drivers/mtd/maps/physmap-bt1-rom.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
   4  *
   5  * Authors:
   6  *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
   7  *
   8  * Baikal-T1 Physically Mapped Internal ROM driver
   9  */
  10 #include <linux/bits.h>
  11 #include <linux/device.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mtd/map.h>
  14 #include <linux/mtd/xip.h>
  15 #include <linux/mux/consumer.h>
  16 #include <linux/of.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/string.h>
  19 #include <linux/types.h>
  20
  21 #include "physmap-bt1-rom.h"
  22
  23 /*
  24  * Baikal-T1 SoC ROMs are only accessible by the dword-aligned instructions.
  25  * We have to take this into account when implementing the data read-methods.
  26  * Note there is no need in bothering with endianness, since both Baikal-T1
  27  * CPU and MMIO are LE.
  28  */
  29 static map_word __xipram bt1_rom_map_read(struct map_info *map,
  30                                           unsigned long ofs)
  31 {
  32         void __iomem *src = map->virt + ofs;
  33         unsigned int shift;
  34         map_word ret;
  35         u32 data;
  36
  37         /* Read data within offset dword. */
  38         shift = (uintptr_t)src & 0x3;
  39         data = readl_relaxed(src - shift);
  40         if (!shift) {
  41                 ret.x[0] = data;
  42                 return ret;
  43         }
  44         ret.x[0] = data >> (shift * BITS_PER_BYTE);
  45
  46         /* Read data from the next dword. */
  47         shift = 4 - shift;
  48         if (ofs + shift >= map->size)
  49                 return ret;
  50
  51         data = readl_relaxed(src + shift);
  52         ret.x[0] |= data << (shift * BITS_PER_BYTE);
  53
  54         return ret;
  55 }
  56
  57 static void __xipram bt1_rom_map_copy_from(struct map_info *map,
  58                                            void *to, unsigned long from,
  59                                            ssize_t len)
  60 {
  61         void __iomem *src = map->virt + from;
  62         unsigned int shift, chunk;
  63         u32 data;
  64
  65         if (len <= 0 || from >= map->size)
  66                 return;
  67
  68         /* Make sure we don't go over the map limit. */
  69         len = min_t(ssize_t, map->size - from, len);
  70
  71         /*
  72          * Since requested data size can be pretty big we have to implement
  73          * the copy procedure as optimal as possible. That's why it's split
  74          * up into the next three stages: unaligned head, aligned body,
  75          * unaligned tail.
  76          */
  77         shift = (uintptr_t)src & 0x3;
  78         if (shift) {
  79                 chunk = min_t(ssize_t, 4 - shift, len);
  80                 data = readl_relaxed(src - shift);
  81                 memcpy(to, (char *)&data + shift, chunk);
  82                 src += chunk;
  83                 to += chunk;
  84                 len -= chunk;
  85         }
  86
  87         while (len >= 4) {
  88                 data = readl_relaxed(src);
  89                 memcpy(to, &data, 4);
  90                 src += 4;
  91                 to += 4;
  92                 len -= 4;
  93         }
  94
  95         if (len) {
  96                 data = readl_relaxed(src);
  97                 memcpy(to, &data, len);
  98         }
  99 }
 100
 101 int of_flash_probe_bt1_rom(struct platform_device *pdev,
 102                            struct device_node *np,
 103                            struct map_info *map)
 104 {
 105         struct device *dev = &pdev->dev;
 106
 107         /* It's supposed to be read-only MTD. */
 108         if (!of_device_is_compatible(np, "mtd-rom")) {
 109                 dev_info(dev, "No mtd-rom compatible string\n");
 110                 return 0;
 111         }
 112
 113         /* Multiplatform guard. */
 114         if (!of_device_is_compatible(np, "baikal,bt1-int-rom"))
 115                 return 0;
 116
 117         /* Sanity check the device parameters retrieved from DTB. */
 118         if (map->bankwidth != 4)
 119                 dev_warn(dev, "Bank width is supposed to be 32 bits wide\n");
 120
 121         map->read = bt1_rom_map_read;
 122         map->copy_from = bt1_rom_map_copy_from;
 123
 124         return 0;
 125 }