[PATCH v3 2/3] leds: rgb: leds-qcom-lpg: Fix pwm resolution max for Hi-Res PWMs

Abel Vesa
2025-03-03T11:53:13Z

Ideally, the requested duty cycle should never translate to a PWM
value higher than the selected resolution (PWM size), but currently the
best matched period is never reported back to the PWM consumer, so the
consumer will still be using the requested period which is higher than
the best matched one. This will result in PWM consumer requesting
duty cycle values higher than the allowed PWM value.

In case of Hi-Res PWMs, the current implementation is capping the PWM
value at a 15-bit resolution, even when the lower resolutions are
selected.

Fix the issue by capping the PWM value to the maximum value allowed by
the selected resolution.

Cc: stable@vger.kernel.org # 6.4
Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM")
Reviewed-by: Bjorn Andersson <andersson@kernel.org>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
---
drivers/leds/rgb/leds-qcom-lpg.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c
index 4454fc6a38480b61916318dd170f3eddc32976d6..0b6310184988c299d82ee7181982c03d306407a4 100644
--- a/drivers/leds/rgb/leds-qcom-lpg.c
+++ b/drivers/leds/rgb/leds-qcom-lpg.c
@@ -530,7 +530,7 @@ static void lpg_calc_duty(struct lpg_channel *chan, uint64_t duty)
unsigned int clk_rate;

if (chan->subtype == LPG_SUBTYPE_HI_RES_PWM) {
- max = LPG_RESOLUTION_15BIT - 1;
+ max = BIT(lpg_pwm_resolution_hi_res[chan->pwm_resolution_sel]) - 1;
clk_rate = lpg_clk_rates_hi_res[chan->clk_sel];
} else {
max = BIT(lpg_pwm_resolution[chan->pwm_resolution_sel]) - 1;

--
2.34.1