On Mon, Jul 26, 2010 at 1:33 AM, Hu Mingkai-B21284 <b21...@freescale.com> wrote: > > >> -----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,
And it is multiplatform-unfriendly. > are there other ways? You need to select the correct transfer behaviour at driver probe time. You'll need a way to indicate that the spi_master isn't able to handle your transfer request. I'd need to think about it more to come up with a concrete suggestion. g. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
