Messages in this thread | | | Subject | Re: [PATCH 2/2] media: pwm-ir-tx: trigger edges from hrtimer interrupt context | From | Ivaylo Dimitrov <> | Date | Mon, 2 Oct 2023 08:49:47 +0300 |
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Hi,
On 1.10.23 г. 13:40 ч., Sean Young wrote: > The pwm-ir-tx driver has to turn the pwm signal on and off, and suffers > from delays as this is done in process context. Make this work in atomic > context. > > This makes the driver much more precise. > > Signed-off-by: Sean Young <sean@mess.org> > Cc: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com> > --- > drivers/media/rc/pwm-ir-tx.c | 79 ++++++++++++++++++++++++++++-------- > 1 file changed, 63 insertions(+), 16 deletions(-) > > diff --git a/drivers/media/rc/pwm-ir-tx.c b/drivers/media/rc/pwm-ir-tx.c > index c5f37c03af9c..557725a07a67 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 +19,13 @@ > > struct pwm_ir { > struct pwm_device *pwm; > - unsigned int carrier; > - unsigned int duty_cycle; > + struct hrtimer timer; > + struct completion completion; > + uint carrier; > + uint duty_cycle; > + uint *txbuf; > + uint txbuf_len; > + uint txbuf_index; > }; > > static const struct of_device_id pwm_ir_of_match[] = { > @@ -55,33 +62,65 @@ static int pwm_ir_tx(struct rc_dev *dev, unsigned int *txbuf, > struct pwm_ir *pwm_ir = dev->priv; > struct pwm_device *pwm = pwm_ir->pwm; > struct pwm_state state; > - int i; > - ktime_t edge; > - long delta; > + > + reinit_completion(&pwm_ir->completion);
You should not need that.
> > 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); > + state.enabled = false; > > - edge = ktime_get(); > + pwm_ir->txbuf = txbuf; > + pwm_ir->txbuf_len = count; > + pwm_ir->txbuf_index = 0; > > - for (i = 0; i < count; i++) { > - state.enabled = !(i % 2); > - pwm_apply_state(pwm, &state); > + pwm_apply_state(pwm, &state); >
ditto, first pwm control should be in the timer function
> - edge = ktime_add_us(edge, txbuf[i]); > - delta = ktime_us_delta(edge, ktime_get()); > - if (delta > 0) > - usleep_range(delta, delta + 10); > - } > + hrtimer_start(&pwm_ir->timer, 1000, HRTIMER_MODE_REL); >
why not just call it with 0 time?
> - state.enabled = false; > - pwm_apply_state(pwm, &state); > + wait_for_completion(&pwm_ir->completion); > > 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; > + > + if (pwm_ir->txbuf_index >= pwm_ir->txbuf_len) { > + /* Stop TX here */ > + pwm_disable(pwm_ir->pwm); > + > + complete(&pwm_ir->completion); > + > + return HRTIMER_NORESTART; > + } > + > + if (pwm_ir->txbuf_index % 2) > + pwm_disable(pwm_ir->pwm); > + else > + pwm_enable(pwm_ir->pwm); > +
pwm_ir->pwm->state.enabled = !(pwm_ir->txbuf_index % 2); pwm_apply_state(pwm_ir->pwm, pwm_ir->state);
> + 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; > @@ -96,8 +135,16 @@ static int pwm_ir_probe(struct platform_device *pdev) > if (IS_ERR(pwm_ir->pwm)) > return PTR_ERR(pwm_ir->pwm); > > + if (pwm_can_sleep(pwm_ir->pwm)) { > + dev_err(&pdev->dev, "unsupported pwm device: driver can sleep\n"); > + return -ENODEV; > + } > +
I think we shall not limit, but use high priority thread to support those drivers. I have that working on n900 with current (sleeping) pwm, see my reply on the other mail. Maybe we can combine both patches in a way to support both atomic and sleeping pwm drivers.
> pwm_ir->carrier = 38000; > pwm_ir->duty_cycle = 50; > + init_completion(&pwm_ir->completion); > + hrtimer_init(&pwm_ir->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); > + pwm_ir->timer.function = pwm_ir_timer; > > rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX); > if (!rcdev) >
Regards, Ivo
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