linux-kernel - Re: [PATCH V5 11/18] clk: tegra210: Add support for Tegra210 clocks

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Message-ID: <ab8f2441-8f4b-3a2b-5bcd-1a889555176a@nvidia.com>
Date:   Thu, 18 Jul 2019 10:22:27 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>
CC:     Peter De Schrijver <pdeschrijver@...dia.com>,
        Joseph Lo <josephl@...dia.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <tglx@...utronix.de>,
        <jason@...edaemon.net>, <marc.zyngier@....com>,
        <linus.walleij@...aro.org>, <stefan@...er.ch>,
        <mark.rutland@....com>, <pgaikwad@...dia.com>,
        <linux-clk@...r.kernel.org>, <linux-gpio@...r.kernel.org>,
        <jckuo@...dia.com>, <talho@...dia.com>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <mperttunen@...dia.com>, <spatra@...dia.com>, <robh+dt@...nel.org>,
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH V5 11/18] clk: tegra210: Add support for Tegra210 clocks


On 7/18/19 9:34 AM, Dmitry Osipenko wrote:
> 18.07.2019 4:15, Sowjanya Komatineni пишет:
>
> [snip]
>
>>>> Please try to fix all missing dependencies and orderings.
>>> Peter,
>>>
>>> dfllCPU_OUT is the first one to go thru restore when
>>> clk_restore_context traverses thru the list.
>>>
>>> dfllCPU_OUT has dependency on DFLL_ref and DFLL_SOC but this
>>> dependency is unknown to clock-tree.
>>>
>>> We can add DFLL_REF and DFLL_SOC as parents to dfllCPU_OUT during
>>> register so dfllCPU_OUT save/restore happens after their parents are
>>> restored.
>>>
>>> But DFLL needs both of these to be restored before DFLLCPU_Out and as
>>> DFLL_SOC restore always happens after the REF, thinking to add
>>> DFLL_SOC as parent to dfllCPU_OUT so save/restore follows after their
>>> dependencies.
>>>
>>> Please comment.
>>>
>> Did quick try and I see by adding dfll-soc as parent to dfllCPU_OUT, its
>> in proper order after all its dependencies.
>>
>> Can now add dfll save/restore to do dfll reinit during restore..
>>
> If dfllCPU_OUT can work properly with dfll-soc being disabled, then this
> kind of dependency isn't very correct and just papers over the real
> problem, which is that there should be a way for CCF to specify multiple
> dependencies for the clock or the reverse ordering should be used for
> the restoring.

dfll will not work without dfll-soc enabled.

CLDVFS control logic is split into 2 clock domains. dvfs_ref_clk and 
dvfs_soc_clk.

Majority of the control logic is clocked from dvfs_soc_clk for 
interfacing control registers.