arch/metag/mm/maccess.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * safe read and write memory routines callable while atomic
   4  *
   5  * Copyright 2012 Imagination Technologies
   6  */
   7
   8 #include <linux/uaccess.h>
   9 #include <asm/io.h>
  10
  11 /*
  12  * The generic probe_kernel_write() uses the user copy code which can split the
  13  * writes if the source is unaligned, and repeats writes to make exceptions
  14  * precise. We override it here to avoid these things happening to memory mapped
  15  * IO memory where they could have undesired effects.
  16  * Due to the use of CACHERD instruction this only works on Meta2 onwards.
  17  */
  18 #ifdef CONFIG_METAG_META21
  19 long probe_kernel_write(void *dst, const void *src, size_t size)
  20 {
  21         unsigned long ldst = (unsigned long)dst;
  22         void __iomem *iodst = (void __iomem *)dst;
  23         unsigned long lsrc = (unsigned long)src;
  24         const u8 *psrc = (u8 *)src;
  25         unsigned int pte, i;
  26         u8 bounce[8] __aligned(8);
  27
  28         if (!size)
  29                 return 0;
  30
  31         /* Use the write combine bit to decide is the destination is MMIO. */
  32         pte = __builtin_meta2_cacherd(dst);
  33
  34         /* Check the mapping is valid and writeable. */
  35         if ((pte & (MMCU_ENTRY_WR_BIT | MMCU_ENTRY_VAL_BIT))
  36             != (MMCU_ENTRY_WR_BIT | MMCU_ENTRY_VAL_BIT))
  37                 return -EFAULT;
  38
  39         /* Fall back to generic version for cases we're not interested in. */
  40         if (pte & MMCU_ENTRY_WRC_BIT    || /* write combined memory */
  41             (ldst & (size - 1))         || /* destination unaligned */
  42             size > 8                    || /* more than max write size */
  43             (size & (size - 1)))           /* non power of 2 size */
  44                 return __probe_kernel_write(dst, src, size);
  45
  46         /* If src is unaligned, copy to the aligned bounce buffer first. */
  47         if (lsrc & (size - 1)) {
  48                 for (i = 0; i < size; ++i)
  49                         bounce[i] = psrc[i];
  50                 psrc = bounce;
  51         }
  52
  53         switch (size) {
  54         case 1:
  55                 writeb(*psrc, iodst);
  56                 break;
  57         case 2:
  58                 writew(*(const u16 *)psrc, iodst);
  59                 break;
  60         case 4:
  61                 writel(*(const u32 *)psrc, iodst);
  62                 break;
  63         case 8:
  64                 writeq(*(const u64 *)psrc, iodst);
  65                 break;
  66         }
  67         return 0;
  68 }
  69 #endif