arch/metag/mm/maccess.c

   1 /*
   2  * safe read and write memory routines callable while atomic
   3  *
   4  * Copyright 2012 Imagination Technologies
   5  */
   6
   7 #include <linux/uaccess.h>
   8 #include <asm/io.h>
   9
  10 /*
  11  * The generic probe_kernel_write() uses the user copy code which can split the
  12  * writes if the source is unaligned, and repeats writes to make exceptions
  13  * precise. We override it here to avoid these things happening to memory mapped
  14  * IO memory where they could have undesired effects.
  15  * Due to the use of CACHERD instruction this only works on Meta2 onwards.
  16  */
  17 #ifdef CONFIG_METAG_META21
  18 long probe_kernel_write(void *dst, const void *src, size_t size)
  19 {
  20         unsigned long ldst = (unsigned long)dst;
  21         void __iomem *iodst = (void __iomem *)dst;
  22         unsigned long lsrc = (unsigned long)src;
  23         const u8 *psrc = (u8 *)src;
  24         unsigned int pte, i;
  25         u8 bounce[8] __aligned(8);
  26
  27         if (!size)
  28                 return 0;
  29
  30         /* Use the write combine bit to decide is the destination is MMIO. */
  31         pte = __builtin_meta2_cacherd(dst);
  32
  33         /* Check the mapping is valid and writeable. */
  34         if ((pte & (MMCU_ENTRY_WR_BIT | MMCU_ENTRY_VAL_BIT))
  35             != (MMCU_ENTRY_WR_BIT | MMCU_ENTRY_VAL_BIT))
  36                 return -EFAULT;
  37
  38         /* Fall back to generic version for cases we're not interested in. */
  39         if (pte & MMCU_ENTRY_WRC_BIT    || /* write combined memory */
  40             (ldst & (size - 1))         || /* destination unaligned */
  41             size > 8                    || /* more than max write size */
  42             (size & (size - 1)))           /* non power of 2 size */
  43                 return __probe_kernel_write(dst, src, size);
  44
  45         /* If src is unaligned, copy to the aligned bounce buffer first. */
  46         if (lsrc & (size - 1)) {
  47                 for (i = 0; i < size; ++i)
  48                         bounce[i] = psrc[i];
  49                 psrc = bounce;
  50         }
  51
  52         switch (size) {
  53         case 1:
  54                 writeb(*psrc, iodst);
  55                 break;
  56         case 2:
  57                 writew(*(const u16 *)psrc, iodst);
  58                 break;
  59         case 4:
  60                 writel(*(const u32 *)psrc, iodst);
  61                 break;
  62         case 8:
  63                 writeq(*(const u64 *)psrc, iodst);
  64                 break;
  65         }
  66         return 0;
  67 }
  68 #endif