From: Thomas Gleixner <tglx@linutronix.de>
To: Dong Aisheng <dongas86@gmail.com>
Cc: Shawn Guo <shawnguo@kernel.org>,
Lucas Stach <l.stach@pengutronix.de>,
Michael Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@codeaurora.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Stefan Agner <stefan@agner.ch>,
mingo@redhat.com, "kernel@pengutronix.de" <kernel@pengutronix.de>,
linux-clk@vger.kernel.org,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled
Date: Mon, 6 Jun 2016 15:20:03 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.11.1606061448010.28031@nanos> (raw)
In-Reply-To: <20160602145915.GA31124@shlinux2>
On Thu, 2 Jun 2016, Dong Aisheng wrote:
> On Wed, Apr 27, 2016 at 12:15:00PM +0200, Thomas Gleixner wrote:
> > Calling a function which might sleep _BEFORE_ kernel_init() is wrong. Don't
> > try to work around such an issue by doing magic irq_disabled() checks and busy
> > loops. Fix the call site and be done with it.
> >
>
> IRQ chip and clocksource are also initialised before kernel_init()
> which may call clk APIs like clk_prepare_enable().
> We may not be able to guarantee those clocks are unsleepable.
>
> e.g.
> For IRQ chip, the arm,gic documents the optional clocks property in
> Documentation/devicetree/bindings/interrupt-controller/arm,gic.txt.
> Although there seems no user currently, not sure there might be
> a exception in the future.
>
> For clocksource driver, it's quite common to call clk APIs to
> enable and get clock rate which may also cause sleep.
> e.g. ARM twd clock in arch/arm/kernel/smp_twd.c.
>
> If we have to avoid the possible sleep caused by these clocks,
> we may need to manually check it and change the related clocks
> (e.g PLLs) from sleepable to busy loops.
> But that is not a good solution and may also not stable when
> clock varies.
>
> It looks like not easy to find a generic solution for them.
> What's your suggestion?
I think we should split the prepare callbacks up and move the handling logic
into the core.
clk_ops.prepare() Legacy callback
clk_ops.prepare_hw() Callback which writes to the hardware
clk_ops.prepare_done() Callback which checks whether the prepare is completed
So now the core can do:
clk_prepare()
{
/* Legacy code should go away */
if (ops->prepare) {
ops->prepare();
return;
}
if (ops->prepare_hw)
ops->prepare_hw();
if (!ops->prepare_done())
return;
if (early_boot_or_suspend_resume()) {
/*
* Busy loop when we can't schedule in early boot,
* suspend and resume.
*/
while (!ops->prepare_done())
;
} else {
while (!ops->prepare_done())
usleep(clk->prepare_delay);
}
}
As a side effect that allows us to remove the gazillion of
while (!hw_ready)
usleep();
copies all over the place and we have a single point of control where we allow
the clocks to busy loop.
Toughts?
Thanks,
tglx
next prev parent reply other threads:[~2016-06-06 13:22 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-29 22:49 [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Stefan Agner
2016-01-29 22:49 ` [PATCH 2/2] clk: imx: return correct frequency for Ethernet PLL Stefan Agner
2016-01-29 23:35 ` [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Joshua Clayton
2016-01-30 1:16 ` Stephen Boyd
2016-04-26 17:04 ` Stefan Agner
2016-04-16 1:00 ` Stephen Boyd
2016-04-18 1:58 ` Shawn Guo
2016-04-21 3:45 ` Dong Aisheng
2016-04-26 1:23 ` Shawn Guo
2016-04-26 5:51 ` Dong Aisheng
2016-04-26 9:24 ` Shawn Guo
2016-04-26 9:31 ` Lucas Stach
2016-04-26 11:16 ` Dong Aisheng
2016-04-26 11:27 ` Dong Aisheng
2016-04-27 1:58 ` Shawn Guo
2016-04-27 2:45 ` Dong Aisheng
2016-04-27 2:56 ` Fabio Estevam
2016-04-27 7:28 ` Stefan Agner
2016-04-27 8:53 ` Dong Aisheng
2016-04-27 2:57 ` Dong Aisheng
2016-04-27 7:24 ` Shawn Guo
2016-04-27 7:26 ` Stefan Agner
2016-04-27 8:48 ` Dong Aisheng
2016-04-27 7:34 ` Stefan Agner
2016-04-27 8:57 ` Dong Aisheng
2016-04-27 10:15 ` Thomas Gleixner
2016-04-29 9:45 ` [RFC PATCH 1/1] clk: imx7d: move clk setting out of imx7d_clocks_init Dong Aisheng
2016-04-29 9:55 ` Dong Aisheng
2016-04-29 12:31 ` Lucas Stach
2016-04-30 2:04 ` Stefan Agner
2016-06-02 15:19 ` Dong Aisheng
2016-05-25 21:54 ` [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled Stefan Agner
2016-06-02 14:59 ` Dong Aisheng
2016-06-06 13:20 ` Thomas Gleixner [this message]
2016-06-07 7:04 ` Dong Aisheng
2016-06-09 20:08 ` Thomas Gleixner
2016-06-09 22:14 ` Stefan Agner
2016-06-09 22:55 ` Thomas Gleixner
2016-06-12 12:24 ` Dong Aisheng
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