openrisc: sleep instead of spin on secondary wait

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Currently we do a spin on secondary cpus when waiting to boot.  This
theoretically causes issues with power consumption and does cause issues
with qemu cycle burning (it starves cpu 0 from actually being able to
boot.)

This change puts each secondary cpu to sleep if they have a power
management unit, then signals them to wake via IPI when its time to boot.
If the cpus have no power management unit they will loop as before.

Note: The wakeup IPI requires a special interrupt handler as on secondary
cpu's the interrupt infrastructure is not yet established.  This
interrupt handler is set and reset by updating SPR_EVBAR.

Signed-off-by: Stafford Horne <shorne@gmail.com>

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This commit is contained in:

Stafford Horne 2017-06-24 07:09:59 +09:00

parent b441aab7aa

commit c056718464

2 changed files with 54 additions and 2 deletions

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51

arch/openrisc/kernel/head.S

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5

arch/openrisc/kernel/smp.c

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