linux-kernel - Re: [PATCH v2 2/2] clk: tegra: divider: Support enable-bit for Super clocks

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Message-ID: <74ee0e7f-c257-8fdf-bf3f-eefab3281dfa@gmail.com>
Date:   Tue, 29 Oct 2019 16:20:36 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Peter De Schrijver <pdeschrijver@...dia.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] clk: tegra: divider: Support enable-bit for Super
 clocks

28.10.2019 17:41, Peter De Schrijver пишет:
> On Tue, Jul 23, 2019 at 05:52:45AM +0300, Dmitry Osipenko wrote:
>> All Super clocks have a divider that has the enable bit.
>>
> 
> This is broken to begin with. The only clock of this type in upstream is SCLK
> I think. However, this clock is not a normal divider, it's a skipper, so
> the normal divider logic doesn't work for it. In practice this clock is
> only used when scaling SCLK, which is not (yet) done in the upstream
> kernel due to the complex DVFS relationship between sclk, hclk and pclk.
> A driver for it can be found here:
> https://nv-tegra.nvidia.com/gitweb/?p=linux-4.9.git;a=blob;f=drivers/clk/tegra/clk-skipper.c;h=f5da4f6ca44fe194c87f66be70c708e9791db74d;hb=eb8dd21affa2be45fc29be8c082194ac4032393a
> As you can see in that tree, we eventually splitted sclk into three
> clocks:
> 
> sclk_mux (controls SCLK_BURST_POLICY register)
> sclk (controls SOURCE_SYS register which is like a normal peripheral
> clock but without the mux)
> sclk_skipper (controls SCLK_DIVIDER)

I'll drop this patch, thanks again for the clarification.