linux-kernel - Re: [PATCH 0/3] Meson8b: add the CPU clock post-dividers

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Message-ID: <59801d61ba4e5d5fc8f0df1adffad1f9c7afb45c.camel@baylibre.com>
Date:   Thu, 22 Nov 2018 10:05:48 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-amlogic@...ts.infradead.org, narmstrong@...libre.com
Cc:     mturquette@...libre.com, sboyd@...nel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Meson8b: add the CPU clock post-dividers

On Fri, 2018-11-16 at 21:53 +0100, Martin Blumenstingl wrote:
> This is the successor to my previous series "meson8b: add the CPU_DIV16
> clock for the ARM TWD" from [0]. I decided to not send this as v2 of
> the original series because the PERIPH clock is not the CPU_DIV16 clock.
> It's not clear whether a CPU_DIV16 clock exists.
> 
> With this series we get all the CPU_CLK post-dividers as listed in the
> public S805 datasheet [1] on pages 31 and 32:
> - ABP
> - PERIPH (used as input for the ARM global timer and ARM TWD timer)
> - AXI
> - L2 DRAM
> 
> Each of these clocks has a register called "..._CLK_DIS" which is
> documented as a "just in case" bit:
> "Set to 1 to manually disable the [...] clock when changing the mux
> selection. Typically this bit is set to 0 since the clock muxes can
> switch without glitches."
> Since we're not supposed to touch that register we're setting
> CLK_IS_CRITICAL for these clocks in the driver.

If we are not supposed to touch the register, I'd prefer if you used RO ops
instead of using CLK_IS_CRITICAL.

> 
> The result of this is that we can use the PERIPH clock which clocks
> the ARM TWD timer. I will send a separate series to add the TWD timer.
> 
> 
> [0] http://lists.infradead.org/pipermail/linux-amlogic/2018-July/007890.html
> [1] 
> https://dn.odroid.com/S805/Datasheet/S805_Datasheet%20V0.8%2020150126.pdf
> 
> Martin Blumenstingl (3):
>   dt-bindings: clock: meson8b: export the CPU post dividers
>   clk: meson: meson8b: rename cpu_div2/cpu_div3 to
>     cpu_in_div2/cpu_in_div3
>   clk: meson: meson8b: add the CPU clock post divider clocks
> 
>  drivers/clk/meson/meson8b.c              | 268 ++++++++++++++++++++++-
>  drivers/clk/meson/meson8b.h              |  17 +-
>  include/dt-bindings/clock/meson8b-clkc.h |   4 +
>  3 files changed, 276 insertions(+), 13 deletions(-)
> 

With CLK_IS_CRITICAL removed, looks good to me:

Acked-by: Jerome Brunet <jbrunet@...libre.com>