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/of_device.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/string.h>
  20 #include <linux/types.h>
  21
  22 #include "physmap-bt1-rom.h"
  23
  24 /*
  25  * Baikal-T1 SoC ROMs are only accessible by the dword-aligned instructions.
  26  * We have to take this into account when implementing the data read-methods.
  27  * Note there is no need in bothering with endianness, since both Baikal-T1
  28  * CPU and MMIO are LE.
  29  */
  30 static map_word __xipram bt1_rom_map_read(struct map_info *map,
  31                                           unsigned long ofs)
  32 {
  33         void __iomem *src = map->virt + ofs;
  34         unsigned int shift;
  35         map_word ret;
  36         u32 data;
  37
  38         /* Read data within offset dword. */
  39         shift = (uintptr_t)src & 0x3;
  40         data = readl_relaxed(src - shift);
  41         if (!shift) {
  42                 ret.x[0] = data;
  43                 return ret;
  44         }
  45         ret.x[0] = data >> (shift * BITS_PER_BYTE);
  46
  47         /* Read data from the next dword. */
  48         shift = 4 - shift;
  49         if (ofs + shift >= map->size)
  50                 return ret;
  51
  52         data = readl_relaxed(src + shift);
  53         ret.x[0] |= data << (shift * BITS_PER_BYTE);
  54
  55         return ret;
  56 }
  57
  58 static void __xipram bt1_rom_map_copy_from(struct map_info *map,
  59                                            void *to, unsigned long from,
  60                                            ssize_t len)
  61 {
  62         void __iomem *src = map->virt + from;
  63         unsigned int shift, chunk;
  64         u32 data;
  65
  66         if (len <= 0 || from >= map->size)
  67                 return;
  68
  69         /* Make sure we don't go over the map limit. */
  70         len = min_t(ssize_t, map->size - from, len);
  71
  72         /*
  73          * Since requested data size can be pretty big we have to implement
  74          * the copy procedure as optimal as possible. That's why it's split
  75          * up into the next three stages: unaligned head, aligned body,
  76          * unaligned tail.
  77          */
  78         shift = (uintptr_t)src & 0x3;
  79         if (shift) {
  80                 chunk = min_t(ssize_t, 4 - shift, len);
  81                 data = readl_relaxed(src - shift);
  82                 memcpy(to, &data + shift, chunk);
  83                 src += chunk;
  84                 to += chunk;
  85                 len -= chunk;
  86         }
  87
  88         while (len >= 4) {
  89                 data = readl_relaxed(src);
  90                 memcpy(to, &data, 4);
  91                 src += 4;
  92                 to += 4;
  93                 len -= 4;
  94         }
  95
  96         if (len) {
  97                 data = readl_relaxed(src);
  98                 memcpy(to, &data, len);
  99         }
 100 }
 101
 102 int of_flash_probe_bt1_rom(struct platform_device *pdev,
 103                            struct device_node *np,
 104                            struct map_info *map)
 105 {
 106         struct device *dev = &pdev->dev;
 107
 108         /* It's supposed to be read-only MTD. */
 109         if (!of_device_is_compatible(np, "mtd-rom")) {
 110                 dev_info(dev, "No mtd-rom compatible string\n");
 111                 return 0;
 112         }
 113
 114         /* Multiplatform guard. */
 115         if (!of_device_is_compatible(np, "baikal,bt1-int-rom"))
 116                 return 0;
 117
 118         /* Sanity check the device parameters retrieved from DTB. */
 119         if (map->bankwidth != 4)
 120                 dev_warn(dev, "Bank width is supposed to be 32 bits wide\n");
 121
 122         map->read = bt1_rom_map_read;
 123         map->copy_from = bt1_rom_map_copy_from;
 124
 125         return 0;
 126 }