linux-kernel - Re: [PATCH v2 0/3] clk: meson: rounding for fast clocks on 32-bit SoCs

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Message-ID: <162439665901.1026800.14766697980134538910@swboyd.mtv.corp.google.com>
Date:   Tue, 22 Jun 2021 14:17:39 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Neil Armstrong <narmstrong@...libre.com>, mturquette@...libre.com,
        khilman@...libre.com, linux-kernel@...r.kernel.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 0/3] clk: meson: rounding for fast clocks on 32-bit SoCs

Quoting Martin Blumenstingl (2021-06-22 14:04:55)
> Hi Stephen,
> 
> On Mon, Jun 7, 2021 at 9:04 AM Jerome Brunet <jbrunet@...libre.com> wrote:
> >
> >
> > On Fri 04 Jun 2021 at 19:18, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:
> >
> > > Hi Jerome, Hi Stephen,
> > >
> > > On Mon, May 24, 2021 at 12:37 PM Martin Blumenstingl
> > > <martin.blumenstingl@...glemail.com> wrote:
> > >>
> > >> On the 32-bit Amlogic Meson8/8b/8m2 SoCs we run into a problem with the
> > >> fast HDMI PLL and it's OD (post-dividers). This clock tree can run at
> > >> up to approx. 3GHz.
> > >> This however causes a problem, because these rates require BIT(31) to
> > >> be usable. Unfortunately this is not the case with clk_ops.round_rate
> > >> on 32-bit systems. BIT(31) is reserved for the sign (+ or -).
> > >>
> > >> clk_ops.determine_rate does not suffer from this limitation. It uses
> > >> an int to signal any errors and can then take all availble 32 bits for
> > >> the clock rate.
> > >>
> > >> Changes since v1 from [0]:
> > >> - reworked the first patch so the the existing
> > >>   divider_{ro_}round_rate_parent implementations are using the new
> > >>   divider_{ro_}determine_rate implementations to avoid code duplication
> > >>   (thanks Jerome for the suggestion)
> > >> - added a patch to switch the default clk_divider_{ro_}ops to use
> > >>   .determine_rate instead of .round_rate as suggested by Jerome
> > >>   (thanks)
> > >> - dropped a patch for the Meson PLL ops as these are independent from
> > >>   the divider patches and Jerome has applied that one directly (thanks)
> > >> - added Jerome's Reviewed-by to the meson clk-regmap patch (thanks!)
> > >> - dropped the RFC prefix
> > > please let me know what you think about this v2
> > > I am asking because clk-divider is widely used, so I'd appreciate if
> > > this gets some time in linux-next (so for example Kernel CI can test
> > > this and report issues if there are any).
> Do you have any comments on this series?
> I am fine with it skipping 5.14 as it's a change which affects
> multiple platforms.
> So I would like to use the time until the trees are opening for
> patches targeting 5.15 to iron out code-review comments.
> 
> > Looks good to me
> > Reviewed-by: Jerome Brunet <jbrunet@...libre.com>
> Thanks Jerome - I'll add it to v3 once I send it (assuming nothing
> major changes)

Looks ok to me. Will you resend?