ARM: get rid of kmap_high_l1_vipt()

Since commit 3e4d3af "mm: stack based kmap_atomic()", it is no longer
necessary to carry an ad hoc version of kmap_atomic() added in commit
7e5a69e "ARM: 6007/1: fix highmem with VIPT cache and DMA" to cope
with reentrancy.

In fact, it is now actively wrong to rely on fixed kmap type indices
(namely KM_L1_CACHE) as kmap_atomic() totally ignores them now and a
concurrent instance of it may reuse any slot for any purpose.

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

arch/arm/include/asm/highmem.h

@@ -25,9 +25,6 @@ extern void *kmap_high(struct page *page);
 extern void *kmap_high_get(struct page *page);
 extern void kunmap_high(struct page *page);
 
-extern void *kmap_high_l1_vipt(struct page *page, pte_t *saved_pte);
-extern void kunmap_high_l1_vipt(struct page *page, pte_t saved_pte);
-
 /*
  * The following functions are already defined by <linux/highmem.h>
  * when CONFIG_HIGHMEM is not set.

arch/arm/mm/dma-mapping.c

@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
+#include <linux/highmem.h>
 
 #include <asm/memory.h>
 #include <asm/highmem.h>
@@ -480,10 +481,10 @@ static void dma_cache_maint_page(struct page *page, unsigned long offset,
 				op(vaddr, len, dir);
 				kunmap_high(page);
 			} else if (cache_is_vipt()) {
-				pte_t saved_pte;
-				vaddr = kmap_high_l1_vipt(page, &saved_pte);
+				/* unmapped pages might still be cached */
+				vaddr = kmap_atomic(page);
 				op(vaddr + offset, len, dir);
-				kunmap_high_l1_vipt(page, saved_pte);
+				kunmap_atomic(vaddr);
 			}
 		} else {
 			vaddr = page_address(page) + offset;

arch/arm/mm/flush.c

@@ -10,6 +10,7 @@
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
+#include <linux/highmem.h>
 
 #include <asm/cacheflush.h>
 #include <asm/cachetype.h>
@@ -180,10 +181,10 @@ void __flush_dcache_page(struct address_space *mapping, struct page *page)
 			__cpuc_flush_dcache_area(addr, PAGE_SIZE);
 			kunmap_high(page);
 		} else if (cache_is_vipt()) {
-			pte_t saved_pte;
-			addr = kmap_high_l1_vipt(page, &saved_pte);
+			/* unmapped pages might still be cached */
+			addr = kmap_atomic(page);
 			__cpuc_flush_dcache_area(addr, PAGE_SIZE);
-			kunmap_high_l1_vipt(page, saved_pte);
+			kunmap_atomic(addr);
 		}
 	}
 

arch/arm/mm/highmem.c

@@ -140,90 +140,3 @@ struct page *kmap_atomic_to_page(const void *ptr)
 	pte = TOP_PTE(vaddr);
 	return pte_page(*pte);
 }
-
-#ifdef CONFIG_CPU_CACHE_VIPT
-
-#include <linux/percpu.h>
-
-/*
- * The VIVT cache of a highmem page is always flushed before the page
- * is unmapped. Hence unmapped highmem pages need no cache maintenance
- * in that case.
- *
- * However unmapped pages may still be cached with a VIPT cache, and
- * it is not possible to perform cache maintenance on them using physical
- * addresses unfortunately.  So we have no choice but to set up a temporary
- * virtual mapping for that purpose.
- *
- * Yet this VIPT cache maintenance may be triggered from DMA support
- * functions which are possibly called from interrupt context. As we don't
- * want to keep interrupt disabled all the time when such maintenance is
- * taking place, we therefore allow for some reentrancy by preserving and
- * restoring the previous fixmap entry before the interrupted context is
- * resumed.  If the reentrancy depth is 0 then there is no need to restore
- * the previous fixmap, and leaving the current one in place allow it to
- * be reused the next time without a TLB flush (common with DMA).
- */
-
-static DEFINE_PER_CPU(int, kmap_high_l1_vipt_depth);
-
-void *kmap_high_l1_vipt(struct page *page, pte_t *saved_pte)
-{
-	unsigned int idx, cpu;
-	int *depth;
-	unsigned long vaddr, flags;
-	pte_t pte, *ptep;
-
-	if (!in_interrupt())
-		preempt_disable();
-
-	cpu = smp_processor_id();
-	depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
-
-	idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	ptep = TOP_PTE(vaddr);
-	pte = mk_pte(page, kmap_prot);
-
-	raw_local_irq_save(flags);
-	(*depth)++;
-	if (pte_val(*ptep) == pte_val(pte)) {
-		*saved_pte = pte;
-	} else {
-		*saved_pte = *ptep;
-		set_pte_ext(ptep, pte, 0);
-		local_flush_tlb_kernel_page(vaddr);
-	}
-	raw_local_irq_restore(flags);
-
-	return (void *)vaddr;
-}
-
-void kunmap_high_l1_vipt(struct page *page, pte_t saved_pte)
-{
-	unsigned int idx, cpu = smp_processor_id();
-	int *depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
-	unsigned long vaddr, flags;
-	pte_t pte, *ptep;
-
-	idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	ptep = TOP_PTE(vaddr);
-	pte = mk_pte(page, kmap_prot);
-
-	BUG_ON(pte_val(*ptep) != pte_val(pte));
-	BUG_ON(*depth <= 0);
-
-	raw_local_irq_save(flags);
-	(*depth)--;
-	if (*depth != 0 && pte_val(pte) != pte_val(saved_pte)) {
-		set_pte_ext(ptep, saved_pte, 0);
-		local_flush_tlb_kernel_page(vaddr);
-	}
-	raw_local_irq_restore(flags);
-
-	if (!in_interrupt())
-		preempt_enable();
-}
-
-#endif  /* CONFIG_CPU_CACHE_VIPT */