[PATCH] arm64: dts: qcom: Add backlight support for eDP panel

[PATCH] arm64: dts: qcom: Add backlight support for eDP panel

[Yongxing Mou]

Previously, the eDP panel backlight was enabled via UEFI. Added backlight
control node in kernel DTS due to some meta may not enable the backlight.

Aligned with other x1e80100-based platforms: the PWM signal is controlled
by PMK8550, and the backlight enable signal is handled by PMC8380.

Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
---
 arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 ++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644
--- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
+++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
@@ -17,6 +17,16 @@ aliases {
 		serial1 = &uart14;
 	};
 
+	backlight: backlight {
+		compatible = "pwm-backlight";
+		pwms = <&pmk8550_pwm 0 5000000>;
+		enable-gpios = <&pmc8380_3_gpios 4 GPIO_ACTIVE_HIGH>;
+		power-supply = <&vreg_edp_bl>;
+
+		pinctrl-0 = <&edp_bl_en>, <&edp_bl_pwm>;
+		pinctrl-names = "default";
+	};
+
 	wcd938x: audio-codec {
 		compatible = "qcom,wcd9385-codec";
 
@@ -183,6 +193,22 @@ vreg_edp_3p3: regulator-edp-3p3 {
 		regulator-boot-on;
 	};
 
+	vreg_edp_bl: regulator-edp-bl {
+		compatible = "regulator-fixed";
+
+		regulator-name = "VBL9";
+		regulator-min-microvolt = <3600000>;
+		regulator-max-microvolt = <3600000>;
+
+		gpio = <&pmc8380_3_gpios 10 GPIO_ACTIVE_HIGH>;
+		enable-active-high;
+
+		pinctrl-names = "default";
+		pinctrl-0 = <&edp_bl_reg_en>;
+
+		regulator-boot-on;
+	};
+
 	vreg_nvme: regulator-nvme {
 		compatible = "regulator-fixed";
 
@@ -819,6 +845,8 @@ &mdss_dp3 {
 	aux-bus {
 		panel {
 			compatible = "edp-panel";
+
+			backlight = <&backlight>;
 			power-supply = <&vreg_edp_3p3>;
 
 			port {
@@ -879,6 +907,22 @@ usb0_1p8_reg_en: usb0-1p8-reg-en-state {
 	};
 };
 
+&pmc8380_3_gpios {
+	edp_bl_en: edp-bl-en-state {
+		pins = "gpio4";
+		function = "normal";
+		power-source = <1>;
+		input-disable;
+		output-enable;
+	};
+
+	edp_bl_reg_en: edp-bl-reg-en-state {
+		pins = "gpio10";
+		function = "normal";
+	};
+
+};
+
 &pmc8380_5_gpios {
 	usb0_pwr_1p15_reg_en: usb0-pwr-1p15-reg-en-state {
 		pins = "gpio8";
@@ -890,6 +934,17 @@ usb0_pwr_1p15_reg_en: usb0-pwr-1p15-reg-en-state {
 	};
 };
 
+&pmk8550_gpios {
+	edp_bl_pwm: edp-bl-pwm-state {
+		pins = "gpio5";
+		function = "func3";
+	};
+};
+
+&pmk8550_pwm {
+	status = "okay";
+};
+
 &smb2360_0 {
 	status = "okay";
 };

---
base-commit: f7d2388eeec24966fc4d5cf32d706f0514f29ac5
change-id: 20251028-hamoa_dvt_backlight-373528b7ce7e

Best regards,
-- 
Yongxing Mou <yongxing.mou@oss.qualcomm.com>

Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel

[Konrad Dybcio]

On 10/28/25 8:04 AM, Yongxing Mou wrote:
> Previously, the eDP panel backlight was enabled via UEFI. Added backlight
> control node in kernel DTS due to some meta may not enable the backlight.
> 
> Aligned with other x1e80100-based platforms: the PWM signal is controlled
> by PMK8550, and the backlight enable signal is handled by PMC8380.
> 
> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
> ---

The subject must say "hamoa-iot-evk:"
>  arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 ++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
> index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644
> --- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
> +++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
> @@ -17,6 +17,16 @@ aliases {
>  		serial1 = &uart14;
>  	};
>  
> +	backlight: backlight {
> +		compatible = "pwm-backlight";
> +		pwms = <&pmk8550_pwm 0 5000000>;

Try adjusting the backlight value.. you'll find some funny behavior
near the max level.. which reminds me I should send some fixes for
some laptop DTs

[...]

> +	vreg_edp_bl: regulator-edp-bl {
> +		compatible = "regulator-fixed";
> +
> +		regulator-name = "VBL9";
> +		regulator-min-microvolt = <3600000>;
> +		regulator-max-microvolt = <3600000>;
> +
> +		gpio = <&pmc8380_3_gpios 10 GPIO_ACTIVE_HIGH>;
> +		enable-active-high;
> +
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&edp_bl_reg_en>;

property-n
property-names

in this order, please

Konrad

Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel

[Yongxing Mou]

On 10/28/2025 5:08 PM, Konrad Dybcio wrote:
> On 10/28/25 8:04 AM, Yongxing Mou wrote:
>> Previously, the eDP panel backlight was enabled via UEFI. Added backlight
>> control node in kernel DTS due to some meta may not enable the backlight.
>>
>> Aligned with other x1e80100-based platforms: the PWM signal is controlled
>> by PMK8550, and the backlight enable signal is handled by PMC8380.
>>
>> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
>> ---
> 
> The subject must say "hamoa-iot-evk:"
Thanks and got it , will fix it in next version.>> 
arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 
++++++++++++++++++++++++++++++
>>   1 file changed, 55 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>> index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644
>> --- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>> +++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>> @@ -17,6 +17,16 @@ aliases {
>>   		serial1 = &uart14;
>>   	};
>>   
>> +	backlight: backlight {
>> +		compatible = "pwm-backlight";
>> +		pwms = <&pmk8550_pwm 0 5000000>;
> 
> Try adjusting the backlight value.. you'll find some funny behavior
> near the max level.. which reminds me I should send some fixes for
> some laptop DTs
> 
  I tried sliding the backlight between the maximum and minimum values. 
It seems that at a certain sliding speed, when approaching the maximum 
value, there is some brightness flickering. Is this the phenomenon 
you’re referring to?> [...]
> 
>> +	vreg_edp_bl: regulator-edp-bl {
>> +		compatible = "regulator-fixed";
>> +
>> +		regulator-name = "VBL9";
>> +		regulator-min-microvolt = <3600000>;
>> +		regulator-max-microvolt = <3600000>;
>> +
>> +		gpio = <&pmc8380_3_gpios 10 GPIO_ACTIVE_HIGH>;
>> +		enable-active-high;
>> +
>> +		pinctrl-names = "default";
>> +		pinctrl-0 = <&edp_bl_reg_en>;
> 
> property-n
> property-names
> 
> in this order, please
> 
> KonradThanks and got it ,will fix it in next version.

Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel

[Konrad Dybcio]

On 10/30/25 10:08 AM, Yongxing Mou wrote:
> 
> 
> On 10/28/2025 5:08 PM, Konrad Dybcio wrote:
>> On 10/28/25 8:04 AM, Yongxing Mou wrote:
>>> Previously, the eDP panel backlight was enabled via UEFI. Added backlight
>>> control node in kernel DTS due to some meta may not enable the backlight.
>>>
>>> Aligned with other x1e80100-based platforms: the PWM signal is controlled
>>> by PMK8550, and the backlight enable signal is handled by PMC8380.
>>>
>>> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
>>> ---
>>
>> The subject must say "hamoa-iot-evk:"
> Thanks and got it , will fix it in next version.>> arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 ++++++++++++++++++++++++++++++
>>>   1 file changed, 55 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>> index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644
>>> --- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>> +++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>> @@ -17,6 +17,16 @@ aliases {
>>>           serial1 = &uart14;
>>>       };
>>>   +    backlight: backlight {
>>> +        compatible = "pwm-backlight";
>>> +        pwms = <&pmk8550_pwm 0 5000000>;
>>
>> Try adjusting the backlight value.. you'll find some funny behavior
>> near the max level.. which reminds me I should send some fixes for
>> some laptop DTs
>>
>  I tried sliding the backlight between the maximum and minimum values. It seems that at a certain sliding speed, when approaching the maximum value, there is some brightness flickering. Is this the phenomenon you’re referring to?> [...]

"maybe" - for me it was the brightness actually going down beyond ~80%

The issue is that the PWM hardware can't really do a period that's
== 5000000 ns

But it seems like this is no longer an issue since the driver now
rounds up to the closest supported value, see last couple commits
to drivers/leds/rgb/leds-qcom-lpg.c

Konrad

Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel

[Yongxing Mou]

On 10/30/2025 5:41 PM, Konrad Dybcio wrote:
> On 10/30/25 10:08 AM, Yongxing Mou wrote:
>>
>>
>> On 10/28/2025 5:08 PM, Konrad Dybcio wrote:
>>> On 10/28/25 8:04 AM, Yongxing Mou wrote:
>>>> Previously, the eDP panel backlight was enabled via UEFI. Added backlight
>>>> control node in kernel DTS due to some meta may not enable the backlight.
>>>>
>>>> Aligned with other x1e80100-based platforms: the PWM signal is controlled
>>>> by PMK8550, and the backlight enable signal is handled by PMC8380.
>>>>
>>>> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
>>>> ---
>>>
>>> The subject must say "hamoa-iot-evk:"
>> Thanks and got it , will fix it in next version.>> arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 ++++++++++++++++++++++++++++++
>>>>    1 file changed, 55 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>> index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644
>>>> --- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>> +++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>> @@ -17,6 +17,16 @@ aliases {
>>>>            serial1 = &uart14;
>>>>        };
>>>>    +    backlight: backlight {
>>>> +        compatible = "pwm-backlight";
>>>> +        pwms = <&pmk8550_pwm 0 5000000>;
>>>
>>> Try adjusting the backlight value.. you'll find some funny behavior
>>> near the max level.. which reminds me I should send some fixes for
>>> some laptop DTs
>>>
>>   I tried sliding the backlight between the maximum and minimum values. It seems that at a certain sliding speed, when approaching the maximum value, there is some brightness flickering. Is this the phenomenon you’re referring to?> [...]
> 
> "maybe" - for me it was the brightness actually going down beyond ~80%
> 
> The issue is that the PWM hardware can't really do a period that's
> == 5000000 ns
> 
> But it seems like this is no longer an issue since the driver now
> rounds up to the closest supported value, see last couple commits
> to drivers/leds/rgb/leds-qcom-lpg.c
> 
> Konrad
Oh,thanks for sharing that. I saw the phenomenon you mentioned. 
Previously, my baseline had already merged this patch series: 
https://lore.kernel.org/all/20250305-leds-qcom-lpg-fix-max-pwm-on-hi-res-v4-0-bfe124a53a9f@linaro.org/, 
so I didn’t observe the ‘brightness actually going down beyond ~80%.’and 
just very slight flickering. After I reverted patches, it indeed 
appeared.  So here i want to confirm,
pwms = <&pmk8550_pwm 0 5000000>
can i keep the value 5000000 ?

Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel

[Konrad Dybcio]

On 10/30/25 12:07 PM, Yongxing Mou wrote:
> 
> 
> On 10/30/2025 5:41 PM, Konrad Dybcio wrote:
>> On 10/30/25 10:08 AM, Yongxing Mou wrote:
>>>
>>>
>>> On 10/28/2025 5:08 PM, Konrad Dybcio wrote:
>>>> On 10/28/25 8:04 AM, Yongxing Mou wrote:
>>>>> Previously, the eDP panel backlight was enabled via UEFI. Added backlight
>>>>> control node in kernel DTS due to some meta may not enable the backlight.
>>>>>
>>>>> Aligned with other x1e80100-based platforms: the PWM signal is controlled
>>>>> by PMK8550, and the backlight enable signal is handled by PMC8380.
>>>>>
>>>>> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
>>>>> ---
>>>>
>>>> The subject must say "hamoa-iot-evk:"
>>> Thanks and got it , will fix it in next version.>> arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 ++++++++++++++++++++++++++++++
>>>>>    1 file changed, 55 insertions(+)
>>>>>
>>>>> diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>>> index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644
>>>>> --- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>>> +++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>>> @@ -17,6 +17,16 @@ aliases {
>>>>>            serial1 = &uart14;
>>>>>        };
>>>>>    +    backlight: backlight {
>>>>> +        compatible = "pwm-backlight";
>>>>> +        pwms = <&pmk8550_pwm 0 5000000>;
>>>>
>>>> Try adjusting the backlight value.. you'll find some funny behavior
>>>> near the max level.. which reminds me I should send some fixes for
>>>> some laptop DTs
>>>>
>>>   I tried sliding the backlight between the maximum and minimum values. It seems that at a certain sliding speed, when approaching the maximum value, there is some brightness flickering. Is this the phenomenon you’re referring to?> [...]
>>
>> "maybe" - for me it was the brightness actually going down beyond ~80%
>>
>> The issue is that the PWM hardware can't really do a period that's
>> == 5000000 ns
>>
>> But it seems like this is no longer an issue since the driver now
>> rounds up to the closest supported value, see last couple commits
>> to drivers/leds/rgb/leds-qcom-lpg.c
>>
>> Konrad
> Oh,thanks for sharing that. I saw the phenomenon you mentioned. Previously, my baseline had already merged this patch series: https://lore.kernel.org/all/20250305-leds-qcom-lpg-fix-max-pwm-on-hi-res-v4-0-bfe124a53a9f@linaro.org/, so I didn’t observe the ‘brightness actually going down beyond ~80%.’and just very slight flickering. After I reverted patches, it indeed appeared.  So here i want to confirm,
> pwms = <&pmk8550_pwm 0 5000000>
> can i keep the value 5000000 ?

I think so.. perhaps make sure the period is appropriate for
the backlight device at the other end since you mentioned it's
flickering

Konrad

Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel

[Yongxing Mou]

On 10/30/2025 7:27 PM, Konrad Dybcio wrote:
> On 10/30/25 12:07 PM, Yongxing Mou wrote:
>>
>>
>> On 10/30/2025 5:41 PM, Konrad Dybcio wrote:
>>> On 10/30/25 10:08 AM, Yongxing Mou wrote:
>>>>
>>>>
>>>> On 10/28/2025 5:08 PM, Konrad Dybcio wrote:
>>>>> On 10/28/25 8:04 AM, Yongxing Mou wrote:
>>>>>> Previously, the eDP panel backlight was enabled via UEFI. Added backlight
>>>>>> control node in kernel DTS due to some meta may not enable the backlight.
>>>>>>
>>>>>> Aligned with other x1e80100-based platforms: the PWM signal is controlled
>>>>>> by PMK8550, and the backlight enable signal is handled by PMC8380.
>>>>>>
>>>>>> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
>>>>>> ---
>>>>>
>>>>> The subject must say "hamoa-iot-evk:"
>>>> Thanks and got it , will fix it in next version.>> arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 ++++++++++++++++++++++++++++++
>>>>>>     1 file changed, 55 insertions(+)
>>>>>>
>>>>>> diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>>>> index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644
>>>>>> --- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>>>> +++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>>>> @@ -17,6 +17,16 @@ aliases {
>>>>>>             serial1 = &uart14;
>>>>>>         };
>>>>>>     +    backlight: backlight {
>>>>>> +        compatible = "pwm-backlight";
>>>>>> +        pwms = <&pmk8550_pwm 0 5000000>;
>>>>>
>>>>> Try adjusting the backlight value.. you'll find some funny behavior
>>>>> near the max level.. which reminds me I should send some fixes for
>>>>> some laptop DTs
>>>>>
>>>>    I tried sliding the backlight between the maximum and minimum values. It seems that at a certain sliding speed, when approaching the maximum value, there is some brightness flickering. Is this the phenomenon you’re referring to?> [...]
>>>
>>> "maybe" - for me it was the brightness actually going down beyond ~80%
>>>
>>> The issue is that the PWM hardware can't really do a period that's
>>> == 5000000 ns
>>>
>>> But it seems like this is no longer an issue since the driver now
>>> rounds up to the closest supported value, see last couple commits
>>> to drivers/leds/rgb/leds-qcom-lpg.c
>>>
>>> Konrad
>> Oh,thanks for sharing that. I saw the phenomenon you mentioned. Previously, my baseline had already merged this patch series: https://lore.kernel.org/all/20250305-leds-qcom-lpg-fix-max-pwm-on-hi-res-v4-0-bfe124a53a9f@linaro.org/, so I didn’t observe the ‘brightness actually going down beyond ~80%.’and just very slight flickering. After I reverted patches, it indeed appeared.  So here i want to confirm,
>> pwms = <&pmk8550_pwm 0 5000000>
>> can i keep the value 5000000 ?
> 
> I think so.. perhaps make sure the period is appropriate for
> the backlight device at the other end since you mentioned it's
> flickering
> 
> Konrad
Compared to ‘brightness actually going down beyond ~80%’, this is just a 
very slight flicker that only occurs when sliding the brightness bar at 
a specific speed.It won’t occur in most cases. Also tried another value 
pwms = <&pmk8550_pwm 0 4266537>, and it looks the same, so can we keep 
it at 5000000 here?

Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel

[Konrad Dybcio]

On 11/5/25 10:58 AM, Yongxing Mou wrote:
> 
> 
> On 10/30/2025 7:27 PM, Konrad Dybcio wrote:
>> On 10/30/25 12:07 PM, Yongxing Mou wrote:
>>>
>>>
>>> On 10/30/2025 5:41 PM, Konrad Dybcio wrote:
>>>> On 10/30/25 10:08 AM, Yongxing Mou wrote:
>>>>>
>>>>>
>>>>> On 10/28/2025 5:08 PM, Konrad Dybcio wrote:
>>>>>> On 10/28/25 8:04 AM, Yongxing Mou wrote:
>>>>>>> Previously, the eDP panel backlight was enabled via UEFI. Added backlight
>>>>>>> control node in kernel DTS due to some meta may not enable the backlight.
>>>>>>>
>>>>>>> Aligned with other x1e80100-based platforms: the PWM signal is controlled
>>>>>>> by PMK8550, and the backlight enable signal is handled by PMC8380.
>>>>>>>
>>>>>>> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
>>>>>>> ---
>>>>>>
>>>>>> The subject must say "hamoa-iot-evk:"
>>>>> Thanks and got it , will fix it in next version.>> arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 ++++++++++++++++++++++++++++++
>>>>>>>     1 file changed, 55 insertions(+)
>>>>>>>
>>>>>>> diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>>>>> index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644
>>>>>>> --- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>>>>> +++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
>>>>>>> @@ -17,6 +17,16 @@ aliases {
>>>>>>>             serial1 = &uart14;
>>>>>>>         };
>>>>>>>     +    backlight: backlight {
>>>>>>> +        compatible = "pwm-backlight";
>>>>>>> +        pwms = <&pmk8550_pwm 0 5000000>;
>>>>>>
>>>>>> Try adjusting the backlight value.. you'll find some funny behavior
>>>>>> near the max level.. which reminds me I should send some fixes for
>>>>>> some laptop DTs
>>>>>>
>>>>>    I tried sliding the backlight between the maximum and minimum values. It seems that at a certain sliding speed, when approaching the maximum value, there is some brightness flickering. Is this the phenomenon you’re referring to?> [...]
>>>>
>>>> "maybe" - for me it was the brightness actually going down beyond ~80%
>>>>
>>>> The issue is that the PWM hardware can't really do a period that's
>>>> == 5000000 ns
>>>>
>>>> But it seems like this is no longer an issue since the driver now
>>>> rounds up to the closest supported value, see last couple commits
>>>> to drivers/leds/rgb/leds-qcom-lpg.c
>>>>
>>>> Konrad
>>> Oh,thanks for sharing that. I saw the phenomenon you mentioned. Previously, my baseline had already merged this patch series: https://lore.kernel.org/all/20250305-leds-qcom-lpg-fix-max-pwm-on-hi-res-v4-0-bfe124a53a9f@linaro.org/, so I didn’t observe the ‘brightness actually going down beyond ~80%.’and just very slight flickering. After I reverted patches, it indeed appeared.  So here i want to confirm,
>>> pwms = <&pmk8550_pwm 0 5000000>
>>> can i keep the value 5000000 ?
>>
>> I think so.. perhaps make sure the period is appropriate for
>> the backlight device at the other end since you mentioned it's
>> flickering
>>
>> Konrad
> Compared to ‘brightness actually going down beyond ~80%’, this is just a very slight flicker that only occurs when sliding the brightness bar at a specific speed.It won’t occur in most cases. Also tried another value pwms = <&pmk8550_pwm 0 4266537>, and it looks the same, so can we keep it at 5000000 here?

As I said, just put whatever the backlight that the PWM controller
outputs to expects.

Konrad