[v6,4/4] media: pwm-ir-tx: trigger edges from hrtimer interrupt context
Commit Message
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>
---
drivers/media/rc/pwm-ir-tx.c | 79 ++++++++++++++++++++++++++++++++++--
1 file changed, 76 insertions(+), 3 deletions(-)
Comments
On Wed, Nov 29, 2023 at 09:13:37AM +0000, Sean Young wrote:
> 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>
> ---
> drivers/media/rc/pwm-ir-tx.c | 79 ++++++++++++++++++++++++++++++++++--
> 1 file changed, 76 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/rc/pwm-ir-tx.c b/drivers/media/rc/pwm-ir-tx.c
> index cf51e2760975..8575c4596d7b 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;
> + uint *txbuf;
Maybe mark this as const to signal that it's not going to get modified?
> + uint txbuf_len;
> + uint txbuf_index;
uint is rather rare. Or so I thought. There seem to be quite a few
occurrences throughout the kernel. I'd still prefer unsigned int over
this abbreviated form, but ultimately up to you and Mauro to decide.
> };
>
> static const struct of_device_id pwm_ir_of_match[] = {
> @@ -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_is_atomic(pwm_ir->pwm)) {
> + 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;
> + } else {
> + dev_info(&pdev->dev, "tx will not be accurate as pwm device does not support atomic mode");
s/tx/TX and s/pwm/PWM/? Also, I'm a bit unhappy about "atomic mode" here
because the term is overloaded in PWM. If you call pwm_appy_*() then by
definition it's going to be "atomic" in the "atomic state" sense. So
maybe switch to something like:
"TX will not be accurate as PWM device might sleep"
?
Thierry
On Fri, Dec 08, 2023 at 05:29:55PM +0100, Thierry Reding wrote:
> On Wed, Nov 29, 2023 at 09:13:37AM +0000, Sean Young wrote:
> > 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>
> > ---
> > drivers/media/rc/pwm-ir-tx.c | 79 ++++++++++++++++++++++++++++++++++--
> > 1 file changed, 76 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/media/rc/pwm-ir-tx.c b/drivers/media/rc/pwm-ir-tx.c
> > index cf51e2760975..8575c4596d7b 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;
> > + uint *txbuf;
>
> Maybe mark this as const to signal that it's not going to get modified?
Ah nice, I usually forget const.
> > + uint txbuf_len;
> > + uint txbuf_index;
>
> uint is rather rare. Or so I thought. There seem to be quite a few
> occurrences throughout the kernel. I'd still prefer unsigned int over
> this abbreviated form, but ultimately up to you and Mauro to decide.
Yes, unsigned int is used a lot more. Changed.
> > 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_is_atomic(pwm_ir->pwm)) {
> > + 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;
> > + } else {
> > + dev_info(&pdev->dev, "tx will not be accurate as pwm device does not support atomic mode");
>
> s/tx/TX and s/pwm/PWM/? Also, I'm a bit unhappy about "atomic mode" here
> because the term is overloaded in PWM. If you call pwm_appy_*() then by
> definition it's going to be "atomic" in the "atomic state" sense. So
> maybe switch to something like:
>
> "TX will not be accurate as PWM device might sleep"
>
> ?
Very nice, changed.
Thanks
Sean
@@ -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;
+ uint *txbuf;
+ uint txbuf_len;
+ uint txbuf_index;
};
static const struct of_device_id pwm_ir_of_match[] = {
@@ -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_is_atomic(pwm_ir->pwm)) {
+ 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;
+ } else {
+ dev_info(&pdev->dev, "tx will not be accurate as pwm device does not support atomic mode");
+ rcdev->tx_ir = pwm_ir_tx;
+ }
+
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;