diff options
Diffstat (limited to 'drivers/pwm')
| -rw-r--r-- | drivers/pwm/pwm-lpss.c | 52 |
1 files changed, 43 insertions, 9 deletions
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index 09869f91d2d0..46670276690d 100644 --- a/drivers/pwm/pwm-lpss.c +++ b/drivers/pwm/pwm-lpss.c @@ -15,6 +15,7 @@ #include <linux/delay.h> #include <linux/io.h> +#include <linux/iopoll.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/pm_runtime.h> @@ -80,17 +81,37 @@ static inline void pwm_lpss_write(const struct pwm_device *pwm, u32 value) writel(value, lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM); } -static void pwm_lpss_update(struct pwm_device *pwm) +static int pwm_lpss_update(struct pwm_device *pwm) { + struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip); + const void __iomem *addr = lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM; + const unsigned int ms = 500 * USEC_PER_MSEC; + u32 val; + int err; + + pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_SW_UPDATE); + /* - * Set a limit for busyloop since not all implementations correctly - * clear PWM_SW_UPDATE bit (at least it's not visible on OS side). + * PWM Configuration register has SW_UPDATE bit that is set when a new + * configuration is written to the register. The bit is automatically + * cleared at the start of the next output cycle by the IP block. + * + * If one writes a new configuration to the register while it still has + * the bit enabled, PWM may freeze. That is, while one can still write + * to the register, it won't have an effect. Thus, we try to sleep long + * enough that the bit gets cleared and make sure the bit is not + * enabled while we update the configuration. */ - unsigned int count = 10; + err = readl_poll_timeout(addr, val, !(val & PWM_SW_UPDATE), 40, ms); + if (err) + dev_err(pwm->chip->dev, "PWM_SW_UPDATE was not cleared\n"); - pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_SW_UPDATE); - while (pwm_lpss_read(pwm) & PWM_SW_UPDATE && --count) - usleep_range(10, 20); + return err; +} + +static inline int pwm_lpss_is_updating(struct pwm_device *pwm) +{ + return (pwm_lpss_read(pwm) & PWM_SW_UPDATE) ? -EBUSY : 0; } static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, @@ -129,16 +150,29 @@ static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm, struct pwm_state *state) { struct pwm_lpss_chip *lpwm = to_lpwm(chip); + int ret; if (state->enabled) { if (!pwm_is_enabled(pwm)) { pm_runtime_get_sync(chip->dev); + ret = pwm_lpss_is_updating(pwm); + if (ret) { + pm_runtime_put(chip->dev); + return ret; + } pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period); - pwm_lpss_update(pwm); + ret = pwm_lpss_update(pwm); + if (ret) { + pm_runtime_put(chip->dev); + return ret; + } pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_ENABLE); } else { + ret = pwm_lpss_is_updating(pwm); + if (ret) + return ret; pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period); - pwm_lpss_update(pwm); + return pwm_lpss_update(pwm); } } else if (pwm_is_enabled(pwm)) { pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE); |