[v2] pwm:lpss: update pwm setting for Broxton

For Broxton PWM controller, base unit is defined as 8bit integer
and 14bit fraction, so need to update base unit setting to output
wave with right frequency.

Signed-off-by: Qipeng Zha <qipeng.zha@intel.com>
---
 drivers/pwm/pwm-lpss.c | 29 +++++++++++++++--------------
 drivers/pwm/pwm-lpss.h |  1 +
 2 files changed, 16 insertions(+), 14 deletions(-)

On Fri, Nov 13, 2015 at 06:34:10PM +0800, Qipeng Zha wrote:
> For Broxton PWM controller, base unit is defined as 8bit integer
> and 14bit fraction, so need to update base unit setting to output
> wave with right frequency.
> 
> Signed-off-by: Qipeng Zha <qipeng.zha@intel.com>

Looking good. Few minor comments, see below.

> ---
>  drivers/pwm/pwm-lpss.c | 29 +++++++++++++++--------------
>  drivers/pwm/pwm-lpss.h |  1 +
>  2 files changed, 16 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
> index 2504410..f4f8ee5 100644
> --- a/drivers/pwm/pwm-lpss.c
> +++ b/drivers/pwm/pwm-lpss.c
> @@ -14,6 +14,7 @@
>   */
>  
>  #include <linux/io.h>
> +#include <linux/time.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/pm_runtime.h>
> @@ -24,11 +25,8 @@
>  #define PWM_ENABLE			BIT(31)
>  #define PWM_SW_UPDATE			BIT(30)
>  #define PWM_BASE_UNIT_SHIFT		8
> -#define PWM_BASE_UNIT_MASK		0x00ffff00
>  #define PWM_ON_TIME_DIV_MASK		0x000000ff
>  #define PWM_DIVISION_CORRECTION		0x2
> -#define PWM_LIMIT			(0x8000 + PWM_DIVISION_CORRECTION)
> -#define NSECS_PER_SEC			1000000000UL
>  
>  /* Size of each PWM register space if multiple */
>  #define PWM_SIZE			0x400
> @@ -36,13 +34,14 @@
>  struct pwm_lpss_chip {
>  	struct pwm_chip chip;
>  	void __iomem *regs;
> -	unsigned long clk_rate;
> +	const struct pwm_lpss_boardinfo *info;
>  };
>  
>  /* BayTrail */
>  const struct pwm_lpss_boardinfo pwm_lpss_byt_info = {
>  	.clk_rate = 25000000,
>  	.npwm = 1,
> +	.base_unit_bits = 16,
>  };
>  EXPORT_SYMBOL_GPL(pwm_lpss_byt_info);
>  
> @@ -50,6 +49,7 @@ EXPORT_SYMBOL_GPL(pwm_lpss_byt_info);
>  const struct pwm_lpss_boardinfo pwm_lpss_bsw_info = {
>  	.clk_rate = 19200000,
>  	.npwm = 1,
> +	.base_unit_bits = 16,
>  };
>  EXPORT_SYMBOL_GPL(pwm_lpss_bsw_info);
>  
> @@ -57,6 +57,7 @@ EXPORT_SYMBOL_GPL(pwm_lpss_bsw_info);
>  const struct pwm_lpss_boardinfo pwm_lpss_bxt_info = {
>  	.clk_rate = 19200000,
>  	.npwm = 4,
> +	.base_unit_bits = 22,
>  };
>  EXPORT_SYMBOL_GPL(pwm_lpss_bxt_info);
>  
> @@ -84,23 +85,22 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  {
>  	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
>  	u8 on_time_div;
> -	unsigned long c;
> -	unsigned long long base_unit, freq = NSECS_PER_SEC;
> +	unsigned long c, base_unit_range;
> +	unsigned long long base_unit, freq = NSEC_PER_SEC;
>  	u32 ctrl;
>  
>  	do_div(freq, period_ns);
>  
> -	/* The equation is: base_unit = ((freq / c) * 65536) + correction */
> -	base_unit = freq * 65536;
> +	/* The equation is: base_unit = ((freq / c) * base_unit_range) + correction */
> +	base_unit_range = 1 << lpwm->info->base_unit_bits;

BIT()?

> +	base_unit = freq * base_unit_range;
>  
> -	c = lpwm->clk_rate;
> +	c = lpwm->info->clk_rate;
>  	if (!c)
>  		return -EINVAL;
>  
>  	do_div(base_unit, c);
>  	base_unit += PWM_DIVISION_CORRECTION;
> -	if (base_unit > PWM_LIMIT)
> -		return -EINVAL;
>  
>  	if (duty_ns <= 0)
>  		duty_ns = 1;
> @@ -109,8 +109,9 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  	pm_runtime_get_sync(chip->dev);
>  
>  	ctrl = pwm_lpss_read(pwm);
> -	ctrl &= ~(PWM_BASE_UNIT_MASK | PWM_ON_TIME_DIV_MASK);
> -	ctrl |= (u16) base_unit << PWM_BASE_UNIT_SHIFT;
> +	ctrl &= ~PWM_ON_TIME_DIV_MASK;
> +	ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT);
> +	ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;

I think you should first mask base_unit (with base_unit_range - 1) so that it
will not accidentally overwrite the upper bits.

>  	ctrl |= on_time_div;
>  	/* request PWM to update on next cycle */
>  	ctrl |= PWM_SW_UPDATE;
> @@ -156,7 +157,7 @@ struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
>  	if (IS_ERR(lpwm->regs))
>  		return ERR_CAST(lpwm->regs);
>  
> -	lpwm->clk_rate = info->clk_rate;
> +	lpwm->info = info;
>  	lpwm->chip.dev = dev;
>  	lpwm->chip.ops = &pwm_lpss_ops;
>  	lpwm->chip.base = -1;
> diff --git a/drivers/pwm/pwm-lpss.h b/drivers/pwm/pwm-lpss.h
> index e8cf337..04766e0 100644
> --- a/drivers/pwm/pwm-lpss.h
> +++ b/drivers/pwm/pwm-lpss.h
> @@ -21,6 +21,7 @@ struct pwm_lpss_chip;
>  struct pwm_lpss_boardinfo {
>  	unsigned long clk_rate;
>  	unsigned int npwm;
> +	unsigned long base_unit_bits;
>  };
>  
>  extern const struct pwm_lpss_boardinfo pwm_lpss_byt_info;
> -- 
> 1.8.3.2
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