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