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Date: Thu, 18 Feb 2016 18:03:33 -0800 From: Stephen Boyd <sboyd@...eaurora.org> To: Michael Turquette <mturquette@...libre.com> Cc: linux-clk@...r.kernel.org, lee.jones@...aro.org, maxime.ripard@...e-electrons.com, maxime.coquelin@...com, geert@...ux-m68k.org, heiko@...ech.de, andre.przywara@....com, rklein@...dia.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH v42 1/6] clk: Allow clocks to be marked as CRITICAL On 02/15, Michael Turquette wrote: > Quoting Stephen Boyd (2016-02-12 17:14:03) > > On 02/11, Michael Turquette wrote: > > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > > > index b4db67a..993f775 100644 > > > --- a/drivers/clk/clk.c > > > +++ b/drivers/clk/clk.c > > > @@ -2484,6 +2484,11 @@ static int __clk_init(struct device *dev, struct clk *clk_user) > > > if (core->ops->init) > > > core->ops->init(core->hw); > > > > > > + if (core->flags & CLK_IS_CRITICAL) { > > > + clk_core_prepare(core); > > > + clk_core_enable(core); > > > + } > > > > What do we do if this is an orphan clk? From what I can tell > > we're not going to increment the ref count on the parents that > > may or may not appear at some later time when this flag is set. > > I don't see how this is any different than any other orphan clock. > __clk_set_parent_before and __clk_set_parent_after should still handle > migration and propagation of the {prepare,enable}_count when it is > finally re-parented. >From what I can see we don't call __clk_set_parent_before() or __clk_set_parent_after() when we're reparenting orphans to registered clks. We just call clk_core_reparent() that does mostly a list manipulation and recalc down the tree (BTW we probably shouldn't recalc at all if a clk is still orphaned because the rate is totally bogus). > > (as an aside, that code conditionally calls clk_prepare AND clk_enable > based solely on the prepare refcount, which seems weird to me...) Yeah I think I was questioning why we need to call clk_enable() there too so we should probably revisit this topic in another thread. > > > Furthermore, do we want to propagate the CLK_IS_CRITICAL flag up > > to all the parent clocks so that the warning mechanism spits out > > errors for parent clocks? I suppose that may not be very useful > > assuming refcounts are correct, but it may be useful to know > > which clocks are critical and which ones aren't during debug. > > No, propagating flags is a bad idea. Existing prepare/enable ref counts > should do the job for us. > > Regarding debug, propagating the flag will hurt debug-ability. We > already expose the clk_core->flags in sysfs, and debuggers can grep for > the CRITICAL flag there to find any spuriously enabled clocks. > Awesome. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
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