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Date:   Mon, 11 Nov 2019 08:17:17 +0000
From:   Lee Jones <lee.jones@linaro.org>
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     linux-kernel@vger.kernel.org, arm@kernel.org,
        Stephan Gerhold <stephan@gerhold.net>
Subject: Re: [PATCH v3] mfd: db8500-prcmu: Support U8420-sysclk firmware
Message-ID: <20191111081717.GG18902@dell>
References: <20191026214732.17725-1-linus.walleij@linaro.org>
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On Sat, 26 Oct 2019, 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@kernel.org
> Cc: Lee Jones <lee.jones@linaro.org>
> Cc: Stephan Gerhold <stephan@gerhold.net>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - It's a bad idead to return -ENODEV in a function
>   that returns void.
> ChangeLog v1->v2:
> - Change the style of the ULPPLL check function (more
>   compact)
> - Fix a missing of_node_put() by actually returning
>   with -ENODEV on error.
> 
> ARM SoC folks: as this mostly affects the MFD subsystems
> I think it'd be best if Lee can merge it, I do not
> plan any other changes to the ARM core files that the
> patch touches.
> ---
>  arch/arm/mach-ux500/cpu-db8500.c |  2 +-
>  drivers/mfd/db8500-prcmu.c       | 63 ++++++++++++++++++++++----------
>  include/linux/mfd/db8500-prcmu.h |  4 +-
>  include/linux/mfd/dbx500-prcmu.h |  7 ++--
>  4 files changed, 50 insertions(+), 26 deletions(-)

Applied, thanks.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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