ARM: fix cache-feroceon-l2 after stack based kmap_atomic()

Since commit 3e4d3af501 "mm: stack based kmap_atomic()", it is actively
wrong to rely on fixed kmap type indices (namely KM_L2_CACHE) as
kmap_atomic() totally ignores them and a concurrent instance of it may
happily reuse any slot for any purpose.  Because kmap_atomic() is now
able to deal with reentrancy, we can get rid of the ad hoc mapping here.

While the code is made much simpler, there is a needless cache flush
introduced by the usage of __kunmap_atomic().  It is not clear if the
performance difference to remove that is worth the cost in code
maintenance (I don't think there are that many highmem users on that
platform anyway) but that should be reconsidered when/if someone cares
enough to do some measurements.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>

arch/arm/mm/cache-feroceon-l2.c

@@ -13,13 +13,9 @@
  */
 
 #include <linux/init.h>
+#include <linux/highmem.h>
 #include <asm/cacheflush.h>
-#include <asm/kmap_types.h>
-#include <asm/fixmap.h>
-#include <asm/pgtable.h>
-#include <asm/tlbflush.h>
 #include <plat/cache-feroceon-l2.h>
-#include "mm.h"
 
 /*
  * Low-level cache maintenance operations.
@@ -39,27 +35,30 @@
  * between which we don't want to be preempted.
  */
 
-static inline unsigned long l2_start_va(unsigned long paddr)
+static inline unsigned long l2_get_va(unsigned long paddr)
 {
 #ifdef CONFIG_HIGHMEM
 	/*
-	 * Let's do our own fixmap stuff in a minimal way here.
 	 * Because range ops can't be done on physical addresses,
 	 * we simply install a virtual mapping for it only for the
 	 * TLB lookup to occur, hence no need to flush the untouched
-	 * memory mapping.  This is protected with the disabling of
-	 * interrupts by the caller.
+	 * memory mapping afterwards (note: a cache flush may happen
+	 * in some circumstances depending on the path taken in kunmap_atomic).
 	 */
-	unsigned long idx = KM_L2_CACHE + KM_TYPE_NR * smp_processor_id();
-	unsigned long vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	set_pte_ext(TOP_PTE(vaddr), pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL), 0);
-	local_flush_tlb_kernel_page(vaddr);
-	return vaddr + (paddr & ~PAGE_MASK);
+	void *vaddr = kmap_atomic_pfn(paddr >> PAGE_SHIFT);
+	return (unsigned long)vaddr + (paddr & ~PAGE_MASK);
 #else
 	return __phys_to_virt(paddr);
 #endif
 }
 
+static inline void l2_put_va(unsigned long vaddr)
+{
+#ifdef CONFIG_HIGHMEM
+	kunmap_atomic((void *)vaddr);
+#endif
+}
+
 static inline void l2_clean_pa(unsigned long addr)
 {
 	__asm__("mcr p15, 1, %0, c15, c9, 3" : : "r" (addr));
@@ -76,13 +75,14 @@ static inline void l2_clean_pa_range(unsigned long start, unsigned long end)
 	 */
 	BUG_ON((start ^ end) >> PAGE_SHIFT);
 
-	raw_local_irq_save(flags);
-	va_start = l2_start_va(start);
+	va_start = l2_get_va(start);
 	va_end = va_start + (end - start);
+	raw_local_irq_save(flags);
 	__asm__("mcr p15, 1, %0, c15, c9, 4\n\t"
 		"mcr p15, 1, %1, c15, c9, 5"
 		: : "r" (va_start), "r" (va_end));
 	raw_local_irq_restore(flags);
+	l2_put_va(va_start);
 }
 
 static inline void l2_clean_inv_pa(unsigned long addr)
@@ -106,13 +106,14 @@ static inline void l2_inv_pa_range(unsigned long start, unsigned long end)
 	 */
 	BUG_ON((start ^ end) >> PAGE_SHIFT);
 
-	raw_local_irq_save(flags);
-	va_start = l2_start_va(start);
+	va_start = l2_get_va(start);
 	va_end = va_start + (end - start);
+	raw_local_irq_save(flags);
 	__asm__("mcr p15, 1, %0, c15, c11, 4\n\t"
 		"mcr p15, 1, %1, c15, c11, 5"
 		: : "r" (va_start), "r" (va_end));
 	raw_local_irq_restore(flags);
+	l2_put_va(va_start);
 }
 
 static inline void l2_inv_all(void)