linux-kernel - Re: [PATCH 08/10] power: supply: rt5033_charger: Make use of high impedance mode

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Message-ID: <688277f8-c6e4-6e9b-2f56-01a63103e61d@rocketmail.com>
Date:   Sun, 2 Apr 2023 12:14:03 +0200
From:   Jakob Hauser <jahau@...ketmail.com>
To:     Sebastian Reichel <sre@...nel.org>
Cc:     Lee Jones <lee@...nel.org>, Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Beomho Seo <beomho.seo@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Stephan Gerhold <stephan@...hold.net>,
        Raymond Hackley <raymondhackley@...tonmail.com>,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH 08/10] power: supply: rt5033_charger: Make use of high
 impedance mode

Hi Sebastian,

On 28.02.23 23:32, Jakob Hauser wrote:
> Enable high impedance mode to reduce power consumption. However, it needs to be
> disabled in case of charging or OTG mode.
> 
> Tested-by: Raymond Hackley <raymondhackley@...tonmail.com>
> Signed-off-by: Jakob Hauser <jahau@...ketmail.com>
> ---
>   drivers/power/supply/rt5033_charger.c | 47 ++++++++++++++++++++++++++-
>   1 file changed, 46 insertions(+), 1 deletion(-)

...

Raymond (in copy) did some tests on the flash LEDs, which are also 
managed by the rt5033 chip. There is no driver for leds-rt5033 yet but 
Raymond got the rt5033 LEDs running via the similar driver leds-sgm3140.

However, to get the flash LEDs working, he had to disable the high 
impedance mode of rt5033.

I implemented the use of high impedance mode by this patch to improve 
power saving. It's kind of a sleep mode. Although it's not clear how 
much power it does save, it's generally worth trying to improve power 
saving on mobile devices as far as possible.

As it now turns out that the use of high impedance mode might complicate 
the handling of the flash LEDs, I would drop this patch in the next 
version v2 of the patchset. Let's skip this power saving attempt for 
now. It still can be added at a later date as an improvement.

Kind regards,
Jakob