Re: [PATCH] arm: sched: stop sched_clock() during suspend
From: Linus Walleij
Date: Tue Oct 23 2012 - 06:11:13 EST
On Mon, Oct 22, 2012 at 1:54 PM, Felipe Balbi <balbi@xxxxxx> wrote:
> The scheduler imposes a requirement to sched_clock()
> which is to stop the clock during suspend, if we don't
> do that IRQ threads will be rescheduled in the future
> which might cause transfers to timeout depending on
> how driver is written.
> This became an issue on OMAP when we converted omap-i2c.c
> to use threaded IRQs, it turned out that depending on how
> much time we spent on suspend, the I2C IRQ thread would
> end up being rescheduled so far in the future that I2C
> transfers would timeout and, because omap_hsmmc depends
> on an I2C-connected device to detect if an MMC card is
> inserted in the slot, our rootfs would just vanish.
> arch/arm/kernel/sched_clock.c already had an optional
> implementation (sched_clock_needs_suspend()) which would
> handle scheduler's requirement properly, what this patch
> does is simply to make that implementation non-optional.
> This has been tested with beagleboard XM (OMAP3630) and
> pandaboard rev A3 (OMAP4430). Suspend to RAM is now working
> after this patch.
> Signed-off-by: Felipe Balbi <balbi@xxxxxx>
After Russell explains so I get it:
Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
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