> -----Original Message-----
> From: Grant Likely [mailto:glik...@secretlab.ca] On Behalf Of
> Grant Likely
> Sent: Monday, July 26, 2010 8:30 AM
> To: Hu Mingkai-B21284
> Cc: linuxppc-...@ozlabs.org; ga...@kernel.crashing.org; Zang
> Roy-R61911
> Subject: Re: [PATCH 4/6] mtd: m25p80: change the read
> function to read page by page
>
> 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...@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?
>
You're right, this will cripple all users.
At first, I want to contain this specific code with CONFIG_SPI_FSL_ESPI
option,
or register a specific read function like:
#ifdef CONFIG_SPI_FSL_ESPI
flash->mtd.read = m25p80_read_espi;
#endif
but this will make the code looks arguly, are there other ways?
Thanks,
Mingkai
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