linux-kernel - Re: [PATCH v4 02/10] clk: sunxi-ng: Mark AR100 clocks as critical

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Date:   Thu, 05 Sep 2019 11:56:03 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Samuel Holland <samuel@...lland.org>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Corentin Labbe <clabbe.montjoie@...il.com>,
        Vasily Khoruzhick <anarsoul@...il.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v4 02/10] clk: sunxi-ng: Mark AR100 clocks as critical

Quoting Maxime Ripard (2019-08-21 05:24:36)
> On Tue, Aug 20, 2019 at 08:02:55AM -0500, Samuel Holland wrote:
> > On 8/20/19 2:11 AM, Maxime Ripard wrote:
> > > So I'm not really sure that we should do it statically this way, and
> > > that we should do it at all.
> >
> > Do you have a better way to model "firmware uses this clock behind the scenes,
> > so Linux please don't touch it"? It's unfortunate that we have Linux and
> > firmware fighting over the R_CCU, but since we didn't have firmware (e.g. SCPI
> > clocks) in the beginning, it's where we are today.
> >
> > The AR100 clock doesn't actually have a gate, and it generally has dependencies
> > like R_INTC in use. So as I mentioned in the commit message, the clock will
> > normally be on anyway. The goal was to model the fact that there are users of
> > this clock that Linux doesn't/can't know about.
> 
> Like I said, if that's an option, I'd prefer to have protected-clocks
> work for everyone / for sunxi.
> 

Yes. Use protected-clocks to indicate what shouldn't be touched by the
kernel. It's not super easy to make it "generic" right now, but I
suppose we can work the flag into the core framework more so that we
still register the clks but otherwise make the 'clk_get()' operation
fail on them somehow and the disable unused operation skip them. I just
took the easy way out for qcom for the time being and didn't register
them from the driver.