Hi,
On Mon, Oct 22, 2012 at 02:54:37PM +0300, Felipe Balbi 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>
just adding more guys to Cc. Please add more if I have missed someone.
> ---
> arch/arm/include/asm/sched_clock.h | 2 --
> arch/arm/kernel/sched_clock.c | 18 ++++--------------
> 2 files changed, 4 insertions(+), 16 deletions(-)
>
> diff --git a/arch/arm/include/asm/sched_clock.h b/arch/arm/include/asm/sched_clock.h
> index 05b8e82..e3f7572 100644
> --- a/arch/arm/include/asm/sched_clock.h
> +++ b/arch/arm/include/asm/sched_clock.h
> @@ -10,7 +10,5 @@
>
> extern void sched_clock_postinit(void);
> extern void setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate);
> -extern void setup_sched_clock_needs_suspend(u32 (*read)(void), int bits,
> - unsigned long rate);
>
> #endif
> diff --git a/arch/arm/kernel/sched_clock.c b/arch/arm/kernel/sched_clock.c
> index e21bac2..fc6692e 100644
> --- a/arch/arm/kernel/sched_clock.c
> +++ b/arch/arm/kernel/sched_clock.c
> @@ -107,13 +107,6 @@ static void sched_clock_poll(unsigned long wrap_ticks)
> update_sched_clock();
> }
>
> -void __init setup_sched_clock_needs_suspend(u32 (*read)(void), int bits,
> - unsigned long rate)
> -{
> - setup_sched_clock(read, bits, rate);
> - cd.needs_suspend = true;
> -}
> -
> void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate)
> {
> unsigned long r, w;
> @@ -189,18 +182,15 @@ void __init sched_clock_postinit(void)
> static int sched_clock_suspend(void)
> {
> sched_clock_poll(sched_clock_timer.data);
> - if (cd.needs_suspend)
> - cd.suspended = true;
> + cd.suspended = true;
> return 0;
> }
>
> static void sched_clock_resume(void)
> {
> - if (cd.needs_suspend) {
> - cd.epoch_cyc = read_sched_clock();
> - cd.epoch_cyc_copy = cd.epoch_cyc;
> - cd.suspended = false;
> - }
> + cd.epoch_cyc = read_sched_clock();
> + cd.epoch_cyc_copy = cd.epoch_cyc;
> + cd.suspended = false;
> }
>
> static struct syscore_ops sched_clock_ops = {
> --
> 1.8.0.rc0
>
--
balbi
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