm->updated_pwms = 0;
>  	mutex_init(&atmel_pwm->isr_lock);
>