[PATCH v2 4/6] mtd: m25p80: add a read function to read page by page

[Grant Likely]

[adding David Woodhouse]

(Btw, you should cc: David Woodhouse and the mtd list on the MTD patches).

On Mon, Aug 2, 2010 at 1:52 AM, Mingkai Hu <Mingkai.hu at freescale.com> wrote:
> For Freescale's eSPI controller, the max transaction length one time
> is limitted by the SPCOM[TRANSLEN] field which is 0xFFFF. When used
> mkfs.ext2 command to create ext2 filesystem on the flash, the read
> length will exceed the max value of the SPCOM[TRANSLEN] field, so
> change the read function to read page by page.
>
> For other SPI flash driver, also needed to supply the read function
> if used the eSPI controller.
>
> Signed-off-by: Mingkai Hu <Mingkai.hu at freescale.com>

This one bothers me, but I can't put my finger on it.  The flag feels
like a controller specific hack.  David, can you take a look at this
patch?

g.

> ---
>
> v2:
>  - Add SPI_MASTER_TRANS_LIMIT flag to indicate the master's trans length
>   limitation, so the MTD driver can select the correct transfer behaviour
>   at driver probe time
>
>  drivers/mtd/devices/m25p80.c |   78 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/spi/spi_fsl_espi.c   |    1 +
>  include/linux/spi/spi.h      |    1 +
>  3 files changed, 80 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
> index 5f00075..30e4568 100644
> --- a/drivers/mtd/devices/m25p80.c
> +++ b/drivers/mtd/devices/m25p80.c
> @@ -376,6 +376,81 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
>  }
>
>  /*
> + * Read an address range from the flash chip page by page.
> + * Some controller has transaction length limitation such as the
> + * Freescale's eSPI controller can only trasmit 0xFFFF bytes one
> + * time, so we have to read page by page if the len is more than
> + * the limitation.
> + */
> +static int m25p80_page_read(struct mtd_info *mtd, loff_t from, size_t len,
> +       size_t *retlen, u_char *buf)
> +{
> +       struct m25p *flash = mtd_to_m25p(mtd);
> +       struct spi_transfer t[2];
> +       struct spi_message m;
> +       u32 i, page_size = 0;
> +
> +       DEBUG(MTD_DEBUG_LEVEL2, "%s: %s %s 0x%08x, len %zd\n",
> +                       dev_name(&flash->spi->dev), __func__, "from",
> +                       (u32)from, len);
> +
> +       /* sanity checks */
> +       if (!len)
> +               return 0;
> +
> +       if (from + len > flash->mtd.size)
> +               return -EINVAL;
> +
> +       spi_message_init(&m);
> +       memset(t, 0, (sizeof t));
> +
> +       /* NOTE:
> +        * OPCODE_FAST_READ (if available) is faster.
> +        * Should add 1 byte DUMMY_BYTE.
> +        */
> +       t[0].tx_buf = flash->command;
> +       t[0].len = m25p_cmdsz(flash) + FAST_READ_DUMMY_BYTE;
> +       spi_message_add_tail(&t[0], &m);
> +
> +       t[1].rx_buf = buf;
> +       spi_message_add_tail(&t[1], &m);
> +
> +       /* Byte count starts at zero. */
> +       if (retlen)
> +               *retlen = 0;
> +
> +       mutex_lock(&flash->lock);
> +
> +       /* Wait till previous write/erase is done. */
> +       if (wait_till_ready(flash)) {
> +               /* REVISIT status return?? */
> +               mutex_unlock(&flash->lock);
> +               return 1;
> +       }
> +
> +       /* Set up the write data buffer. */
> +       flash->command[0] = OPCODE_READ;
> +
> +       for (i = page_size; i < len; i += page_size) {
> +               page_size = len - i;
> +               if (page_size > flash->page_size)
> +                       page_size = flash->page_size;
> +               m25p_addr2cmd(flash, from + i, flash->command);
> +               t[1].len = page_size;
> +               t[1].rx_buf = buf + i;
> +
> +               spi_sync(flash->spi, &m);
> +
> +               *retlen += m.actual_length - m25p_cmdsz(flash)
> +                       - FAST_READ_DUMMY_BYTE;
> +       }
> +
> +       mutex_unlock(&flash->lock);
> +
> +       return 0;
> +}
> +
> +/*
>  * Write an address range to the flash chip.  Data must be written in
>  * FLASH_PAGESIZE chunks.  The address range may be any size provided
>  * it is within the physical boundaries.
> @@ -877,6 +952,9 @@ static int __devinit m25p_probe(struct spi_device *spi)
>        flash->mtd.erase = m25p80_erase;
>        flash->mtd.read = m25p80_read;
>
> +       if (spi->master->flags & SPI_MASTER_TRANS_LIMIT)
> +               flash->mtd.read = m25p80_page_read;
> +
>        /* sst flash chips use AAI word program */
>        if (info->jedec_id >> 16 == 0xbf)
>                flash->mtd.write = sst_write;
> diff --git a/drivers/spi/spi_fsl_espi.c b/drivers/spi/spi_fsl_espi.c
> index 61987cf..e15b7dc 100644
> --- a/drivers/spi/spi_fsl_espi.c
> +++ b/drivers/spi/spi_fsl_espi.c
> @@ -470,6 +470,7 @@ static struct spi_master * __devinit fsl_espi_probe(struct device *dev,
>                goto err_probe;
>
>        master->setup = fsl_espi_setup;
> +       master->flags = SPI_MASTER_TRANS_LIMIT;
>
>        mpc8xxx_spi = spi_master_get_devdata(master);
>        mpc8xxx_spi->spi_do_one_msg = fsl_espi_do_one_msg;
> diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
> index af56071..0729cbd 100644
> --- a/include/linux/spi/spi.h
> +++ b/include/linux/spi/spi.h
> @@ -261,6 +261,7 @@ struct spi_master {
>  #define SPI_MASTER_HALF_DUPLEX BIT(0)          /* can't do full duplex */
>  #define SPI_MASTER_NO_RX       BIT(1)          /* can't do buffer read */
>  #define SPI_MASTER_NO_TX       BIT(2)          /* can't do buffer write */
> +#define SPI_MASTER_TRANS_LIMIT BIT(3)          /* have trans length limit */
>
>        /* Setup mode and clock, etc (spi driver may call many times).
>         *
> --
> 1.6.4
>
>
>



-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.