linux-kernel - Re: [PATCH v5 00/10] clk: implement clock rate protection mechanism

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Message-ID: <20171222021520.GO7997@codeaurora.org>
Date:   Thu, 21 Dec 2017 18:15:20 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Michael Turquette <mturquette@...libre.com>
Cc:     Jerome Brunet <jbrunet@...libre.com>, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Quentin Schulz <quentin.schulz@...e-electrons.com>,
        Kevin Hilman <khilman@...libre.com>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH v5 00/10] clk: implement clock rate protection mechanism

On 12/19, Michael Turquette wrote:
> Quoting Jerome Brunet (2017-12-01 13:51:50)
> > This Patchset is related the RFC [0] and the discussion around
> > CLK_SET_RATE_GATE available here [1]
> > 
> > This patchset introduce clock protection to the CCF core. This can then
> > be used for:
> > 
> > * Provide a way for a consumer to claim exclusivity over the rate control
> >   of a provider. Some clock consumers require that a clock rate must not
> >   deviate from its selected frequency. There can be several reasons for
> >   this, not least of which is that some hardware may not be able to
> >   handle or recover from a glitch caused by changing the clock rate while
> >   the hardware is in operation. For such HW, The ability to get exclusive
> >   control of a clock's rate, and release that exclusivity, could be seen
> >   as a fundamental clock rate control primitive. The exclusivity is not
> >   preemptible, so when claimed more than once, is rate is effectively
> >   locked.
> > 
> > * Provide a similar functionality to providers themselves, fixing
> >   CLK_SET_RATE_GATE flag (enforce clock gating along the tree). While
> >   there might still be a few platforms relying the broken implementation,
> >   tests done has shown this change to be pretty safe.
> 
> Applied to clk-protect-rate, with the exception that I did not apply
> "clk: fix CLK_SET_RATE_GATE with clock rate protection" as it breaks
> qcom clk code.
> 
> Stephen, do you plan to fix up the qcom clock code so that the
> SET_RATE_GATE improvement can go in?
> 

I started working on it a while back. Let's see if I can finish
it off this weekend.

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