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SubjectRe: [PATCH v4 1/3] ARM: rockchip: fix the CPU soft reset
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Hi Caesar, Doug,

Am Sonntag, 7. Juni 2015, 13:51:24 schrieb Caesar Wang:
> 在 2015年06月07日 11:43, Doug Anderson 写道:
> > Caesar,
> >
> > On Sat, Jun 6, 2015 at 7:51 PM, Caesar Wang <wxt@rock-chips.com> wrote:
> >> @@ -150,13 +159,15 @@ static int __cpuinit
> >> rockchip_boot_secondary(unsigned
> >> int cpu,
> >>
> >> * sram_base_addr + 4: 0xdeadbeaf
> >> * sram_base_addr + 8: start address for pc
> >> * */
> >>
> >> - udelay(10);
> >> + udelay(20);
> >>
> >> I increased the 'udelay(20)' or 'udelay(50)' in
> >> rockchip_boot_secondary().
> >> Set#2 also can repro this issue over 22600 cycles with testing scripts.
> >> (about 1 hours)
> >>
> >> log:
> >> ================= 226 ============
> >> [ 4069.134419] CPU1: shutdown
> >> [ 4069.164431] CPU2: shutdown
> >> [ 4069.204475] CPU3: shutdown
> >> ......
> >> [ 4072.454453] CPU1: shutdown
> >> [ 4072.504436] CPU2: shutdown
> >> [ 4072.554426] CPU3: shutdown
> >> [ 4072.577827] CPU1: Booted secondary processor
> >> [ 4072.582611] CPU2: Booted secondary processor
> >> [ 4072.587426] CPU3: Booted secondary processor
> >> <hang>
> >>
> >> The set #4 will be better work.
> >
> > OK, I'm OK with this, but I'd like to get Heiko's opinion.
> >
> > Also:
> > * Just for kicks, does mdelay(1) work? I know that's 100x more than
>
> OK, it should delay more time.
>
> the mdelay(1) can be work over 50000 cycles, so that should be work.
>
>
> Perhaps, can we use 'usleep_range(500, 1000)' to work.
> Heiko, do you agree with it?

yep :-)

As I said before, doing

powerup, deassert_reset, wait_for_powerdomain

feels like it is only moving the problem a bit but is actually only working by
chance, as my [little bit of :-) ] common sense tells me, that we really only
should deassert the reset when we're sure that the core has power, i.e.

powerup, wait_for_powerdomain, deassert_reset

Also, when going down this path, please take a look at the slightly different
variant I posted as response to v3, as it makes the diff a bit smaller :-)


As for {u/m}delay vs. your usleep_ranges, I don't know if you're allowed to
sleep in this area. Other architectures only seem to use udelay in __cpu_up
which calls the smp_secondary_startup callback, like:

- arch/sh/kernel/smp.c
- arch/m32r/kernel/smpboot.c [is even a udelay(1000)
and more


Heiko

> > udelay(10), but previously we were actually looping waiting for the
> > power domain, right? ...so maybe the old code used to introduce a
> > pretty big delay.
> >
> > * Does anyone from the chip design team have any idea why patch set #4
> > works but patch set #2 doesn't? I know it's Sunday morning in China
> > right now, but maybe you could ask Monday?
> >
> >
> > Thanks!
> >
> > -Doug



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