linux-kernel - Re: [PATCH] leds: rgb: leds-qcom-lpg: Only enable TRILED when LPG is used by LED

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Message-ID: <cc41233d-f270-4cbe-b355-64f4dcd0652d@oss.qualcomm.com>
Date: Mon, 17 Nov 2025 10:22:23 +0800
From: Fenglin Wu <fenglin.wu@....qualcomm.com>
To: Bjorn Andersson <andersson@...nel.org>
Cc: kernel@....qualcomm.com, Lee Jones <lee@...nel.org>,
        Pavel Machek <pavel@...nel.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Subbaraman Narayanamurthy <subbaraman.narayanamurthy@....qualcomm.com>,
        Pavel Machek <pavel@....cz>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] leds: rgb: leds-qcom-lpg: Only enable TRILED when LPG is
 used by LED


On 11/14/2025 10:56 PM, Bjorn Andersson wrote:
> On Fri, Nov 14, 2025 at 03:13:18PM +0800, Fenglin Wu wrote:
>> On 11/14/2025 12:58 PM, Bjorn Andersson wrote:
>>> If chan->in_use, then the channel is exposed as a LED and
>>> lpg_pwm_request() should have returned -EBUSY, so we should never reach
>>> lpg_pwm_apply()?
>> Yes, I agree.
>>
>> Change is trying to ignore enabling TRILED channel when the LPG channel
>> mapping to TRILED is not used for controlling the LED (not defining the LED
>> child nodes).
>>
>> So the fix should be just removing this line instead of adding the if check.
>>
> Sorry, it's been a while since I looked at this code, but isn't it
> possible to configure a channel going through the triled to be exposed
> as a PWM channel and if so, don't we need to enable the TRILED driver
> for this channel in those cases?

Yes, this is possible, and enabling TRILED is not necessary in this 
case. The signals from the LPG channels mapped to the TRILED channels 
can also be routed to the PMIC GPIOs by setting the GPIO pinctrl state 
to the "funcx" function. For example, for LPG channels in PMH0101, based 
on the PMIC GPIO usage table, these GPIOs can be used to output the PWM 
signals if they are configured to the "func1" function.

GPIO05 -- PWM1

GPIO06 -- PWM2

GPIO11 -- PWM3

GPIO08 -- PWM4

GPIO09 -- PWM4

>
>> I will update it in patch v2.
>>
>>> Why do you check chan->triled_mask? I guess we will still read/write the
>>> triled regiter, but don't make any changes if this is 0?
>>>
>>> Or is this the actual issue that you're fixing, that we read/write the
>>> registers when we shouldn't? If so this should be clarified in the
>>> commit message.
>> Yes, there was a case that a LPG channel mapping to TRILED is repurposed to
>> control a fan, and it was seen that the BOB1 (supplies to TRILED) voltage
>> bumped to higher voltage when the PWM channel was enabled.
>>
> Is the signal still routed through the TRILED, or is it muxed to another
> driver?
No, the signals will not be routed to TRILED but through other PMIC GPIOs.
>
> Regards,
> Bjorn
>
>>> Regards,
>>> Bjorn