ARM: EXYNOS: add Exynos Dual Cluster Support

Quoted 7 lines · Dave Martin

Review

Quoted 4 lines · Vyacheslav Tyrtov

(quoted diff) +4 -0

+static int exynos_power_up(unsigned int cpu, unsigned int cluster)
+{
+     int ret;
+     local_irq_disable();

Should there be a local_fiq_disable() here also?

No. In fact this is paired with

Quoted 1 line

Quoted 1 line

+ arch_spin_lock(&exynos_lock);

to create the equivalent of a arch_spin_lock_irq(). And the reason is:

/*
* We can't use regular spinlocks. In the switcher case, it is possible
* for an outbound CPU to call power_down() after its inbound counterpart
* is already live using the same logical CPU number which trips lockdep
* debugging.
*/

Otherwise we simply would have used spin_lock_irq().

No FIQs are supposed to ever race with this code.

Quoted 1 line · Nicolas Pitre

No FIQs are supposed to ever race with this code.

There is an anomaly though: FIQ and external abort don't seem to get explicitly masked anywhere, either on the suspend or powerdown paths. Sometimes either or both remains unmasked (I tried some trace in the TC2 MCPM backend to confirm this.)

Looks like a possible omission in the arch/arm/ suspend and shutdown code, rather than a problem specific to MCPM.