nds32/mm/highmem: Switch to generic kmap atomic

The mapping code is odd and looks broken. See FIXME in the comment.

Also fix the harmless off by one in the FIX_KMAP_END define.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20201103095857.980576055@linutronix.de

arch/nds32/Kconfig.cpu

@@ -157,6 +157,7 @@ config HW_SUPPORT_UNALIGNMENT_ACCESS
 config HIGHMEM
 	bool "High Memory Support"
 	depends on MMU && !CPU_CACHE_ALIASING
+	select KMAP_LOCAL
 	help
 	  The address space of Andes processors is only 4 Gigabytes large
 	  and it has to accommodate user address space, kernel address

arch/nds32/include/asm/fixmap.h

@@ -6,7 +6,7 @@
 
 #ifdef CONFIG_HIGHMEM
 #include <linux/threads.h>
-#include <asm/kmap_types.h>
+#include <asm/kmap_size.h>
 #endif
 
 enum fixed_addresses {
@@ -14,7 +14,7 @@ enum fixed_addresses {
 	FIX_KMAP_RESERVED,
 	FIX_KMAP_BEGIN,
 #ifdef CONFIG_HIGHMEM
-	FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS),
+	FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_MAX_IDX * NR_CPUS) - 1,
 #endif
 	FIX_EARLYCON_MEM_BASE,
 	__end_of_fixed_addresses

arch/nds32/include/asm/highmem.h

@@ -5,7 +5,6 @@
 #define _ASM_HIGHMEM_H
 
 #include <asm/proc-fns.h>
-#include <asm/kmap_types.h>
 #include <asm/fixmap.h>
 
 /*
@@ -45,11 +44,22 @@ extern pte_t *pkmap_page_table;
 extern void kmap_init(void);
 
 /*
- * The following functions are already defined by <linux/highmem.h>
- * when CONFIG_HIGHMEM is not set.
+ * FIXME: The below looks broken vs. a kmap_atomic() in task context which
+ * is interupted and another kmap_atomic() happens in interrupt context.
+ * But what do I know about nds32. -- tglx
  */
-#ifdef CONFIG_HIGHMEM
-extern void *kmap_atomic_pfn(unsigned long pfn);
-#endif
+#define arch_kmap_local_post_map(vaddr, pteval)			\
+	do {							\
+		__nds32__tlbop_inv(vaddr);			\
+		__nds32__mtsr_dsb(vaddr, NDS32_SR_TLB_VPN);	\
+		__nds32__tlbop_rwr(pteval);			\
+		__nds32__isb();					\
+	} while (0)
+
+#define arch_kmap_local_pre_unmap(vaddr)			\
+	do {							\
+		__nds32__tlbop_inv(vaddr);			\
+		__nds32__isb();					\
+	} while (0)
 
 #endif

arch/nds32/mm/Makefile

@@ -3,7 +3,6 @@ obj-y				:= extable.o tlb.o fault.o init.o mmap.o \
                                    mm-nds32.o cacheflush.o proc.o
 
 obj-$(CONFIG_ALIGNMENT_TRAP)	+= alignment.o
-obj-$(CONFIG_HIGHMEM)           += highmem.o
 
 ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_proc.o     = $(CC_FLAGS_FTRACE)

arch/nds32/mm/highmem.c

-// SPDX-License-Identifier: GPL-2.0
-// Copyright (C) 2005-2017 Andes Technology Corporation
-
-#include <linux/export.h>
-#include <linux/highmem.h>
-#include <linux/sched.h>
-#include <linux/smp.h>
-#include <linux/interrupt.h>
-#include <linux/memblock.h>
-#include <asm/fixmap.h>
-#include <asm/tlbflush.h>
-
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
-	unsigned int idx;
-	unsigned long vaddr, pte;
-	int type;
-	pte_t *ptep;
-
-	type = kmap_atomic_idx_push();
-
-	idx = type + KM_TYPE_NR * smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	pte = (page_to_pfn(page) << PAGE_SHIFT) | prot;
-	ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
-	set_pte(ptep, pte);
-
-	__nds32__tlbop_inv(vaddr);
-	__nds32__mtsr_dsb(vaddr, NDS32_SR_TLB_VPN);
-	__nds32__tlbop_rwr(pte);
-	__nds32__isb();
-	return (void *)vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kvaddr)
-{
-	if (kvaddr >= (void *)FIXADDR_START) {
-		unsigned long vaddr = (unsigned long)kvaddr;
-		pte_t *ptep;
-		kmap_atomic_idx_pop();
-		__nds32__tlbop_inv(vaddr);
-		__nds32__isb();
-		ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
-		set_pte(ptep, 0);
-	}
-}
-EXPORT_SYMBOL(kunmap_atomic_high);