drivers/mtd/maps/physmap-ixp4xx.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Intel IXP4xx OF physmap add-on
   4  * Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
   5  *
   6  * Based on the ixp4xx.c map driver, originally written by:
   7  * Intel Corporation
   8  * Deepak Saxena <dsaxena@mvista.com>
   9  * Copyright (C) 2002 Intel Corporation
  10  * Copyright (C) 2003-2004 MontaVista Software, Inc.
  11  */
  12 #include <linux/export.h>
  13 #include <linux/of.h>
  14 #include <linux/of_device.h>
  15 #include <linux/mtd/map.h>
  16 #include <linux/mtd/xip.h>
  17 #include "physmap-ixp4xx.h"
  18
  19 /*
  20  * Read/write a 16 bit word from flash address 'addr'.
  21  *
  22  * When the cpu is in little-endian mode it swizzles the address lines
  23  * ('address coherency') so we need to undo the swizzling to ensure commands
  24  * and the like end up on the correct flash address.
  25  *
  26  * To further complicate matters, due to the way the expansion bus controller
  27  * handles 32 bit reads, the byte stream ABCD is stored on the flash as:
  28  *     D15    D0
  29  *     +---+---+
  30  *     | A | B | 0
  31  *     +---+---+
  32  *     | C | D | 2
  33  *     +---+---+
  34  * This means that on LE systems each 16 bit word must be swapped. Note that
  35  * this requires CONFIG_MTD_CFI_BE_BYTE_SWAP to be enabled to 'unswap' the CFI
  36  * data and other flash commands which are always in D7-D0.
  37  */
  38 #ifndef CONFIG_CPU_BIG_ENDIAN
  39
  40 static inline u16 flash_read16(void __iomem *addr)
  41 {
  42         return be16_to_cpu(__raw_readw((void __iomem *)((unsigned long)addr ^ 0x2)));
  43 }
  44
  45 static inline void flash_write16(u16 d, void __iomem *addr)
  46 {
  47         __raw_writew(cpu_to_be16(d), (void __iomem *)((unsigned long)addr ^ 0x2));
  48 }
  49
  50 #define BYTE0(h)        ((h) & 0xFF)
  51 #define BYTE1(h)        (((h) >> 8) & 0xFF)
  52
  53 #else
  54
  55 static inline u16 flash_read16(const void __iomem *addr)
  56 {
  57         return __raw_readw(addr);
  58 }
  59
  60 static inline void flash_write16(u16 d, void __iomem *addr)
  61 {
  62         __raw_writew(d, addr);
  63 }
  64
  65 #define BYTE0(h)        (((h) >> 8) & 0xFF)
  66 #define BYTE1(h)        ((h) & 0xFF)
  67 #endif
  68
  69 static map_word ixp4xx_read16(struct map_info *map, unsigned long ofs)
  70 {
  71         map_word val;
  72
  73         val.x[0] = flash_read16(map->virt + ofs);
  74         return val;
  75 }
  76
  77 /*
  78  * The IXP4xx expansion bus only allows 16-bit wide acceses
  79  * when attached to a 16-bit wide device (such as the 28F128J3A),
  80  * so we can't just memcpy_fromio().
  81  */
  82 static void ixp4xx_copy_from(struct map_info *map, void *to,
  83                              unsigned long from, ssize_t len)
  84 {
  85         u8 *dest = (u8 *) to;
  86         void __iomem *src = map->virt + from;
  87
  88         if (len <= 0)
  89                 return;
  90
  91         if (from & 1) {
  92                 *dest++ = BYTE1(flash_read16(src-1));
  93                 src++;
  94                 --len;
  95         }
  96
  97         while (len >= 2) {
  98                 u16 data = flash_read16(src);
  99                 *dest++ = BYTE0(data);
 100                 *dest++ = BYTE1(data);
 101                 src += 2;
 102                 len -= 2;
 103         }
 104
 105         if (len > 0)
 106                 *dest++ = BYTE0(flash_read16(src));
 107 }
 108
 109 static void ixp4xx_write16(struct map_info *map, map_word d, unsigned long adr)
 110 {
 111         flash_write16(d.x[0], map->virt + adr);
 112 }
 113
 114 int of_flash_probe_ixp4xx(struct platform_device *pdev,
 115                           struct device_node *np,
 116                           struct map_info *map)
 117 {
 118         struct device *dev = &pdev->dev;
 119
 120         /* Multiplatform guard */
 121         if (!of_device_is_compatible(np, "intel,ixp4xx-flash"))
 122                 return 0;
 123
 124         map->read = ixp4xx_read16;
 125         map->write = ixp4xx_write16;
 126         map->copy_from = ixp4xx_copy_from;
 127         map->copy_to = NULL;
 128
 129         dev_info(dev, "initialized Intel IXP4xx-specific physmap control\n");
 130
 131         return 0;
 132 }