linux-kernel - [PATCH v3 1/3] leds: rgb: leds-qcom-lpg: Fix pwm resolution max for normal PWMs

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Message-Id: <20250303-leds-qcom-lpg-fix-max-pwm-on-hi-res-v3-1-62703c0ab76a@linaro.org>
Date: Mon, 03 Mar 2025 13:52:50 +0200
From: Abel Vesa <abel.vesa@...aro.org>
To: Lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>, 
 Anjelique Melendez <anjelique.melendez@....qualcomm.com>
Cc: Uwe Kleine-König <ukleinek@...nel.org>, 
 Kamal Wadhwa <quic_kamalw@...cinc.com>, 
 Jishnu Prakash <jishnu.prakash@....qualcomm.com>, 
 Bjorn Andersson <andersson@...nel.org>, 
 Konrad Dybcio <konradybcio@...nel.org>, Johan Hovold <johan@...nel.org>, 
 Sebastian Reichel <sre@...nel.org>, Pavel Machek <pavel@....cz>, 
 linux-leds@...r.kernel.org, linux-pwm@...r.kernel.org, 
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Abel Vesa <abel.vesa@...aro.org>
Subject: [PATCH v3 1/3] leds: rgb: leds-qcom-lpg: Fix pwm resolution max
 for normal PWMs

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 normal PWMs (non Hi-Res), the current implementation is
capping the PWM value at a 9-bit resolution, even when the 6-bit
resolution is selected.

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

Fixes: 7a3350495d9a ("leds: rgb: leds-qcom-lpg: Add support for 6-bit PWM resolution")
Suggested-by: Anjelique Melendez <anjelique.melendez@....qualcomm.com>
Signed-off-by: Abel Vesa <abel.vesa@...aro.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 4e5c56ded1f0412c9913670699e912b24f3408bd..4454fc6a38480b61916318dd170f3eddc32976d6 100644
--- a/drivers/leds/rgb/leds-qcom-lpg.c
+++ b/drivers/leds/rgb/leds-qcom-lpg.c
@@ -533,7 +533,7 @@ static void lpg_calc_duty(struct lpg_channel *chan, uint64_t duty)
 		max = LPG_RESOLUTION_15BIT - 1;
 		clk_rate = lpg_clk_rates_hi_res[chan->clk_sel];
 	} else {
-		max = LPG_RESOLUTION_9BIT - 1;
+		max = BIT(lpg_pwm_resolution[chan->pwm_resolution_sel]) - 1;
 		clk_rate = lpg_clk_rates[chan->clk_sel];
 	}
 

-- 
2.34.1