Re: [PATCH 4/6] mtd: m25p80: change the read function to read page by page

[Grant Likely <grant.likely@secretlab.ca>]

On Tue, Jul 20, 2010 at 10:08:23AM +0800, Mingkai Hu wrote:
> For Freescale's eSPI controller, the max transaction length one time
> is limitted by the SPCOM[TRANSLEN] field which is 0x10000. 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 change the read function
> if used the eSPI controller.
> 
> Signed-off-by: Mingkai Hu <Mingkai.hu@freescale.com>
> ---
>  drivers/mtd/devices/m25p80.c |   18 ++++++++++++++----
>  1 files changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
> index 81e49a9..6cbe6b1 100644
> --- a/drivers/mtd/devices/m25p80.c
> +++ b/drivers/mtd/devices/m25p80.c
> @@ -317,6 +317,7 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
>  	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",
> @@ -341,7 +342,6 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
>  	spi_message_add_tail(&t[0], &m);
>  
>  	t[1].rx_buf = buf;
> -	t[1].len = len;
>  	spi_message_add_tail(&t[1], &m);
>  
>  	/* Byte count starts at zero. */
> @@ -364,11 +364,21 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
>  
>  	/* Set up the write data buffer. */
>  	flash->command[0] = OPCODE_READ;
> -	m25p_addr2cmd(flash, from, flash->command);
>  
> -	spi_sync(flash->spi, &m);
> +	for (i = page_size; i < len; i += page_size) {
> +		page_size = len - i;
> +		if (page_size > flash->page_size)
> +			page_size = flash->page_size;
>  
> -	*retlen = m.actual_length - m25p_cmdsz(flash) - FAST_READ_DUMMY_BYTE;
> +		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;
> +	}

This patch seems to cripple all users just because eSPI cannot handle it.  Am I reading it wrong?

>  
>  	mutex_unlock(&flash->lock);
>  
> -- 
> 1.6.4
> 
>