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>

diff --git a/drivers/media/rc/pwm-ir-tx.c b/drivers/media/rc/pwm-ir-tx.c
index cf51e27609759fa348dfdd05341ee27ae7d87365..fe368aebbc139a01d186cad4d25700a10f4c8215 100644 (file)
--- 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;