linux-kernel - Re: [PATCH] arm64: dts: qcom: msm8916/39-samsung-a2015: Add flash LED

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Message-ID: <ZOz4460Q/JQcMcU1@L14.lan>
Date:   Mon, 28 Aug 2023 21:43:56 +0200
From:   Henrik Grimler <henrik@...mler.se>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Raymond Hackley <raymondhackley@...tonmail.com>, agross@...nel.org,
        andersson@...nel.org, conor+dt@...nel.org,
        devicetree@...r.kernel.org, krzysztof.kozlowski+dt@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        nikita@...n.ru, robh+dt@...nel.org, stephan@...hold.net,
        ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH] arm64: dts: qcom: msm8916/39-samsung-a2015: Add flash LED

Hi Konrad,

On Sat, Aug 26, 2023 at 02:09:38PM +0200, Konrad Dybcio wrote:
> On 22.08.2023 17:01, Raymond Hackley wrote:
> > Hi Konrad,
> > 
> >> What about the other subdevices registered with the RT5033 MFD?
> > 
> > Currently the MFD is not able to control the flash LED, due to missing
> > driver for it.
> > Alternatively we control it with GPIO pins. With driver leds-sgm3140, the
> > binding is not under the RT5033 MFD.
> Hm.. I have mixed feelings..
> 
> Does the led controlled onboard this chip have some super complex
> functionality that is going to be exposed through a specific driver
> and that is not exposed through the sgm3140 driver?

The rt5033-led&sgm3140 situation was discussed in msm8916-mainline
matrix room before, here is a summary for list.

Using the full rt5033-led driver (old patchset here [1]) has some
benefits, like:
* led can have different intensity levels
* led can (supposedly) be used in strobe mode

Using sgm3140 driver mostly works fine, but there could potentially be
situations where led stops working and a reboot to stock android
kernel is required to get it working again.  So far that has only been
reproduced by first booting a kernel with full rt5033-led driver
(based on [1]), and then booting a kernel using sgm3140 driver
instead.

[1] https://lore.kernel.org/linux-leds/1448446948-13729-1-git-send-email-ingi2.kim@samsung.com/

Best regards,
Henrik Grimler