csky: Use generic asid algorithm to implement switch_mm

Use linux generic asid/vmid algorithm to implement csky
switch_mm function. The algorithm is from arm and it could
work with SMP system. It'll help reduce tlb flush for
switch_mm in task/vm switch.

Signed-off-by: Guo Ren <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>

arch/csky/abiv1/inc/abi/ckmmu.h

···
 	cpwcr("cpcr8", 0x04000000);
 }
 
+
+static inline void local_tlb_invalid_all(void)
+{
+	tlb_invalid_all();
+}
+
 static inline void tlb_invalid_indexed(void)
 {
 	cpwcr("cpcr8", 0x02000000);

arch/csky/abiv2/inc/abi/ckmmu.h

···
 #endif
 }
 
+static inline void local_tlb_invalid_all(void)
+{
+#ifdef CONFIG_CPU_HAS_TLBI
+	asm volatile("tlbi.all\n":::"memory");
+	sync_is();
+#else
+	tlb_invalid_all();
+#endif
+}
+
 static inline void tlb_invalid_indexed(void)
 {
 	mtcr("cr<8, 15>", 0x02000000);

arch/csky/include/asm/mmu.h

···
 #define __ASM_CSKY_MMU_H
 
 typedef struct {
+	atomic64_t	asid;
 	void *vdso;
 } mm_context_t;
 

arch/csky/include/asm/mmu_context.h

···
 #define TLBMISS_HANDLER_SETUP_PGD_KERNEL(pgd) \
 	setup_pgd(__pa(pgd), true)
 
-#define init_new_context(tsk,mm)	0
+#define ASID_MASK		((1 << CONFIG_CPU_ASID_BITS) - 1)
+#define cpu_asid(mm)		(atomic64_read(&mm->context.asid) & ASID_MASK)
+
+#define init_new_context(tsk,mm)	({ atomic64_set(&(mm)->context.asid, 0); 0; })
 #define activate_mm(prev,next)		switch_mm(prev, next, current)
 
 #define destroy_context(mm)		do {} while (0)
 #define enter_lazy_tlb(mm, tsk)		do {} while (0)
 #define deactivate_mm(tsk, mm)		do {} while (0)
 
+void check_and_switch_context(struct mm_struct *mm, unsigned int cpu);
+
 static inline void
 switch_mm(struct mm_struct *prev, struct mm_struct *next,
 	  struct task_struct *tsk)
 {
+	unsigned int cpu = smp_processor_id();
+
 	if (prev != next)
-		tlb_invalid_all();
+		check_and_switch_context(next, cpu);
 
 	TLBMISS_HANDLER_SETUP_PGD(next->pgd);
+	write_mmu_entryhi(next->context.asid.counter);
 }
 #endif /* __ASM_CSKY_MMU_CONTEXT_H */

arch/csky/mm/Makefile

···
 obj-y +=			syscache.o
 obj-y +=			tlb.o
 obj-y +=			asid.o
+obj-y +=			context.o

arch/csky/mm/context.c

···
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#include <linux/bitops.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+
+#include <asm/asid.h>
+#include <asm/mmu_context.h>
+#include <asm/smp.h>
+#include <asm/tlbflush.h>
+
+static DEFINE_PER_CPU(atomic64_t, active_asids);
+static DEFINE_PER_CPU(u64, reserved_asids);
+
+struct asid_info asid_info;
+
+void check_and_switch_context(struct mm_struct *mm, unsigned int cpu)
+{
+	asid_check_context(&asid_info, &mm->context.asid, cpu, mm);
+}
+
+static void asid_flush_cpu_ctxt(void)
+{
+	local_tlb_invalid_all();
+}
+
+static int asids_init(void)
+{
+	BUG_ON(((1 << CONFIG_CPU_ASID_BITS) - 1) <= num_possible_cpus());
+
+	if (asid_allocator_init(&asid_info, CONFIG_CPU_ASID_BITS, 1,
+				asid_flush_cpu_ctxt))
+		panic("Unable to initialize ASID allocator for %lu ASIDs\n",
+		      NUM_ASIDS(&asid_info));
+
+	asid_info.active = &active_asids;
+	asid_info.reserved = &reserved_asids;
+
+	pr_info("ASID allocator initialised with %lu entries\n",
+		NUM_CTXT_ASIDS(&asid_info));
+
+	return 0;
+}
+early_initcall(asids_init);