diff options
author | Sean Young <sean@mess.org> | 2023-12-19 16:30:29 +0000 |
---|---|---|
committer | Thierry Reding <thierry.reding@gmail.com> | 2023-12-20 16:12:49 +0100 |
commit | 363d0e56285e80cda997d41d94c22313b673557d (patch) | |
tree | 70919832f006a4b32c710ff46360726529961d27 /drivers/media | |
parent | fcc76072935935082efa127b97c7ddd880d2d793 (diff) | |
download | lwn-363d0e56285e80cda997d41d94c22313b673557d.tar.gz lwn-363d0e56285e80cda997d41d94c22313b673557d.zip |
media: pwm-ir-tx: Trigger edges from hrtimer interrupt context
This makes the generated IR much more precise. Before this change, the
driver is unreliable and many users opted to use gpio-ir-tx instead.
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'drivers/media')
-rw-r--r-- | drivers/media/rc/pwm-ir-tx.c | 83 |
1 files changed, 78 insertions, 5 deletions
diff --git a/drivers/media/rc/pwm-ir-tx.c b/drivers/media/rc/pwm-ir-tx.c index cf51e2760975..fe368aebbc13 100644 --- a/drivers/media/rc/pwm-ir-tx.c +++ b/drivers/media/rc/pwm-ir-tx.c @@ -10,6 +10,8 @@ #include <linux/slab.h> #include <linux/of.h> #include <linux/platform_device.h> +#include <linux/hrtimer.h> +#include <linux/completion.h> #include <media/rc-core.h> #define DRIVER_NAME "pwm-ir-tx" @@ -17,8 +19,14 @@ struct pwm_ir { struct pwm_device *pwm; - unsigned int carrier; - unsigned int duty_cycle; + struct hrtimer timer; + struct completion tx_done; + struct pwm_state *state; + u32 carrier; + u32 duty_cycle; + const unsigned int *txbuf; + unsigned int txbuf_len; + unsigned int txbuf_index; }; static const struct of_device_id pwm_ir_of_match[] = { @@ -49,8 +57,8 @@ static int pwm_ir_set_carrier(struct rc_dev *dev, u32 carrier) return 0; } -static int pwm_ir_tx(struct rc_dev *dev, unsigned int *txbuf, - unsigned int count) +static int pwm_ir_tx_sleep(struct rc_dev *dev, unsigned int *txbuf, + unsigned int count) { struct pwm_ir *pwm_ir = dev->priv; struct pwm_device *pwm = pwm_ir->pwm; @@ -82,6 +90,62 @@ static int pwm_ir_tx(struct rc_dev *dev, unsigned int *txbuf, return count; } +static int pwm_ir_tx_atomic(struct rc_dev *dev, unsigned int *txbuf, + unsigned int count) +{ + struct pwm_ir *pwm_ir = dev->priv; + struct pwm_device *pwm = pwm_ir->pwm; + struct pwm_state state; + + pwm_init_state(pwm, &state); + + state.period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, pwm_ir->carrier); + pwm_set_relative_duty_cycle(&state, pwm_ir->duty_cycle, 100); + + pwm_ir->txbuf = txbuf; + pwm_ir->txbuf_len = count; + pwm_ir->txbuf_index = 0; + pwm_ir->state = &state; + + hrtimer_start(&pwm_ir->timer, 0, HRTIMER_MODE_REL); + + wait_for_completion(&pwm_ir->tx_done); + + return count; +} + +static enum hrtimer_restart pwm_ir_timer(struct hrtimer *timer) +{ + struct pwm_ir *pwm_ir = container_of(timer, struct pwm_ir, timer); + ktime_t now; + + /* + * If we happen to hit an odd latency spike, loop through the + * pulses until we catch up. + */ + do { + u64 ns; + + pwm_ir->state->enabled = !(pwm_ir->txbuf_index % 2); + pwm_apply_atomic(pwm_ir->pwm, pwm_ir->state); + + if (pwm_ir->txbuf_index >= pwm_ir->txbuf_len) { + complete(&pwm_ir->tx_done); + + return HRTIMER_NORESTART; + } + + ns = US_TO_NS(pwm_ir->txbuf[pwm_ir->txbuf_index]); + hrtimer_add_expires_ns(timer, ns); + + pwm_ir->txbuf_index++; + + now = timer->base->get_time(); + } while (hrtimer_get_expires_tv64(timer) < now); + + return HRTIMER_RESTART; +} + static int pwm_ir_probe(struct platform_device *pdev) { struct pwm_ir *pwm_ir; @@ -103,10 +167,19 @@ static int pwm_ir_probe(struct platform_device *pdev) if (!rcdev) return -ENOMEM; + if (pwm_might_sleep(pwm_ir->pwm)) { + dev_info(&pdev->dev, "TX will not be accurate as PWM device might sleep\n"); + rcdev->tx_ir = pwm_ir_tx_sleep; + } else { + init_completion(&pwm_ir->tx_done); + hrtimer_init(&pwm_ir->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + pwm_ir->timer.function = pwm_ir_timer; + rcdev->tx_ir = pwm_ir_tx_atomic; + } + rcdev->priv = pwm_ir; rcdev->driver_name = DRIVER_NAME; rcdev->device_name = DEVICE_NAME; - rcdev->tx_ir = pwm_ir_tx; rcdev->s_tx_duty_cycle = pwm_ir_set_duty_cycle; rcdev->s_tx_carrier = pwm_ir_set_carrier; |