Hello Sean, On Thu, Oct 28, 2021 at 10:14:42AM +0100, Sean Young wrote: > On Thu, Oct 28, 2021 at 08:45:13AM +0200, Uwe Kleine-König wrote: > > The conversion is right (I think), > > We still have the problem that the pwm drivers calculate the period > incorrectly by rounding down (except pwm-bcm2835). So the period is not > as good as it could be in most cases, but this driver can't do anything > about that. Yeah, some time ago I started coding a round_state function (wip at https://git.pengutronix.de/cgit/ukl/linux/commit/?h=pwm-wip&id=ae348eb6a55d6526f30ef4a49819197d9616391e) but this was pushed down on my todo-list by more important stuff. If you want to experiment with that ... > > note this could be optimized a bit > > further: state.period only depends on carrier which rarely changes, so > > the calculation could be done in pwm_ir_set_carrier(). Ditto for duty > > which only depends on state.period and pwm_ir->duty_cycle. (This is for > > a separate commit though.) > > I'm not sure what caching this is much of a win. The calculation is a few > instructions, so you're not winning in the way of speed. On the flip side > you use more memory since pwm_state has to be kmalloc() rather than existing I tested a bit with this patch on top of Maíra's: diff --git a/drivers/media/rc/pwm-ir-tx.c b/drivers/media/rc/pwm-ir-tx.c index 105a9c24f1e3..7585c21775bc 100644 --- a/drivers/media/rc/pwm-ir-tx.c +++ b/drivers/media/rc/pwm-ir-tx.c @@ -17,7 +17,7 @@ struct pwm_ir { struct pwm_device *pwm; - unsigned int carrier; + struct pwm_state state; unsigned int duty_cycle; }; @@ -32,6 +32,7 @@ static int pwm_ir_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle) struct pwm_ir *pwm_ir = dev->priv; pwm_ir->duty_cycle = duty_cycle; + pwm_set_relative_duty_cycle(&pwm_ir->state, pwm_ir->duty_cycle, 100); return 0; } @@ -43,7 +44,8 @@ static int pwm_ir_set_carrier(struct rc_dev *dev, u32 carrier) if (!carrier) return -EINVAL; - pwm_ir->carrier = carrier; + pwm_ir->state.period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, carrier); + pwm_set_relative_duty_cycle(&pwm_ir->state, pwm_ir->duty_cycle, 100); return 0; } @@ -53,21 +55,15 @@ 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; - 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); - edge = ktime_get(); for (i = 0; i < count; i++) { - state.enabled = !(i % 2); - pwm_apply_state(pwm, &state); + pwm_ir->state.enabled = !(i % 2); + pwm_apply_state(pwm, &pwm_ir->state); edge = ktime_add_us(edge, txbuf[i]); delta = ktime_us_delta(edge, ktime_get()); @@ -75,8 +71,8 @@ static int pwm_ir_tx(struct rc_dev *dev, unsigned int *txbuf, usleep_range(delta, delta + 10); } - state.enabled = false; - pwm_apply_state(pwm, &state); + pwm_ir->state.enabled = false; + pwm_apply_state(pwm, &pwm_ir->state); return count; } @@ -95,8 +91,9 @@ static int pwm_ir_probe(struct platform_device *pdev) if (IS_ERR(pwm_ir->pwm)) return PTR_ERR(pwm_ir->pwm); - pwm_ir->carrier = 38000; - pwm_ir->duty_cycle = 50; + pwm_ir->state.duty_cycle = 50; + pwm_init_state(pwm_ir->pwm, &pwm_ir->state); + pwm_ir_set_carrier(rcdev, 38000); rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX); if (!rcdev) bloat-o-meter reports (for an arm allmodconfig build) add/remove: 0/0 grow/shrink: 3/1 up/down: 644/-396 (248) Function old new delta pwm_ir_probe 372 676 +304 pwm_ir_set_carrier 108 292 +184 pwm_ir_set_duty_cycle 68 224 +156 pwm_ir_tx 908 512 -396 Total: Before=2302, After=2550, chg +10.77% struct pwm_ir increases from 12 bytes to 40 bytes. The stack space required by pwm_ir_tx decreases from 60 to 36 I don't know exactly how kmalloc works internally. Maybe allocating a structure of size 40 bytes doesn't need more memory than a structure of size 12? I didn't check how runtimes change, but the size decrease of pwm_ir_tx() is nice and might save a bit of runtime. Probably it depends on your focus if this change is good for you or not. > just on the stack, and both ioctl handlers and the probe function need to > recalculate the period/duty cycle, so there is a slight increase in code size. > > This change does not improve anything measurably and only increases code > complexity. You did measure? Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |
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