linux-kernel - Re: [PATCH v2 1/5] dt-bindings: update device tree binding for Allwinner PRCM CCUs

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Message-ID: <20170322200923.tcr7yqnfqj2zk2v7@lukather>
Date:   Wed, 22 Mar 2017 21:09:23 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Icenowy Zheng <icenowy@...c.xyz>
Cc:     Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-sunxi@...glegroups.com" <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH v2 1/5] dt-bindings: update device tree binding for
 Allwinner PRCM CCUs

On Wed, Mar 22, 2017 at 02:22:22AM +0800, Icenowy Zheng wrote:
> 
> 
> 21.03.2017, 15:41, "Maxime Ripard" <maxime.ripard@...e-electrons.com>:
> > On Thu, Mar 16, 2017 at 01:28:04AM +0800, Icenowy Zheng wrote:
> >>  Many Allwinner SoCs after A31 have a CCU in PRCM block.
> >>
> >>  Give the ones on H3 and A64 compatible strings.
> >>
> >>  Signed-off-by: Icenowy Zheng <icenowy@...c.xyz>
> >>  ---
> >>  Changes in v2:
> >>  - Add iosc for R_CCU's on H3/A64. (A31, A23 and A33 seem to have different
> >>    clock for mux 3 of ar100 clk. Investgations are needed for them.)
> >>
> >>   Documentation/devicetree/bindings/clock/sunxi-ccu.txt | 18 +++++++++++++++++-
> >>   1 file changed, 17 insertions(+), 1 deletion(-)
> >>
> >>  diff --git a/Documentation/devicetree/bindings/clock/sunxi-ccu.txt b/Documentation/devicetree/bindings/clock/sunxi-ccu.txt
> >>  index 68512aa398a9..4a4addff595d 100644
> >>  --- a/Documentation/devicetree/bindings/clock/sunxi-ccu.txt
> >>  +++ b/Documentation/devicetree/bindings/clock/sunxi-ccu.txt
> >>  @@ -7,9 +7,11 @@ Required properties :
> >>                   - "allwinner,sun8i-a23-ccu"
> >>                   - "allwinner,sun8i-a33-ccu"
> >>                   - "allwinner,sun8i-h3-ccu"
> >>  + - "allwinner,sun8i-h3-r-ccu"
> >>                   - "allwinner,sun8i-v3s-ccu"
> >>                   - "allwinner,sun9i-a80-ccu"
> >>                   - "allwinner,sun50i-a64-ccu"
> >>  + - "allwinner,sun50i-a64-r-ccu"
> >>                   - "allwinner,sun50i-h5-ccu"
> >>
> >>   - reg: Must contain the registers base address and length
> >>  @@ -20,7 +22,11 @@ Required properties :
> >>   - #clock-cells : must contain 1
> >>   - #reset-cells : must contain 1
> >>
> >>  -Example:
> >>  +For the PRCM CCUs on H3/A64, one more clock is needed:
> >>  +- "iosc": another frequency oscillator used for CPUS (usually at 32000Hz,
> >>  + not the same with losc)
> >
> > This is called the internal oscillator in the datasheet, it would
> > probably make more sense to call it that way in the documentation too.
> >
> > This oscillator seems to be clocked at 16MHz, so we should represent
> > it as such.
> >
> > And I'm wondering, are you *sure* that it's fed directly from the
> > internal oscillator, or goes through the registers in the RTC, with
> > the 32 divider and 16 prescaler by default that makes it at roughly
> > the same rate (31.25kHz).
> 
> In fact I know nothing about it -- I only represented the code in BSP
> clock driver.
> 
> The mux value 3 varies from SoC to SoC. For A64/H5 it's 32000,
> for A33 it's 667000 (seems to be directly the internal OSC, as the
> user manual says the internal OSC is 600~700kHz; but it's named
> cpuosc rather than iosc in A33 BSP clock driver); for A80 it's even
> PLL_AUDIO.

Where are you getting those info from?

As far as I know, the A33 PRCM takes the hosc, losc, pll6 and CPU
(internal) oscillator:
https://github.com/allwinner-zh/linux-3.4-sunxi/blob/master/drivers/clk/sunxi/clk-sun8iw5.c#L508

The H3 takes the hosc and losc:
https://github.com/allwinner-zh/linux-3.4-sunxi/blob/master/drivers/clk/sunxi/clk-sun8iw7.c#L379

The A80 takes the hosc and losc:
https://github.com/allwinner-zh/linux-3.4-sunxi/blob/master/drivers/clk/sunxi/clk-sun9iw1.c#L281

The A64 takes the hosc, losc, pll-periph0 and the iosc, which indeed
seems to be fed from the internal oscillator with the divider in the
RTC:
https://github.com/longsleep/linux-pine64/blob/lichee-dev-v3.10.65-bsp2.0/arch/arm64/boot/dts/sun50iw1p1-clk.dtsi#L19
https://github.com/longsleep/linux-pine64/blob/lichee-dev-v3.10.65-bsp2.0/drivers/clk/sunxi/clk-sun50iw1.c#L603

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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