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-rw-r--r--arch/metag/mm/maccess.c68
1 files changed, 68 insertions, 0 deletions
diff --git a/arch/metag/mm/maccess.c b/arch/metag/mm/maccess.c
new file mode 100644
index 000000000000..eba2cfc935b1
--- /dev/null
+++ b/arch/metag/mm/maccess.c
@@ -0,0 +1,68 @@
+/*
+ * safe read and write memory routines callable while atomic
+ *
+ * Copyright 2012 Imagination Technologies
+ */
+
+#include <linux/uaccess.h>
+#include <asm/io.h>
+
+/*
+ * The generic probe_kernel_write() uses the user copy code which can split the
+ * writes if the source is unaligned, and repeats writes to make exceptions
+ * precise. We override it here to avoid these things happening to memory mapped
+ * IO memory where they could have undesired effects.
+ * Due to the use of CACHERD instruction this only works on Meta2 onwards.
+ */
+#ifdef CONFIG_METAG_META21
+long probe_kernel_write(void *dst, const void *src, size_t size)
+{
+ unsigned long ldst = (unsigned long)dst;
+ void __iomem *iodst = (void __iomem *)dst;
+ unsigned long lsrc = (unsigned long)src;
+ const u8 *psrc = (u8 *)src;
+ unsigned int pte, i;
+ u8 bounce[8] __aligned(8);
+
+ if (!size)
+ return 0;
+
+ /* Use the write combine bit to decide is the destination is MMIO. */
+ pte = __builtin_meta2_cacherd(dst);
+
+ /* Check the mapping is valid and writeable. */
+ if ((pte & (MMCU_ENTRY_WR_BIT | MMCU_ENTRY_VAL_BIT))
+ != (MMCU_ENTRY_WR_BIT | MMCU_ENTRY_VAL_BIT))
+ return -EFAULT;
+
+ /* Fall back to generic version for cases we're not interested in. */
+ if (pte & MMCU_ENTRY_WRC_BIT || /* write combined memory */
+ (ldst & (size - 1)) || /* destination unaligned */
+ size > 8 || /* more than max write size */
+ (size & (size - 1))) /* non power of 2 size */
+ return __probe_kernel_write(dst, src, size);
+
+ /* If src is unaligned, copy to the aligned bounce buffer first. */
+ if (lsrc & (size - 1)) {
+ for (i = 0; i < size; ++i)
+ bounce[i] = psrc[i];
+ psrc = bounce;
+ }
+
+ switch (size) {
+ case 1:
+ writeb(*psrc, iodst);
+ break;
+ case 2:
+ writew(*(const u16 *)psrc, iodst);
+ break;
+ case 4:
+ writel(*(const u32 *)psrc, iodst);
+ break;
+ case 8:
+ writeq(*(const u64 *)psrc, iodst);
+ break;
+ }
+ return 0;
+}
+#endif