drivers/mtd/devices/mchp23k256.c

   1 /*
   2  * mchp23k256.c
   3  *
   4  * Driver for Microchip 23k256 SPI RAM chips
   5  *
   6  * Copyright © 2016 Andrew Lunn <andrew@lunn.ch>
   7  *
   8  * This code is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  */
  13 #include <linux/device.h>
  14 #include <linux/module.h>
  15 #include <linux/mtd/mtd.h>
  16 #include <linux/mtd/partitions.h>
  17 #include <linux/mutex.h>
  18 #include <linux/sched.h>
  19 #include <linux/sizes.h>
  20 #include <linux/spi/flash.h>
  21 #include <linux/spi/spi.h>
  22 #include <linux/of_device.h>
  23
  24 #define MAX_CMD_SIZE            4
  25
  26 struct mchp23_caps {
  27         u8 addr_width;
  28         unsigned int size;
  29 };
  30
  31 struct mchp23k256_flash {
  32         struct spi_device       *spi;
  33         struct mutex            lock;
  34         struct mtd_info         mtd;
  35         const struct mchp23_caps        *caps;
  36 };
  37
  38 #define MCHP23K256_CMD_WRITE_STATUS     0x01
  39 #define MCHP23K256_CMD_WRITE            0x02
  40 #define MCHP23K256_CMD_READ             0x03
  41 #define MCHP23K256_MODE_SEQ             BIT(6)
  42
  43 #define to_mchp23k256_flash(x) container_of(x, struct mchp23k256_flash, mtd)
  44
  45 static void mchp23k256_addr2cmd(struct mchp23k256_flash *flash,
  46                                 unsigned int addr, u8 *cmd)
  47 {
  48         int i;
  49
  50         /*
  51          * Address is sent in big endian (MSB first) and we skip
  52          * the first entry of the cmd array which contains the cmd
  53          * opcode.
  54          */
  55         for (i = flash->caps->addr_width; i > 0; i--, addr >>= 8)
  56                 cmd[i] = addr;
  57 }
  58
  59 static int mchp23k256_cmdsz(struct mchp23k256_flash *flash)
  60 {
  61         return 1 + flash->caps->addr_width;
  62 }
  63
  64 static int mchp23k256_write(struct mtd_info *mtd, loff_t to, size_t len,
  65                             size_t *retlen, const unsigned char *buf)
  66 {
  67         struct mchp23k256_flash *flash = to_mchp23k256_flash(mtd);
  68         struct spi_transfer transfer[2] = {};
  69         struct spi_message message;
  70         unsigned char command[MAX_CMD_SIZE];
  71         int ret;
  72
  73         spi_message_init(&message);
  74
  75         command[0] = MCHP23K256_CMD_WRITE;
  76         mchp23k256_addr2cmd(flash, to, command);
  77
  78         transfer[0].tx_buf = command;
  79         transfer[0].len = mchp23k256_cmdsz(flash);
  80         spi_message_add_tail(&transfer[0], &message);
  81
  82         transfer[1].tx_buf = buf;
  83         transfer[1].len = len;
  84         spi_message_add_tail(&transfer[1], &message);
  85
  86         mutex_lock(&flash->lock);
  87
  88         ret = spi_sync(flash->spi, &message);
  89
  90         mutex_unlock(&flash->lock);
  91
  92         if (ret)
  93                 return ret;
  94
  95         if (retlen && message.actual_length > sizeof(command))
  96                 *retlen += message.actual_length - sizeof(command);
  97
  98         return 0;
  99 }
 100
 101 static int mchp23k256_read(struct mtd_info *mtd, loff_t from, size_t len,
 102                            size_t *retlen, unsigned char *buf)
 103 {
 104         struct mchp23k256_flash *flash = to_mchp23k256_flash(mtd);
 105         struct spi_transfer transfer[2] = {};
 106         struct spi_message message;
 107         unsigned char command[MAX_CMD_SIZE];
 108         int ret;
 109
 110         spi_message_init(&message);
 111
 112         memset(&transfer, 0, sizeof(transfer));
 113         command[0] = MCHP23K256_CMD_READ;
 114         mchp23k256_addr2cmd(flash, from, command);
 115
 116         transfer[0].tx_buf = command;
 117         transfer[0].len = mchp23k256_cmdsz(flash);
 118         spi_message_add_tail(&transfer[0], &message);
 119
 120         transfer[1].rx_buf = buf;
 121         transfer[1].len = len;
 122         spi_message_add_tail(&transfer[1], &message);
 123
 124         mutex_lock(&flash->lock);
 125
 126         ret = spi_sync(flash->spi, &message);
 127
 128         mutex_unlock(&flash->lock);
 129
 130         if (ret)
 131                 return ret;
 132
 133         if (retlen && message.actual_length > sizeof(command))
 134                 *retlen += message.actual_length - sizeof(command);
 135
 136         return 0;
 137 }
 138
 139 /*
 140  * Set the device into sequential mode. This allows read/writes to the
 141  * entire SRAM in a single operation
 142  */
 143 static int mchp23k256_set_mode(struct spi_device *spi)
 144 {
 145         struct spi_transfer transfer = {};
 146         struct spi_message message;
 147         unsigned char command[2];
 148
 149         spi_message_init(&message);
 150
 151         command[0] = MCHP23K256_CMD_WRITE_STATUS;
 152         command[1] = MCHP23K256_MODE_SEQ;
 153
 154         transfer.tx_buf = command;
 155         transfer.len = sizeof(command);
 156         spi_message_add_tail(&transfer, &message);
 157
 158         return spi_sync(spi, &message);
 159 }
 160
 161 static const struct mchp23_caps mchp23k256_caps = {
 162         .size = SZ_32K,
 163         .addr_width = 2,
 164 };
 165
 166 static const struct mchp23_caps mchp23lcv1024_caps = {
 167         .size = SZ_128K,
 168         .addr_width = 3,
 169 };
 170
 171 static int mchp23k256_probe(struct spi_device *spi)
 172 {
 173         struct mchp23k256_flash *flash;
 174         struct flash_platform_data *data;
 175         int err;
 176
 177         flash = devm_kzalloc(&spi->dev, sizeof(*flash), GFP_KERNEL);
 178         if (!flash)
 179                 return -ENOMEM;
 180
 181         flash->spi = spi;
 182         mutex_init(&flash->lock);
 183         spi_set_drvdata(spi, flash);
 184
 185         err = mchp23k256_set_mode(spi);
 186         if (err)
 187                 return err;
 188
 189         data = dev_get_platdata(&spi->dev);
 190
 191         flash->caps = of_device_get_match_data(&spi->dev);
 192         if (!flash->caps)
 193                 flash->caps = &mchp23k256_caps;
 194
 195         mtd_set_of_node(&flash->mtd, spi->dev.of_node);
 196         flash->mtd.dev.parent   = &spi->dev;
 197         flash->mtd.type         = MTD_RAM;
 198         flash->mtd.flags        = MTD_CAP_RAM;
 199         flash->mtd.writesize    = 1;
 200         flash->mtd.size         = flash->caps->size;
 201         flash->mtd._read        = mchp23k256_read;
 202         flash->mtd._write       = mchp23k256_write;
 203
 204         err = mtd_device_register(&flash->mtd, data ? data->parts : NULL,
 205                                   data ? data->nr_parts : 0);
 206         if (err)
 207                 return err;
 208
 209         return 0;
 210 }
 211
 212 static int mchp23k256_remove(struct spi_device *spi)
 213 {
 214         struct mchp23k256_flash *flash = spi_get_drvdata(spi);
 215
 216         return mtd_device_unregister(&flash->mtd);
 217 }
 218
 219 static const struct of_device_id mchp23k256_of_table[] = {
 220         {
 221                 .compatible = "microchip,mchp23k256",
 222                 .data = &mchp23k256_caps,
 223         },
 224         {
 225                 .compatible = "microchip,mchp23lcv1024",
 226                 .data = &mchp23lcv1024_caps,
 227         },
 228         {}
 229 };
 230 MODULE_DEVICE_TABLE(of, mchp23k256_of_table);
 231
 232 static struct spi_driver mchp23k256_driver = {
 233         .driver = {
 234                 .name   = "mchp23k256",
 235                 .of_match_table = of_match_ptr(mchp23k256_of_table),
 236         },
 237         .probe          = mchp23k256_probe,
 238         .remove         = mchp23k256_remove,
 239 };
 240
 241 module_spi_driver(mchp23k256_driver);
 242
 243 MODULE_DESCRIPTION("MTD SPI driver for MCHP23K256 RAM chips");
 244 MODULE_AUTHOR("Andrew Lunn <andre@lunn.ch>");
 245 MODULE_LICENSE("GPL v2");
 246 MODULE_ALIAS("spi:mchp23k256");