linux-kernel - Re: [PATCH v2 4/6] dt: bindings: add mt7621-pll dt binding documentation

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Date:   Sun, 18 Aug 2019 10:29:29 +0800
From:   Chuanhong Guo <gch981213@...il.com>
To:     Oleksij Rempel <linux@...pel-privat.de>
Cc:     Rob Herring <robh@...nel.org>,
        "open list:COMMON CLK FRAMEWORK" <linux-clk@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        "open list:STAGING SUBSYSTEM" <devel@...verdev.osuosl.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        John Crispin <john@...ozen.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Weijie Gao <hackpascal@...il.com>, NeilBrown <neil@...wn.name>
Subject: Re: [PATCH v2 4/6] dt: bindings: add mt7621-pll dt binding documentation

Hi!

On Sun, Aug 18, 2019 at 2:06 AM Oleksij Rempel <linux@...pel-privat.de> wrote:
> >> SYSC_REG_CPLL_CLKCFG1 register is a clock gate controller. It is used to enable or disable clocks.
> >> Jist wild assumption. All peripheral devices are suing bus clock.
> >
> > This assumption is incorrect. When this patchset is applied in
> > OpenWrt, I asked the author why there's still a fixed clock in
> > mt7621.dtsi, He told me that there's another clock for those unchanged
> > peripherals and he doesn't have time to write a clock provider for it.
>
> Can you please provide a link to this patch or email.

This discussion is in Chinese and using an IM software so there's no
link available.

> We have at least 2 know registers:
> SYSC_REG_CPLL_CLKCFG0 - it provides some information about boostrapped
> refclock. PLL and dividers used for CPU and some sort of BUS (AHB?).
> SYSC_REG_CPLL_CLKCFG1 - a banch of gates to enable/disable clocks for
> all or some ip cores.
> What is probably missing is a set of dividers for
> each ip core. From your words it is not document.

The specific missing part I was referring to, is parent clocks for
every gates. I'm not going to assume this with current openwrt device
tree because some peripherals doesn't have a clock binding at all or
have a dummy one there.

>
> With this information the clk driver will provide gate functionality and
> a set of hardcoded clocks. With this driver will work part of power
> management and nice devicetree without fixed clocks.

Regards,
Chuanhong Guo