linux-kernel - Re: [PATCH] arm64: dts: qcom: hamoa-iot-evk: enable pwm rgb leds

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Message-ID: <nepbosujmpldx5exylkqjylonntj6v3p4jnnoyxstmbmilb7jc@t65dwpxzorg7>
Date: Sat, 25 Oct 2025 22:15:49 -0500
From: Bjorn Andersson <andersson@...nel.org>
To: Tingguo Cheng <tingguo.cheng@....qualcomm.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>, 
	Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, kernel@....qualcomm.com, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Kamal Wadhwa <kamal.wadhwa@....qualcomm.com>, Rakesh Kota <rakesh.kota@....qualcomm.com>, 
	Fenglin Wu <fenglin.wu@....qualcomm.com>
Subject: Re: [PATCH] arm64: dts: qcom: hamoa-iot-evk: enable pwm rgb leds

On Tue, Oct 21, 2025 at 02:29:22PM +0800, Tingguo Cheng wrote:
> 
> On 10/17/2025 4:09 PM, Konrad Dybcio wrote:
> > On 10/17/25 10:06 AM, Tingguo Cheng wrote:
> > > Add red, green and blue LED channels for the RGB device connected to
> > > PMC8380C PWM-LED pins.
> > > 
> > > Signed-off-by: Tingguo Cheng<tingguo.cheng@....qualcomm.com>
> > > ---
> > Just to make sure, is this a "multicolor LED" consisting of 3 ones,
> > and *not* three LEDs that are supposed to communicate different
> > functions (i.e. network, power, disk i/o)?
> Yes, it's a multicolor LED composed of three individual LEDs within a single
> package—not three separate LEDs for different functions like network, power,
> or disk I/O.
> However, there's one exception worth mentioning:
> The blue channel is connected to two sourcing signals—the EDL indicator and
> the PMIC PWM-RGB blue LED—via two resistors. These resistors allow selection
> between the two sources.
> By default, the board is configured with the resistor soldered to connect
> the blue LED to the EDL indicator.
> To support software control, I’ve added the blue channel in the DTS,
> enabling the capability to light the blue LED from the software side.
> Some developers may choose to re-solder the resistor to connect the blue LED
> to the PMIC PWM-RGB output instead, depending on their hardware setup.

Sounds like we have a RG LED, and if the user chooses to modify their
hardware, they have different hardware...which they can easily describe
by updating their DeviceTree.


It's a bit weird, but does it work to make this LED_COLOR_ID_MULTI with
just the RED and GREEN channels described?

Regards,
Bjorn

> > Konrad