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

From: Stephen Boyd
Date: Thu Dec 21 2017 - 21:15:26 EST

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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