diff options
Diffstat (limited to 'drivers/pwm/pwm-img.c')
| -rw-r--r-- | drivers/pwm/pwm-img.c | 76 |
1 files changed, 64 insertions, 12 deletions
diff --git a/drivers/pwm/pwm-img.c b/drivers/pwm/pwm-img.c index 476171a768d6..8a029f9bc18c 100644 --- a/drivers/pwm/pwm-img.c +++ b/drivers/pwm/pwm-img.c @@ -16,6 +16,7 @@ #include <linux/mfd/syscon.h> #include <linux/module.h> #include <linux/of.h> +#include <linux/of_device.h> #include <linux/platform_device.h> #include <linux/pwm.h> #include <linux/regmap.h> @@ -38,7 +39,22 @@ #define PERIP_PWM_PDM_CONTROL_CH_MASK 0x1 #define PERIP_PWM_PDM_CONTROL_CH_SHIFT(ch) ((ch) * 4) -#define MAX_TMBASE_STEPS 65536 +/* + * PWM period is specified with a timebase register, + * in number of step periods. The PWM duty cycle is also + * specified in step periods, in the [0, $timebase] range. + * In other words, the timebase imposes the duty cycle + * resolution. Therefore, let's constraint the timebase to + * a minimum value to allow a sane range of duty cycle values. + * Imposing a minimum timebase, will impose a maximum PWM frequency. + * + * The value chosen is completely arbitrary. + */ +#define MIN_TMBASE_STEPS 16 + +struct img_pwm_soc_data { + u32 max_timebase; +}; struct img_pwm_chip { struct device *dev; @@ -47,6 +63,9 @@ struct img_pwm_chip { struct clk *sys_clk; void __iomem *base; struct regmap *periph_regs; + int max_period_ns; + int min_period_ns; + const struct img_pwm_soc_data *data; }; static inline struct img_pwm_chip *to_img_pwm_chip(struct pwm_chip *chip) @@ -72,24 +91,31 @@ static int img_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, u32 val, div, duty, timebase; unsigned long mul, output_clk_hz, input_clk_hz; struct img_pwm_chip *pwm_chip = to_img_pwm_chip(chip); + unsigned int max_timebase = pwm_chip->data->max_timebase; + + if (period_ns < pwm_chip->min_period_ns || + period_ns > pwm_chip->max_period_ns) { + dev_err(chip->dev, "configured period not in range\n"); + return -ERANGE; + } input_clk_hz = clk_get_rate(pwm_chip->pwm_clk); output_clk_hz = DIV_ROUND_UP(NSEC_PER_SEC, period_ns); mul = DIV_ROUND_UP(input_clk_hz, output_clk_hz); - if (mul <= MAX_TMBASE_STEPS) { + if (mul <= max_timebase) { div = PWM_CTRL_CFG_NO_SUB_DIV; timebase = DIV_ROUND_UP(mul, 1); - } else if (mul <= MAX_TMBASE_STEPS * 8) { + } else if (mul <= max_timebase * 8) { div = PWM_CTRL_CFG_SUB_DIV0; timebase = DIV_ROUND_UP(mul, 8); - } else if (mul <= MAX_TMBASE_STEPS * 64) { + } else if (mul <= max_timebase * 64) { div = PWM_CTRL_CFG_SUB_DIV1; timebase = DIV_ROUND_UP(mul, 64); - } else if (mul <= MAX_TMBASE_STEPS * 512) { + } else if (mul <= max_timebase * 512) { div = PWM_CTRL_CFG_SUB_DIV0_DIV1; timebase = DIV_ROUND_UP(mul, 512); - } else if (mul > MAX_TMBASE_STEPS * 512) { + } else if (mul > max_timebase * 512) { dev_err(chip->dev, "failed to configure timebase steps/divider value\n"); return -EINVAL; @@ -143,11 +169,27 @@ static const struct pwm_ops img_pwm_ops = { .owner = THIS_MODULE, }; +static const struct img_pwm_soc_data pistachio_pwm = { + .max_timebase = 255, +}; + +static const struct of_device_id img_pwm_of_match[] = { + { + .compatible = "img,pistachio-pwm", + .data = &pistachio_pwm, + }, + { } +}; +MODULE_DEVICE_TABLE(of, img_pwm_of_match); + static int img_pwm_probe(struct platform_device *pdev) { int ret; + u64 val; + unsigned long clk_rate; struct resource *res; struct img_pwm_chip *pwm; + const struct of_device_id *of_dev_id; pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL); if (!pwm) @@ -160,6 +202,11 @@ static int img_pwm_probe(struct platform_device *pdev) if (IS_ERR(pwm->base)) return PTR_ERR(pwm->base); + of_dev_id = of_match_device(img_pwm_of_match, &pdev->dev); + if (!of_dev_id) + return -ENODEV; + pwm->data = of_dev_id->data; + pwm->periph_regs = syscon_regmap_lookup_by_phandle(pdev->dev.of_node, "img,cr-periph"); if (IS_ERR(pwm->periph_regs)) @@ -189,6 +236,17 @@ static int img_pwm_probe(struct platform_device *pdev) goto disable_sysclk; } + clk_rate = clk_get_rate(pwm->pwm_clk); + + /* The maximum input clock divider is 512 */ + val = (u64)NSEC_PER_SEC * 512 * pwm->data->max_timebase; + do_div(val, clk_rate); + pwm->max_period_ns = val; + + val = (u64)NSEC_PER_SEC * MIN_TMBASE_STEPS; + do_div(val, clk_rate); + pwm->min_period_ns = val; + pwm->chip.dev = &pdev->dev; pwm->chip.ops = &img_pwm_ops; pwm->chip.base = -1; @@ -228,12 +286,6 @@ static int img_pwm_remove(struct platform_device *pdev) return pwmchip_remove(&pwm_chip->chip); } -static const struct of_device_id img_pwm_of_match[] = { - { .compatible = "img,pistachio-pwm", }, - { } -}; -MODULE_DEVICE_TABLE(of, img_pwm_of_match); - static struct platform_driver img_pwm_driver = { .driver = { .name = "img-pwm", |