> +static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
> + int duty_ns, int period_ns)
> +{
> + struct pwm_lpss_chip *lpwm = to_lpwm(chip);
> + u8 on_time_div;
> + unsigned long c = clk_get_rate(lpwm->clk);
> + unsigned long long base_unit, hz = 1000000000UL;
> + u32 ctrl;
> +
> + do_div(hz, period_ns);
> +
> + /* The equation is: base_unit = ((hz / c) * 65536) + correction */
> + base_unit = hz * 65536;
> + do_div(base_unit, c);
> + base_unit += PWM_DIVISION_CORRECTION;
> + if (base_unit > PWM_LIMIT)
> + return -EINVAL;
> +
> + if (duty_ns <= 0)
> + duty_ns = 1;
> + on_time_div = 255 - (255 * duty_ns / period_ns);
> +
> + ctrl = readl(lpwm->regs + PWM);
> + ctrl &= ~(PWM_BASE_UNIT_MASK | PWM_ON_TIME_DIV_MASK);
> + ctrl |= (u16) base_unit << PWM_BASE_UNIT_SHIFT;
> + ctrl |= on_time_div;
> + /* request PWM to update on next cycle */
> + ctrl |= PWM_SW_UPDATE;
> + writel(ctrl, lpwm->regs + PWM);
> +
Who handles the locking on all these functions. The pwm layer doesn't but
simnply exports stuff like pwm_config() directly to other bits of the
kernel so you are not guaranteed to be called via sysfs.
(This btw looks to be a problem with a pile of the other pwm drivers, and
with the pwm core code which doesn't properly lock its own handling of
pwm->duty_cycle and pwm->period in pwm_config(), nor pwm->polarity in
pwm_set_polarity).
I think the core config methods need some kind of locking ?
Alan
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