linux-kernel - Re: [PATCH v3] mfd: db8500-prcmu: Support U8420-sysclk firmware

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Date:   Mon, 28 Oct 2019 11:00:45 -0700
From:   Olof Johansson <olof@...om.net>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ARM-SoC Maintainers <arm@...nel.org>,
        Stephan Gerhold <stephan@...hold.net>
Subject: Re: [PATCH v3] mfd: db8500-prcmu: Support U8420-sysclk firmware

On Mon, Oct 28, 2019 at 9:00 AM Olof Johansson <olof@...om.net> wrote:
>
> On Sat, Oct 26, 2019 at 11:47:32PM +0200, Linus Walleij wrote:
> > There is a distinct version of the Ux500 U8420 variant
> > with "sysclk", as can be seen from the vendor code that
> > didn't make it upstream, this firmware lacks the
> > ULPPLL (ultra-low power phase locked loop) which in
> > effect means that the timer clock is instead wired to
> > the 32768 Hz always-on clock.
> >
> > This has some repercussions when enabling the timer
> > clock as the code as it stands will disable the timer
> > clock on these platforms (lacking the so-called
> > "doze mode") and obtaining the wrong rate of the timer
> > clock.
> >
> > The timer frequency is of course needed very early in
> > the boot, and as a consequence, we need to shuffle
> > around the early PRCMU init code: whereas in the past
> > we did not need to look up the PRCMU firmware version
> > in the early init, but now we need to know the version
> > before the core system timers are registered so we
> > restructure the platform callbacks to the PRCMU so as
> > not to take any arguments and instead look up the
> > resources it needs directly from the device tree
> > when initializing.
> >
> > As we do not yet support any platforms using this
> > firmware it is not a regression, but as PostmarketOS
> > is starting to support products with this firmware we
> > need to fix this up.
> >
> > The low rate of 32kHz also makes the MTU timer unsuitable
> > as delay timer but this needs to be fixed in a separate
> > patch.
> >
> > Cc: arm@...nel.org
> > Cc: Lee Jones <lee.jones@...aro.org>
> > Cc: Stephan Gerhold <stephan@...hold.net>
> > Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
>
>
> Fine with me to go through MTD, so:

s/MTD/MFD/g

>
> Acked-by: Olof Johansson <olof@...om.net>
>
>
> -Olof