Re: [PATCH 6/8] mtd: nand: mxc: Add own write_page

Sascha Hauer
2018-01-17T10:40:25Z

Hi Miquel,

On Sat, Jan 13, 2018 at 05:25:51PM +0100, Miquel Raynal wrote:
> Hi Sascha,
>
> On Tue, 9 Jan 2018 11:11:46 +0100
> Sascha Hauer <s.hauer@pengutronix.de> wrote:
>
> > Now that we have our own read_page function add a write_page function
> > for consistency aswell. This can be a lot easier than the generic
> > function since we do not have to iterate over subpages but can write
> > the whole page at once. Also add write_page_raw and write_oob for
> > proper raw and oob write support.
> >
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> > drivers/mtd/nand/mxc_nand.c | 56
> > +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56
> > insertions(+)
> >
> > diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
> > index 83bb01ab7079..6fbf98851a96 100644
> > --- a/drivers/mtd/nand/mxc_nand.c
> > +++ b/drivers/mtd/nand/mxc_nand.c
> > @@ -893,6 +893,59 @@ static int mxc_nand_read_oob(struct mtd_info
> > *mtd, struct nand_chip *chip, page);
> > }
> >
> > +static int __mxc_nand_write_page(struct mtd_info *mtd, struct
> > nand_chip *chip,
> > + const uint8_t *buf, int
> > oob_required, int page) +{
> > + struct mxc_nand_host *host = nand_get_controller_data(chip);
> > +
> > + host->devtype_data->send_cmd(host, NAND_CMD_SEQIN, false);
> > + mxc_do_addr_cycle(mtd, 0, page);
> > +
> > + memcpy32_toio(host->main_area0, buf, mtd->writesize);
> > + copy_spare(mtd, false, chip->oob_poi);
>
> If I remember correctly, there was a "spare only" mechanism to avoid
> doing full page read/write when unnecessary. What about using it here
> when (buf == NULL && oob_required)?

You are probably referring to the SP_EN bit in the NAND_FLASH_CONFIG1
register right? This is described as:

> NAND Flash spare enable. This bit determines whether host reads/writes
> are to NAND Flash spare data only or NAND Flash main and spare data.
> This feature is supported only with memories with 1/2K page size.
> Note: There is no ECC in this mode of operation.
> 0 NAND Flash main and spare data is enabled
> 1 NAND Flash spare only data is enabled

At least the i.MX25 has the limitation of 1/2k page size for this
feature. It's not in the i.MX27 manual. I don't know if the i.MX27
documentation is inaccurate or if this limitation is there already.

Anyway, I don't think it's worth optimizing for this case given that
we still need to support a full page write for 2k pages (which should
be much more widespread nowadays than the 512b page size NANDs).

Sascha

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