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From:   Nylon Chen <nylon.chen@sifive.com>
Date:   Fri, 4 Aug 2023 09:42:06 +0800
Message-ID: <CAHh=Yk9A3MP4Zgz53+s_ugvMtnv57igY=+Yccbp9Om9jBuxXqg@mail.gmail.com>
Subject: Re: [PATCH v4 0/1] Change PWM-controlled LED pin active mode and algorithm
To:     Conor Dooley <conor.dooley@microchip.com>
Cc:     linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        linux-riscv@lists.infradead.org, geert+renesas@glider.be,
        pavel@ucw.cz, vincent.chen@sifive.com,
        emil.renner.berthing@canonical.com, aou@eecs.berkeley.edu,
        palmer@dabbelt.com, paul.walmsley@sifive.com,
        krzysztof.kozlowski+dt@linaro.org, robh+dt@kernel.org,
        conor@kernel.org, zong.li@sifive.com
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Hi Conor,

Conor Dooley <conor.dooley@microchip.com> =E6=96=BC 2023=E5=B9=B48=E6=9C=88=
3=E6=97=A5 =E9=80=B1=E5=9B=9B =E4=B8=8B=E5=8D=885:44=E5=AF=AB=E9=81=93=EF=
=BC=9A
>
> Hey Nylon,
>
> (I yoinked the reply to 1/1 to here, as it makes more sense in this
> context)
>
> > On Thu, Aug 03, 2023 at 10:15:10AM +0100, Conor Dooley wrote:
> > > On Thu, Aug 03, 2023 at 04:57:33PM +0800, Nylon Chen wrote:
> > > > According to the circuit diagram of User LEDs - RGB described in th=
emanual hifive-unleashed-a00.pdf[0] and hifive-unmatched-schematics-v3.pdf[=
1].
> > > >
> > > > The behavior of PWM is acitve-high.
> > > >
> > > > Removed patches: 1
> > > > New patches: (none)
> > > >
> > > > Links:
> > > > - [0]:  https://sifive.cdn.prismic.io/sifive/c52a8e32-05ce-4aaf-95c=
8-7bf8453f8698_hifive-unleashed-a00-schematics-1.pdf
> > > > - [1]:  https://sifive.cdn.prismic.io/sifive/6a06d6c0-6e66-49b5-8e9=
e-e68ce76f4192_hifive-unmatched-schematics-v3.pdf
> > > > - [2]:  https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d=
8-86ed8b16acba_fu740-c000-manual-v1p6.pdf
> > > >
> > > > Changed in v4:
> > > >  - Remove previous updates to the PWM algorithm.
> > >
> > > Why? I don't recall the conclusion on the previous version being that
> > > that patch was not needed.
> >
> > I apologize for forgetting about this update earlier. Just now,
> > I tried to pull rebase master and noticed that other developers seem
> > to have made some fixes to the algorithm. Upon closer inspection, I
> > found that they addressed the part we previously discussed with Emil
> > and Uwe, such as "first pwm_apply_state."
> >
> > Therefore, my instinct tells me that they have already taken care of
> > the issues we discussed before.
>
> I didn't see anything in linux-next that would solve this problem of
> inversion. The last meaningful change is:
>         commit 334c7b13d38321e47d1a51dba0bef9f4c403ec75
>         Author:     Emil Renner Berthing <emil.renner.berthing@canonical.=
com>
>         AuthorDate: Wed Nov 9 12:37:24 2022 +0100
>         Commit:     Thierry Reding <thierry.reding@gmail.com>
>         CommitDate: Mon Jan 30 16:42:45 2023 +0100
>
>             pwm: sifive: Always let the first pwm_apply_state succeed
>
> which predates your v3 by quite a bit.
>
> > I will review the conflicting parts in the pwm-sifive.c code in my v4
> > version once again to ensure there are no omissions. If I find any, I
> > will submit v5 accordingly.
>
> And if this patch is okay in isolation, please reply here explaining
> which commit fixed the algorithm, so that I can pick it up.
This patch needs to be accompanied by modifications to the
pwm_sifive_apply() function to make sense.

I will double-check and review the previous discussions to ensure
that. Thank you for your response.
>
> Thanks,
> Conor.