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

Sebastian Reichel
2025-03-03T22:47:00Z

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Hi,

On Mon, Mar 03, 2025 at 01:52:51PM +0200, Abel Vesa wrote:
> 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>
> ---

Reviewed-by: Sebastian Reichel <sre@kernel.org>

Greetings,

-- Sebastian

> 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
>

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