pwm: axi-pwmgen: Let .round_waveform_tohw() signal when request was rounded up
The .round_waveform_tohw() is supposed to return 1 if the requested
waveform cannot be implemented by rounding down all parameters. Also
adapt the corresponding comment to better describe why the implemented
procedure is right.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Tested-by: Trevor Gamblin <tgamblin@baylibre.com>
Link: https://lore.kernel.org/r/ba451573f0218d76645f068cec78bd97802cf010.1743844730.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
diff --git a/drivers/pwm/pwm-axi-pwmgen.c b/drivers/pwm/pwm-axi-pwmgen.c
index 4259a0db..4337c8f 100644
--- a/drivers/pwm/pwm-axi-pwmgen.c
+++ b/drivers/pwm/pwm-axi-pwmgen.c
@@ -75,6 +75,7 @@ static int axi_pwmgen_round_waveform_tohw(struct pwm_chip *chip,
{
struct axi_pwmgen_waveform *wfhw = _wfhw;
struct axi_pwmgen_ddata *ddata = axi_pwmgen_ddata_from_chip(chip);
+ int ret = 0;
if (wf->period_length_ns == 0) {
*wfhw = (struct axi_pwmgen_waveform){
@@ -91,12 +92,15 @@ static int axi_pwmgen_round_waveform_tohw(struct pwm_chip *chip,
if (wfhw->period_cnt == 0) {
/*
* The specified period is too short for the hardware.
- * Let's round .duty_cycle down to 0 to get a (somewhat)
- * valid result.
+ * So round up .period_cnt to 1 (i.e. the smallest
+ * possible period). With .duty_cycle and .duty_offset
+ * being less than or equal to .period, their rounded
+ * value must be 0.
*/
wfhw->period_cnt = 1;
wfhw->duty_cycle_cnt = 0;
wfhw->duty_offset_cnt = 0;
+ ret = 1;
} else {
wfhw->duty_cycle_cnt = min_t(u64,
mul_u64_u32_div(wf->duty_length_ns, ddata->clk_rate_hz, NSEC_PER_SEC),
@@ -111,7 +115,7 @@ static int axi_pwmgen_round_waveform_tohw(struct pwm_chip *chip,
pwm->hwpwm, wf->duty_length_ns, wf->period_length_ns, wf->duty_offset_ns,
ddata->clk_rate_hz, wfhw->period_cnt, wfhw->duty_cycle_cnt, wfhw->duty_offset_cnt);
- return 0;
+ return ret;
}
static int axi_pwmgen_round_waveform_fromhw(struct pwm_chip *chip, struct pwm_device *pwm,
