MIPS: mm: Define activate_mm() using switch_mm()

MIPS has separate definitions of activate_mm() & switch_mm() which are
identical apart from switch_mm() checking that the ASID is valid before
acquiring a new one.

We know that when activate_mm() is called cpu_context(X, mm) will be
zero, and this will never be considered a valid ASID because we never
allow the ASID version number to be zero, instead beginning with version
1 using asid_first_version(). Therefore switch_mm() will always allocate
a new ASID when called for a new task, meaning that it will behave
identically to activate_mm().

Take advantage of this to remove the duplication & define activate_mm()
using switch_mm() just like many other architectures do.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org

arch/mips/include/asm/mmu_context.h

@@ -166,35 +166,9 @@ static inline void destroy_context(struct mm_struct *mm)
 	dsemul_mm_cleanup(mm);
 }
 
+#define activate_mm(prev, next)	switch_mm(prev, next, current)
 #define deactivate_mm(tsk, mm)	do { } while (0)
 
-/*
- * After we have set current->mm to a new value, this activates
- * the context for the new mm so we see the new mappings.
- */
-static inline void
-activate_mm(struct mm_struct *prev, struct mm_struct *next)
-{
-	unsigned long flags;
-	unsigned int cpu = smp_processor_id();
-
-	local_irq_save(flags);
-
-	htw_stop();
-	/* Unconditionally get a new ASID.  */
-	get_new_mmu_context(next, cpu);
-
-	write_c0_entryhi(cpu_asid(cpu, next));
-	TLBMISS_HANDLER_SETUP_PGD(next->pgd);
-
-	/* mark mmu ownership change */
-	cpumask_clear_cpu(cpu, mm_cpumask(prev));
-	cpumask_set_cpu(cpu, mm_cpumask(next));
-	htw_start();
-
-	local_irq_restore(flags);
-}
-
 /*
  * If mm is currently active_mm, we can't really drop it.  Instead,
  * we will get a new one for it.