riscv: Add qspinlock support

In order to produce a generic kernel, a user can select
CONFIG_COMBO_SPINLOCKS which will fallback at runtime to the ticket
spinlock implementation if Zabha or Ziccrse a

riscv: Add qspinlock support

In order to produce a generic kernel, a user can select
CONFIG_COMBO_SPINLOCKS which will fallback at runtime to the ticket
spinlock implementation if Zabha or Ziccrse are not present.

Note that we can't use alternatives here because the discovery of
extensions is done too late and we need to start with the qspinlock
implementation because the ticket spinlock implementation would pollute
the spinlock value, so let's use static keys.

This is largely based on Guo's work and Leonardo reviews at [1].

Link: https://lore.kernel.org/linux-riscv/[email protected]/ [1]
Signed-off-by: Guo Ren <[email protected]>
Signed-off-by: Alexandre Ghiti <[email protected]>
Reviewed-by: Andrea Parri <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

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asm-generic: ticket-lock: Add separate ticket-lock.h

Add a separate ticket-lock.h to include multiple spinlock versions and
select one at compile time or runtime.

Reviewed-by: Leonardo Bras <leobra

asm-generic: ticket-lock: Add separate ticket-lock.h

Add a separate ticket-lock.h to include multiple spinlock versions and
select one at compile time or runtime.

Reviewed-by: Leonardo Bras <[email protected]>
Suggested-by: Arnd Bergmann <[email protected]>
Link: https://lore.kernel.org/linux-riscv/CAK8P3a2rnz9mQqhN6-e0CGUUv9rntRELFdxt_weiD7FxH7fkfQ@mail.gmail.com/
Signed-off-by: Guo Ren <[email protected]>
Signed-off-by: Guo Ren <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Andrew Jones <[email protected]>
Reviewed-by: Andrea Parri <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

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