nuttx/drivers/mtd/m25px.c

/****************************************************************************
 * drivers/mtd/m25px.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/* Driver for SPI-based M25P1 (128Kbit),  M25P64 (32Mbit), M25P64 (64Mbit),
 * and M25P128 (128Mbit) FLASH (and compatible).
 */

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/types.h>
#include <inttypes.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <debug.h>

#include <nuttx/kmalloc.h>
#include <nuttx/signal.h>
#include <nuttx/fs/ioctl.h>
#include <nuttx/spi/spi.h>
#include <nuttx/mtd/mtd.h>

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/* Configuration ************************************************************/

/* Per the data sheet, M25P10 parts can be driven with either SPI mode 0
 * (CPOL=0 and CPHA=0) or mode 3 (CPOL=1 and CPHA=1). But I have heard that
 * other devices can operated in mode 0 or 1.
 * So you may need to specify CONFIG_M25P_SPIMODE to
 * select the best mode for your device.
 * If CONFIG_M25P_SPIMODE is not defined, mode 0 will be used.
 */

#ifndef CONFIG_M25P_SPIMODE
#  define CONFIG_M25P_SPIMODE SPIDEV_MODE0
#endif

#ifndef CONFIG_M25P_SPIFREQUENCY
#  define CONFIG_M25P_SPIFREQUENCY 20000000
#endif

/* Various manufacturers may have produced the parts.
 * 0x20 is the manufacturer ID for the STMicro MP25x serial FLASH.
 * If, for example, you are using the a Macronix International MX25
 * serial FLASH, the correct manufacturer ID would be 0xc2.
 */

#ifndef CONFIG_M25P_MANUFACTURER
#  define CONFIG_M25P_MANUFACTURER 0x20
#endif

#ifndef CONFIG_M25P_MEMORY_TYPE
#  define CONFIG_M25P_MEMORY_TYPE  0x20
#endif

#ifndef CONFIG_MT25Q_MEMORY_TYPE
#  define CONFIG_MT25Q_MEMORY_TYPE  0xBA
#endif

/* M25P Registers ***********************************************************/

/* Identification register values */

#define M25P_MANUFACTURER          CONFIG_M25P_MANUFACTURER
#define M25P_MEMORY_TYPE           CONFIG_M25P_MEMORY_TYPE
#define MT25Q_MEMORY_TYPE          CONFIG_MT25Q_MEMORY_TYPE
#define M25P_RES_ID                0x13
#define M25P_M25P1_CAPACITY        0x11 /* 1 M-bit */
#define M25P_EN25F80_CAPACITY      0x14 /* 8 M-bit */
#define M25P_M25P16_CAPACITY       0x15 /* 16 M-bit */
#define M25P_M25P32_CAPACITY       0x16 /* 32 M-bit */
#define M25P_M25P64_CAPACITY       0x17 /* 64 M-bit */
#define M25P_M25P128_CAPACITY      0x18 /* 128 M-bit */
#define M25P_MT25Q128_CAPACITY     0x18 /* 128 M-bit */

/*  M25P1 capacity is 131,072 bytes:
 *  (4 sectors) * (32,768 bytes per sector)
 *  (512 pages) * (256 bytes per page)
 */

#define M25P_M25P1_SECTOR_SHIFT    15    /* Sector size 1 << 15 = 65,536 */
#define M25P_M25P1_NSECTORS        4
#define M25P_M25P1_PAGE_SHIFT      8     /* Page size 1 << 8 = 256 */
#define M25P_M25P1_NPAGES          512

/*  EN25F80 capacity is 1,048,576 bytes:
 *  (16 sectors) * (65,536 bytes per sector)
 *  (512 pages) * (256 bytes per page)
 */

#define M25P_EN25F80_SECTOR_SHIFT  16    /* Sector size 1 << 15 = 65,536 */
#define M25P_EN25F80_NSECTORS      16
#define M25P_EN25F80_PAGE_SHIFT    8     /* Page size 1 << 8 = 256 */
#define M25P_EN25F80_NPAGES        4096
#define M25P_EN25F80_SUBSECT_SHIFT 12   /* Sub-Sector size 1 << 12 = 4,096 */
#define M25P_EN25F80_NSUBSECTORS   256

/*  M25P16 capacity is 2,097,152 bytes:
 *  (32 sectors) * (65,536 bytes per sector)
 *  (8192 pages) * (256 bytes per page)
 */

#define M25P_M25P16_SECTOR_SHIFT   16    /* Sector size 1 << 16 = 65,536 */
#define M25P_M25P16_NSECTORS       32
#define M25P_M25P16_PAGE_SHIFT     8     /* Page size 1 << 8 = 256 */
#define M25P_M25P16_NPAGES         8192
#define M25P_M25PX16_SUBSECT_SHIFT 12   /* Sub-Sector size 1 << 12 = 4,096 */

/*  M25P32 capacity is 4,194,304 bytes:
 *  (64 sectors) * (65,536 bytes per sector)
 *  (16384 pages) * (256 bytes per page)
 */

#define M25P_M25P32_SECTOR_SHIFT   16    /* Sector size 1 << 16 = 65,536 */
#define M25P_M25P32_NSECTORS       64
#define M25P_M25P32_PAGE_SHIFT     8     /* Page size 1 << 8 = 256 */
#define M25P_M25P32_NPAGES         16384
#define M25P_M25PX32_SUBSECT_SHIFT 12    /* Sub-Sector size 1 << 12 = 4,096 */

/*  M25P64 capacity is 8,338,608 bytes:
 *  (128 sectors) * (65,536 bytes per sector)
 *  (32768 pages) * (256 bytes per page)
 */

#define M25P_M25P64_SECTOR_SHIFT   16    /* Sector size 1 << 16 = 65,536 */
#define M25P_M25P64_NSECTORS       128
#define M25P_M25P64_PAGE_SHIFT     8     /* Page size 1 << 8 = 256 */
#define M25P_M25P64_NPAGES         32768

/*  M25P128 capacity is 16,777,216 bytes:
 *  (64 sectors) * (262,144 bytes per sector)
 *  (65536 pages) * (256 bytes per page)
 */

#define M25P_M25P128_SECTOR_SHIFT  18    /* Sector size 1 << 18 = 262,144 */
#define M25P_M25P128_NSECTORS      64
#define M25P_M25P128_PAGE_SHIFT    8     /* Page size 1 << 8 = 256 */
#define M25P_M25P128_NPAGES        65536

/*  MT25Q128 capacity is 16,777,216 bytes:
 *  (256 sectors) * (65,536 bytes per sector)
 *  (65536 pages) * (256 bytes per page)
 */

#define M25P_MT25Q128_SECTOR_SHIFT  16    /* Sector size 1 << 16 = 65,536 */
#define M25P_MT25Q128_NSECTORS      256
#define M25P_MT25Q128_PAGE_SHIFT    8     /* Page size 1 << 8 = 256 */
#define M25P_MT25Q128_NPAGES        65536
#define M25P_MT25Q128_SUBSECT_SHIFT 12    /* Sub-Sector size 1 << 12 = 4,096 */

/* Instructions */

/*    Command          Value    N Description             Addr Dummy Data   */
#define M25P_WREN      0x06  /* 1 Write Enable              0   0     0     */
#define M25P_WRDI      0x04  /* 1 Write Disable             0   0     0     */
#define M25P_RDID      0x9f  /* 1 Read Identification       0   0     1-3   */
#define M25P_RDSR      0x05  /* 1 Read Status Register      0   0     >=1   */
#define M25P_WRSR      0x01  /* 1 Write Status Register     0   0     1     */
#define M25P_READ      0x03  /* 1 Read Data Bytes           3   0     >=1   */
#define M25P_FAST_READ 0x0b  /* 1 Higher speed read         3   1     >=1   */
#define M25P_PP        0x02  /* 1 Page Program              3   0     1-256 */
#define M25P_SE        0xd8  /* 1 Sector Erase              3   0     0     */
#define M25P_BE        0xc7  /* 1 Bulk Erase                0   0     0     */
#define M25P_DP        0xb9  /* 2 Deep power down           0   0     0     */
#define M25P_RES       0xab  /* 2 Read Electronic Signature 0   3     >=1   */
#define M25P_SSE       0x20  /* 3 Sub-Sector Erase          0   0     0     */

/* NOTE 1: All parts.
 * NOTE 2: M25P632/M25P64
 * NOTE 3: EN25F80.  In EN25F80 terminology, 0xd8 is a block erase and 0x20
 *         is a sector erase.
 */

/* Status register bit definitions */

#define M25P_SR_WIP            (1 << 0)                /* Bit 0: Write in progress bit */
#define M25P_SR_WEL            (1 << 1)                /* Bit 1: Write enable latch bit */
#define M25P_SR_BP_SHIFT       (2)                     /* Bits 2-4: Block protect bits */
#define M25P_SR_BP_MASK        (7 << M25P_SR_BP_SHIFT)
#  define M25P_SR_BP_NONE      (0 << M25P_SR_BP_SHIFT) /* Unprotected */
#  define M25P_SR_BP_UPPER64th (1 << M25P_SR_BP_SHIFT) /* Upper 64th */
#  define M25P_SR_BP_UPPER32nd (2 << M25P_SR_BP_SHIFT) /* Upper 32nd */
#  define M25P_SR_BP_UPPER16th (3 << M25P_SR_BP_SHIFT) /* Upper 16th */
#  define M25P_SR_BP_UPPER8th  (4 << M25P_SR_BP_SHIFT) /* Upper 8th */
#  define M25P_SR_BP_UPPERQTR  (5 << M25P_SR_BP_SHIFT) /* Upper quarter */
#  define M25P_SR_BP_UPPERHALF (6 << M25P_SR_BP_SHIFT) /* Upper half */
#  define M25P_SR_BP_ALL       (7 << M25P_SR_BP_SHIFT) /* All sectors */
                                                       /* Bits 5-6:  Unused, read zero */
#define M25P_SR_SRWD           (1 << 7)                /* Bit 7: Status register write protect */

#define M25P_DUMMY     0xa5

/****************************************************************************
 * Private Types
 ****************************************************************************/

/* This type represents the state of the MTD device.  The struct mtd_dev_s
 * must appear at the beginning of the definition so that you can freely
 * cast between pointers to struct mtd_dev_s and struct m25p_dev_s.
 */

struct m25p_dev_s
{
  struct mtd_dev_s mtd;      /* MTD interface */
  FAR struct spi_dev_s *dev; /* Saved SPI interface instance */
  uint8_t  sectorshift;      /* 16 or 18 */
  uint8_t  pageshift;        /* 8 */
  uint16_t nsectors;         /* 128 or 64 */
  uint32_t npages;           /* 32,768 or 65,536 */
#ifdef CONFIG_M25P_SUBSECTOR_ERASE
  uint8_t  subsectorshift;   /* 0, 12 or 13 (4K or 8K) */
#endif
};

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/* Helpers */

static void m25p_lock(FAR struct spi_dev_s *dev);
static inline void m25p_unlock(FAR struct spi_dev_s *dev);
static inline int m25p_readid(struct m25p_dev_s *priv);
static void m25p_waitwritecomplete(struct m25p_dev_s *priv);
static void m25p_writeenable(struct m25p_dev_s *priv);
static inline void m25p_sectorerase(struct m25p_dev_s *priv,
                                    off_t offset,
                                    uint8_t type);
static inline int  m25p_bulkerase(struct m25p_dev_s *priv);
static inline void m25p_pagewrite(struct m25p_dev_s *priv,
                                  FAR const uint8_t *buffer,
                                  off_t offset);

/* MTD driver methods */

static int m25p_erase(FAR struct mtd_dev_s *dev,
                      off_t startblock,
                      size_t nblocks);
static ssize_t m25p_bread(FAR struct mtd_dev_s *dev,
                          off_t startblock,
                          size_t nblocks,
                          FAR uint8_t *buf);
static ssize_t m25p_bwrite(FAR struct mtd_dev_s *dev,
                           off_t startblock,
                           size_t nblocks,
                           FAR const uint8_t *buf);
static ssize_t m25p_read(FAR struct mtd_dev_s *dev,
                         off_t offset, size_t nbytes,
                         FAR uint8_t *buffer);
#ifdef CONFIG_MTD_BYTE_WRITE
static ssize_t m25p_write(FAR struct mtd_dev_s *dev,
                          off_t offset,
                          size_t nbytes,
                          FAR const uint8_t *buffer);
#endif
static int m25p_ioctl(FAR struct mtd_dev_s *dev,
                      int cmd,
                      unsigned long arg);

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: m25p_lock
 ****************************************************************************/

static void m25p_lock(FAR struct spi_dev_s *dev)
{
  /* On SPI buses where there are multiple devices, it will be necessary to
   * lock SPI to have exclusive access to the buses for a sequence of
   * transfers.  The bus should be locked before the chip is selected.
   *
   * This is a blocking call and will not return until we have exclusive
   * access to the SPI bus.  We will retain that exclusive access until the
   * bus is unlocked.
   */

  SPI_LOCK(dev, true);

  /* After locking the SPI bus, the we also need call the setfrequency,
   * setbits, and setmode methods to make sure that the SPI is properly
   * configured for the device.
   * If the SPI bus is being shared, then it may have been left in an
   * incompatible state.
   */

  SPI_SETMODE(dev, CONFIG_M25P_SPIMODE);
  SPI_SETBITS(dev, 8);
  SPI_HWFEATURES(dev, 0);
  SPI_SETFREQUENCY(dev, CONFIG_M25P_SPIFREQUENCY);
}

/****************************************************************************
 * Name: m25p_unlock
 ****************************************************************************/

static inline void m25p_unlock(FAR struct spi_dev_s *dev)
{
  SPI_LOCK(dev, false);
}

/****************************************************************************
 * Name: m25p_readid
 ****************************************************************************/

static inline int m25p_readid(struct m25p_dev_s *priv)
{
  uint16_t manufacturer;
  uint16_t memory;
  uint16_t capacity;

  finfo("priv: %p\n", priv);

  /* Lock the SPI bus, configure the bus, and select this FLASH part. */

  m25p_lock(priv->dev);
  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), true);

  /* Send the "Read ID (RDID)" command and read the first three ID bytes */

  SPI_SEND(priv->dev, M25P_RDID);
  manufacturer = SPI_SEND(priv->dev, M25P_DUMMY);
  memory       = SPI_SEND(priv->dev, M25P_DUMMY);
  capacity     = SPI_SEND(priv->dev, M25P_DUMMY);

  /* Deselect the FLASH and unlock the bus */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), false);
  m25p_unlock(priv->dev);

  finfo("manufacturer: %02x memory: %02x capacity: %02x\n",
        manufacturer, memory, capacity);

  /* Check for a valid manufacturer and memory type */

  if (manufacturer == M25P_MANUFACTURER && memory == M25P_MEMORY_TYPE)
    {
      /* Okay.. is it a FLASH capacity that we understand? */

#ifdef CONFIG_M25P_SUBSECTOR_ERASE
      priv->subsectorshift = 0;
#endif

      if (capacity == M25P_M25P1_CAPACITY)
        {
          /* Save the FLASH geometry */

          priv->sectorshift    = M25P_M25P1_SECTOR_SHIFT;
          priv->nsectors       = M25P_M25P1_NSECTORS;
          priv->pageshift      = M25P_M25P1_PAGE_SHIFT;
          priv->npages         = M25P_M25P1_NPAGES;
          return OK;
        }
      else if (capacity == M25P_EN25F80_CAPACITY)
        {
          /* Save the FLASH geometry */

          priv->pageshift      = M25P_EN25F80_PAGE_SHIFT;
          priv->npages         = M25P_EN25F80_NPAGES;
          priv->sectorshift    = M25P_EN25F80_SECTOR_SHIFT;
          priv->nsectors       = M25P_EN25F80_NSECTORS;
#ifdef CONFIG_M25P_SUBSECTOR_ERASE
          priv->subsectorshift = M25P_EN25F80_SUBSECT_SHIFT;
#endif
          return OK;
        }
      else if (capacity == M25P_M25P16_CAPACITY)
        {
          /* Save the FLASH geometry */

          priv->sectorshift    = M25P_M25P16_SECTOR_SHIFT;
          priv->nsectors       = M25P_M25P16_NSECTORS;
          priv->pageshift      = M25P_M25P16_PAGE_SHIFT;
          priv->npages         = M25P_M25P16_NPAGES;
#ifdef CONFIG_M25P_SUBSECTOR_ERASE
          priv->subsectorshift = M25P_M25PX16_SUBSECT_SHIFT;
#endif
          return OK;
        }
      else if (capacity == M25P_M25P32_CAPACITY)
        {
          /* Save the FLASH geometry */

          priv->sectorshift    = M25P_M25P32_SECTOR_SHIFT;
          priv->nsectors       = M25P_M25P32_NSECTORS;
          priv->pageshift      = M25P_M25P32_PAGE_SHIFT;
          priv->npages         = M25P_M25P32_NPAGES;
#ifdef CONFIG_M25P_SUBSECTOR_ERASE
          priv->subsectorshift = M25P_M25PX32_SUBSECT_SHIFT;
#endif
          return OK;
        }
      else if (capacity == M25P_M25P64_CAPACITY)
        {
          /* Save the FLASH geometry */

          priv->sectorshift    = M25P_M25P64_SECTOR_SHIFT;
          priv->nsectors       = M25P_M25P64_NSECTORS;
          priv->pageshift      = M25P_M25P64_PAGE_SHIFT;
          priv->npages         = M25P_M25P64_NPAGES;
          return OK;
        }
      else if (capacity == M25P_M25P128_CAPACITY)
        {
          /* Save the FLASH geometry */

          priv->sectorshift    = M25P_M25P128_SECTOR_SHIFT;
          priv->nsectors       = M25P_M25P128_NSECTORS;
          priv->pageshift      = M25P_M25P128_PAGE_SHIFT;
          priv->npages         = M25P_M25P128_NPAGES;
          return OK;
        }
    }
  else if (manufacturer == M25P_MANUFACTURER && memory == MT25Q_MEMORY_TYPE)
    {
      /* Also okay.. is it a FLASH capacity that we understand? */

#ifdef CONFIG_M25P_SUBSECTOR_ERASE
      priv->subsectorshift = 0;
#endif
      if (capacity == M25P_MT25Q128_CAPACITY)
        {
          /* Save the FLASH geometry */

          priv->sectorshift    = M25P_MT25Q128_SECTOR_SHIFT;
          priv->nsectors       = M25P_MT25Q128_NSECTORS;
          priv->pageshift      = M25P_MT25Q128_PAGE_SHIFT;
          priv->npages         = M25P_MT25Q128_NPAGES;
#ifdef CONFIG_M25P_SUBSECTOR_ERASE
          priv->subsectorshift = M25P_MT25Q128_SUBSECT_SHIFT;
#endif
          return OK;
        }
    }

  return -ENODEV;
}

/****************************************************************************
 * Name: m25p_waitwritecomplete
 ****************************************************************************/

static void m25p_waitwritecomplete(struct m25p_dev_s *priv)
{
  uint8_t status;

  /* Loop as long as the memory is busy with a write cycle */

  do
    {
      /* Select this FLASH part */

      SPI_SELECT(priv->dev, SPIDEV_FLASH(0), true);

      /* Send "Read Status Register (RDSR)" command */

      SPI_SEND(priv->dev, M25P_RDSR);

      /* Send a dummy byte to generate the clock needed to shift out the
       * status
       */

      status = SPI_SEND(priv->dev, M25P_DUMMY);

      /* Deselect the FLASH */

      SPI_SELECT(priv->dev, SPIDEV_FLASH(0), false);

      /* Given that writing could take up to few tens of milliseconds, and
       * erasing could take more.
       * The following short delay in the "busy" case will allow other
       * peripherals to access the SPI bus.
       */

      if ((status & M25P_SR_WIP) != 0)
        {
          m25p_unlock(priv->dev);
          nxsig_usleep(1000);
          m25p_lock(priv->dev);
        }
    }
  while ((status & M25P_SR_WIP) != 0);

  finfo("Complete\n");
}

/****************************************************************************
 * Name:  m25p_writeenable
 ****************************************************************************/

static void m25p_writeenable(struct m25p_dev_s *priv)
{
  /* Select this FLASH part */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), true);

  /* Send "Write Enable (WREN)" command */

  SPI_SEND(priv->dev, M25P_WREN);

  /* Deselect the FLASH */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), false);
  finfo("Enabled\n");
}

/****************************************************************************
 * Name:  m25p_sectorerase
 ****************************************************************************/

static void m25p_sectorerase(struct m25p_dev_s *priv,
                             off_t sector,
                             uint8_t type)
{
  off_t offset;

#ifdef CONFIG_M25P_SUBSECTOR_ERASE
  if (priv->subsectorshift > 0)
    {
      offset = sector << priv->subsectorshift;
    }
  else
#endif
    {
      offset = sector << priv->sectorshift;
    }

  finfo("sector: %08lx\n", (long)sector);

  /* Wait for any preceding write to complete. We could simplify things by
   * perform this wait at the end of each write operation (rather than at
   * the beginning of ALL operations), but have the wait first will slightly
   * improve performance.
   */

  m25p_waitwritecomplete(priv);

  /* Send write enable instruction */

  m25p_writeenable(priv);

  /* Select this FLASH part */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), true);

  /* Send the "Sector Erase (SE)" or Sub-Sector Erase (SSE) instruction
   * that was passed in as the erase type.
   */

  SPI_SEND(priv->dev, type);

  /* Send the sector offset high byte first.  For all of the supported
   * parts, the sector number is completely contained in the first byte
   * and the values used in the following two bytes don't really matter.
   */

  SPI_SEND(priv->dev, (offset >> 16) & 0xff);
  SPI_SEND(priv->dev, (offset >> 8) & 0xff);
  SPI_SEND(priv->dev, offset & 0xff);

  /* Deselect the FLASH */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), false);
  finfo("Erased\n");
}

/****************************************************************************
 * Name:  m25p_bulkerase
 ****************************************************************************/

static inline int m25p_bulkerase(struct m25p_dev_s *priv)
{
  finfo("priv: %p\n", priv);

  /* Wait for any preceding write to complete.  We could simplify things by
   * perform this wait at the end of each write operation (rather than at
   * the beginning of ALL operations), but have the wait first will slightly
   * improve performance.
   */

  m25p_waitwritecomplete(priv);

  /* Send write enable instruction */

  m25p_writeenable(priv);

  /* Select this FLASH part */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), true);

  /* Send the "Bulk Erase (BE)" instruction */

  SPI_SEND(priv->dev, M25P_BE);

  /* Deselect the FLASH */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), false);
  finfo("Return: OK\n");
  return OK;
}

/****************************************************************************
 * Name:  m25p_pagewrite
 ****************************************************************************/

static inline void m25p_pagewrite(struct m25p_dev_s *priv,
                                  FAR const uint8_t *buffer,
                                  off_t page)
{
  off_t offset = page << priv->pageshift;

  finfo("page: %08lx offset: %08lx\n", (long)page, (long)offset);

  /* Wait for any preceding write to complete.  We could simplify things by
   * perform this wait at the end of each write operation (rather than at
   * the beginning of ALL operations), but have the wait first will slightly
   * improve performance.
   */

  m25p_waitwritecomplete(priv);

  /* Enable the write access to the FLASH */

  m25p_writeenable(priv);

  /* Select this FLASH part */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), true);

  /* Send "Page Program (PP)" command */

  SPI_SEND(priv->dev, M25P_PP);

  /* Send the page offset high byte first. */

  SPI_SEND(priv->dev, (offset >> 16) & 0xff);
  SPI_SEND(priv->dev, (offset >> 8) & 0xff);
  SPI_SEND(priv->dev, offset & 0xff);

  /* Then write the specified number of bytes */

  SPI_SNDBLOCK(priv->dev, buffer, 1 << priv->pageshift);

  /* Deselect the FLASH: Chip Select high */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), false);
  finfo("Written\n");
}

/****************************************************************************
 * Name:  m25p_bytewrite
 ****************************************************************************/

#ifdef CONFIG_MTD_BYTE_WRITE
static inline void m25p_bytewrite(struct m25p_dev_s *priv,
                                  FAR const uint8_t *buffer,
                                  off_t offset,
                                  uint16_t count)
{
  finfo("offset: %08lx  count:%d\n", (long)offset, count);

  /* Wait for any preceding write to complete.  We could simplify things by
   * perform this wait at the end of each write operation (rather than at
   * the beginning of ALL operations), but have the wait first will slightly
   * improve performance.
   */

  m25p_waitwritecomplete(priv);

  /* Enable the write access to the FLASH */

  m25p_writeenable(priv);

  /* Select this FLASH part */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), true);

  /* Send "Page Program (PP)" command */

  SPI_SEND(priv->dev, M25P_PP);

  /* Send the page offset high byte first. */

  SPI_SEND(priv->dev, (offset >> 16) & 0xff);
  SPI_SEND(priv->dev, (offset >> 8) & 0xff);
  SPI_SEND(priv->dev, offset & 0xff);

  /* Then write the specified number of bytes */

  SPI_SNDBLOCK(priv->dev, buffer, count);

  /* Deselect the FLASH: Chip Select high */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), false);
  finfo("Written\n");
}
#endif

/****************************************************************************
 * Name: m25p_erase
 ****************************************************************************/

static int m25p_erase(FAR struct mtd_dev_s *dev,
                      off_t startblock,
                      size_t nblocks)
{
  FAR struct m25p_dev_s *priv = (FAR struct m25p_dev_s *)dev;
  size_t blocksleft = nblocks;

  finfo("startblock: %08lx nblocks: %d\n", (long)startblock, (int)nblocks);

  /* Lock access to the SPI bus until we complete the erase */

  m25p_lock(priv->dev);
  while (blocksleft > 0)
    {
#ifdef CONFIG_M25P_SUBSECTOR_ERASE
      size_t sectorboundry;
      size_t blkper;

      /* If we have a smaller erase size, then we will find as many full
       * sector erase blocks as possible to speed up the process instead of
       * erasing everything in smaller chunks.
       */

      if (priv->subsectorshift > 0)
        {
          blkper = 1 << (priv->sectorshift - priv->subsectorshift);
          sectorboundry = (startblock + blkper - 1) / blkper;
          sectorboundry *= blkper;

          /* If we are on a sector boundary and have at least a full sector
           * of blocks left to erase, then we can do a full sector erase.
           */

          if (startblock == sectorboundry && blocksleft >= blkper)
            {
              /* Do a full sector erase */

              m25p_sectorerase(priv, startblock, M25P_SE);
              startblock += blkper;
              blocksleft -= blkper;
              continue;
            }
          else
            {
              /* Just do a sub-sector erase */

              m25p_sectorerase(priv, startblock, M25P_SSE);
              startblock++;
              blocksleft--;
              continue;
            }
        }
#endif

      /* Not using sub-sector erase.  Erase each full sector */

      m25p_sectorerase(priv, startblock, M25P_SE);
      startblock++;
      blocksleft--;
    }

  m25p_unlock(priv->dev);
  return (int)nblocks;
}

/****************************************************************************
 * Name: m25p_bread
 ****************************************************************************/

static ssize_t m25p_bread(FAR struct mtd_dev_s *dev, off_t startblock,
                          size_t nblocks,
                          FAR uint8_t *buffer)
{
  FAR struct m25p_dev_s *priv = (FAR struct m25p_dev_s *)dev;
  ssize_t nbytes;

  finfo("startblock: %08lx nblocks: %d\n", (long)startblock, (int)nblocks);

  /* On this device, we can handle the block read just like the byte-oriented
   * read
   */

  nbytes = m25p_read(dev, startblock << priv->pageshift,
                     nblocks << priv->pageshift, buffer);
  if (nbytes > 0)
    {
      return nbytes >> priv->pageshift;
    }

  return (int)nbytes;
}

/****************************************************************************
 * Name: m25p_bwrite
 ****************************************************************************/

static ssize_t m25p_bwrite(FAR struct mtd_dev_s *dev, off_t startblock,
                           size_t nblocks,
                           FAR const uint8_t *buffer)
{
  FAR struct m25p_dev_s *priv = (FAR struct m25p_dev_s *)dev;
  size_t blocksleft = nblocks;
  size_t pagesize = 1 << priv->pageshift;

  finfo("startblock: %08lx nblocks: %d\n", (long)startblock, (int)nblocks);

  /* Lock the SPI bus and write each page to FLASH */

  m25p_lock(priv->dev);
  while (blocksleft-- > 0)
    {
      m25p_pagewrite(priv, buffer, startblock);
      buffer += pagesize;
      startblock++;
    }

  m25p_unlock(priv->dev);
  return nblocks;
}

/****************************************************************************
 * Name: m25p_read
 ****************************************************************************/

static ssize_t m25p_read(FAR struct mtd_dev_s *dev,
                         off_t offset,
                         size_t nbytes,
                         FAR uint8_t *buffer)
{
  FAR struct m25p_dev_s *priv = (FAR struct m25p_dev_s *)dev;

  finfo("offset: %08lx nbytes: %d\n", (long)offset, (int)nbytes);

  /* Lock the SPI bus NOW because the following call must be executed with
   * the bus locked.
   */

  m25p_lock(priv->dev);

  /* Wait for any preceding write to complete.  We could simplify things by
   * perform this wait at the end of each write operation (rather than at
   * the beginning of ALL operations), but have the wait first will slightly
   * improve performance.
   */

  m25p_waitwritecomplete(priv);

  /* Select this FLASH part */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), true);

  /* Send "Read from Memory" instruction */

  SPI_SEND(priv->dev, M25P_READ);

  /* Send the page offset high byte first. */

  SPI_SEND(priv->dev, (offset >> 16) & 0xff);
  SPI_SEND(priv->dev, (offset >> 8) & 0xff);
  SPI_SEND(priv->dev, offset & 0xff);

  /* Then read all of the requested bytes */

  SPI_RECVBLOCK(priv->dev, buffer, nbytes);

  /* Deselect the FLASH and unlock the SPI bus */

  SPI_SELECT(priv->dev, SPIDEV_FLASH(0), false);
  m25p_unlock(priv->dev);

  finfo("return nbytes: %d\n", (int)nbytes);
  return nbytes;
}

/****************************************************************************
 * Name: m25p_write
 ****************************************************************************/

#ifdef CONFIG_MTD_BYTE_WRITE
static ssize_t m25p_write(FAR struct mtd_dev_s *dev,
                          off_t offset,
                          size_t nbytes,
                          FAR const uint8_t *buffer)
{
  FAR struct m25p_dev_s *priv = (FAR struct m25p_dev_s *)dev;
  int    startpage;
  int    endpage;
  int    count;
  int    index;
  int    pagesize;
  int    bytestowrite;

  finfo("offset: %08lx nbytes: %d\n", (long)offset, (int)nbytes);

  /* We must test if the offset + count crosses one or more pages
   * and perform individual writes.  The devices can only write in
   * page increments.
   */

  startpage = offset / (1 << priv->pageshift);
  endpage = (offset + nbytes) / (1 << priv->pageshift);

  m25p_lock(priv->dev);
  if (startpage == endpage)
    {
      /* All bytes within one programmable page.  Just do the write. */

      m25p_bytewrite(priv, buffer, offset, nbytes);
    }
  else
    {
      /* Write the 1st partial-page */

      count = nbytes;
      pagesize = (1 << priv->pageshift);
      bytestowrite = pagesize - (offset & (pagesize - 1));
      m25p_bytewrite(priv, buffer, offset, bytestowrite);

      /* Update offset and count */

      offset += bytestowrite;
      count -=  bytestowrite;
      index = bytestowrite;

      /* Write full pages */

      while (count >= pagesize)
        {
          m25p_bytewrite(priv, &buffer[index], offset, pagesize);

          /* Update offset and count */

          offset += pagesize;
          count -= pagesize;
          index += pagesize;
        }

      /* Now write any partial page at the end */

      if (count > 0)
        {
          m25p_bytewrite(priv, &buffer[index], offset, count);
        }
    }

  m25p_unlock(priv->dev);
  return nbytes;
}
#endif /* CONFIG_MTD_BYTE_WRITE */

/****************************************************************************
 * Name: m25p_ioctl
 ****************************************************************************/

static int m25p_ioctl(FAR struct mtd_dev_s *dev, int cmd, unsigned long arg)
{
  FAR struct m25p_dev_s *priv = (FAR struct m25p_dev_s *)dev;
  int ret = -EINVAL; /* Assume good command with bad parameters */

  finfo("cmd: %d \n", cmd);

  switch (cmd)
    {
      case MTDIOC_GEOMETRY:
        {
          FAR struct mtd_geometry_s *geo = (FAR struct mtd_geometry_s *)
                                           ((uintptr_t)arg);
          if (geo)
            {
              /* Populate the geometry structure with information need to
               * know the capacity and how to access the device.
               *
               * NOTE:
               * that the device is treated as though it where just an array
               * of fixed size blocks.
               * That is most likely not true, but the client will expect the
               * device logic to do whatever is necessary to make it appear
               * so.
               */

              geo->blocksize = (1 << priv->pageshift);
#ifdef CONFIG_M25P_SUBSECTOR_ERASE
              if (priv->subsectorshift > 0)
                {
                  geo->erasesize    = (1 << priv->subsectorshift);
                  geo->neraseblocks = priv->nsectors *
                                     (1 << (priv->sectorshift -
                                      priv->subsectorshift));
                }
              else
#endif
                {
                  geo->erasesize    = (1 << priv->sectorshift);
                  geo->neraseblocks = priv->nsectors;
                }

              ret = OK;

              finfo("blocksize: %" PRId32 " erasesize: %" PRId32
                    " neraseblocks: %" PRId32 "\n",
                    geo->blocksize, geo->erasesize, geo->neraseblocks);
            }
        }
        break;

      case MTDIOC_BULKERASE:
        {
            /* Erase the entire device */

            m25p_lock(priv->dev);
            ret = m25p_bulkerase(priv);
            m25p_unlock(priv->dev);
        }
        break;

      case MTDIOC_XIPBASE:
      default:
        ret = -ENOTTY; /* Bad command */
        break;
    }

  finfo("return %d\n", ret);
  return ret;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: m25p_initialize
 *
 * Description:
 *   Create an initialize MTD device instance.
 *   MTD devices are not registered in the file system, but are created as
 *   instances that can be bound to other functions (such as a block or
 *   character driver front end).
 *
 ****************************************************************************/

FAR struct mtd_dev_s *m25p_initialize(FAR struct spi_dev_s *dev)
{
  FAR struct m25p_dev_s *priv;
  int ret;

  finfo("dev: %p\n", dev);

  /* Allocate a state structure (we allocate the structure instead of using
   * a fixed, static allocation so that we can handle multiple FLASH devices.
   * The current implementation would handle only one FLASH part per SPI
   * device (only because of the SPIDEV_FLASH(0) definition) and so would
   * have to be extended to handle multiple FLASH parts on the same SPI bus.
   */

  priv = (FAR struct m25p_dev_s *)kmm_zalloc(sizeof(struct m25p_dev_s));
  if (priv)
    {
      /* Initialize the allocated structure. (unsupported methods were
       * nullified by kmm_zalloc).
       */

      priv->mtd.erase  = m25p_erase;
      priv->mtd.bread  = m25p_bread;
      priv->mtd.bwrite = m25p_bwrite;
      priv->mtd.read   = m25p_read;
#ifdef CONFIG_MTD_BYTE_WRITE
      priv->mtd.write  = m25p_write;
#endif
      priv->mtd.ioctl  = m25p_ioctl;
      priv->mtd.name   = "m25px";
      priv->dev        = dev;

      /* Deselect the FLASH */

      SPI_SELECT(dev, SPIDEV_FLASH(0), false);

      /* Identify the FLASH chip and get its capacity */

      ret = m25p_readid(priv);
      if (ret != OK)
        {
          /* Unrecognized!
           * Discard all of that work we just did and return NULL
           */

          ferr("ERROR: Unrecognized\n");
          kmm_free(priv);
          return NULL;
        }
    }

  /* Return the implementation-specific state structure as the MTD device */

  finfo("Return %p\n", priv);
  return (FAR struct mtd_dev_s *)priv;
}