i.MX25 NFC with 8 bit ecc strength
Baruch Siach
baruch at tkos.co.il
Tue Apr 21 02:20:40 PDT 2015
Hi Uwe,
On Tue, Apr 21, 2015 at 11:05:07AM +0200, Uwe Kleine-König wrote:
> On Tue, Apr 21, 2015 at 11:58:08AM +0300, Baruch Siach wrote:
> > On Tue, Apr 21, 2015 at 09:39:36AM +0200, Uwe Kleine-König wrote:
> > > While understanding the problem I produced the following (untested)
> > > patch:
> > >
> > > diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
> > > index dca63a70e783..fc835d352e1c 100644
> > > --- a/drivers/mtd/nand/mxc_nand.c
> > > +++ b/drivers/mtd/nand/mxc_nand.c
> > > @@ -807,32 +807,49 @@ static void mxc_nand_select_chip_v2(struct mtd_info *mtd, int chip)
> > > }
> > >
> > > /*
> > > - * Function to transfer data to/from spare area.
> > > + * The controller splits a page into data chunks of 512 bytes + partial oob.
> > > + * There are writesize / 512 such chunks, the size of the partial oob parts is
> > > + * oobsize / #chunks rounded down to a multiple of 2. The last oob chunk then
> > > + * contains additionally the byte lost by rounding (if any).
> > > + * This function handles the needed shuffling between host->data_buf (which
> > > + * holds a page in natural order, i.e. writesize bytes data + oobsize bytes
> > > + * spare) and the NFC buffer.
> > > */
> > > static void copy_spare(struct mtd_info *mtd, bool bfrom)
> > > {
> > > struct nand_chip *this = mtd->priv;
> > > struct mxc_nand_host *host = this->priv;
> > > u16 i, j;
> > > - u16 n = mtd->writesize >> 9;
> > > +
> > > + u16 num_chunks = mtd->writesize / 512;
> > > +
> > > u8 *d = host->data_buf + mtd->writesize;
> > > u8 __iomem *s = host->spare0;
> > > - u16 t = host->devtype_data->spare_len;
> > > + u16 sparebuf_size = host->devtype_data->spare_len;
> > >
> > > - j = (mtd->oobsize / n >> 1) << 1;
> > > + /* size of oob chunk for all but possibly the last one */
> > > + oob_chunk_size = (mtd->oobsize / num_chunks >> 1) << 1;
> > >
> > > if (bfrom) {
> > > - for (i = 0; i < n - 1; i++)
> > > - memcpy32_fromio(d + i * j, s + i * t, j);
> > > + for (i = 0; i < num_chunks - 1; i++)
> > > + memcpy32_fromio(d + i * oob_chunk_size,
> > > + s + i * sparebuf_size,
> > > + oob_chunk_size);
> > >
> > > /* the last section */
> > > - memcpy32_fromio(d + i * j, s + i * t, mtd->oobsize - i * j);
> > > + memcpy32_fromio(d + i * oob_chunk_size,
> > > + s + i * sparebuf_size,
> > > + mtd->oobsize - i * oob_chunk_size);
> > > } else {
> > > - for (i = 0; i < n - 1; i++)
> > > - memcpy32_toio(&s[i * t], &d[i * j], j);
> > > + for (i = 0; i < num_chunks - 1; i++)
> > > + memcpy32_toio(&s[i * sparebuf_size],
> > > + &d[i * oob_chunk_size],
> > > + oob_chunk_size);
> > >
> > > /* the last section */
> > > - memcpy32_toio(&s[i * t], &d[i * j], mtd->oobsize - i * j);
> > > + memcpy32_toio(&s[oob_chunk_size * sparebuf_size],
> > > + &d[i * oob_chunk_size],
> > > + mtd->oobsize - i * oob_chunk_size);
> > > }
> > > }
> > >
> > > What is needed now on top of this (untested and noop) change is to use
> > > the oob size the controller assumes instead of the real one and somehow
> > > explain that to the mtd layer and maintainers :-)
> >
> > Can't we just limit oobsize to 128 or 218? Something like (on top of your
> > patch):
> >
> > diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
> > index cc0eb79a177c..ae63f06fe99e 100644
> > --- a/drivers/mtd/nand/mxc_nand.c
> > +++ b/drivers/mtd/nand/mxc_nand.c
> > @@ -819,7 +819,7 @@ static void copy_spare(struct mtd_info *mtd, bool bfrom)
> > {
> > struct nand_chip *this = mtd->priv;
> > struct mxc_nand_host *host = this->priv;
> > - u16 i, j;
> > + u16 i, oob_chunk_size, used_oobsize;
> >
> > u16 num_chunks = mtd->writesize / 512;
> >
> > @@ -828,7 +828,13 @@ static void copy_spare(struct mtd_info *mtd, bool bfrom)
> > u16 sparebuf_size = host->devtype_data->spare_len;
> >
> > /* size of oob chunk for all but possibly the last one */
> > - oob_chunk_size = (mtd->oobsize / num_chunks >> 1) << 1;
> > + if (mtd->oobsize >= 218)
> > + used_oobsize = 218;
> > + else if (mtd->oobsize >= 128)
> > + used_oobsize = 128;
> > + else
> > + used_oobsize = mtd->oobsize;
> > + oob_chunk_size = (used_oobsize / num_chunks >> 1) << 1;
> something like that, yes. I'd make that conditional on writesize=4k and
> the register setting that is actually used by the controler however.
Why? The 128/218 oob limit seems to apply to smaller pages as well, isn't it?
> Also you need to adapt the reading/setting of the last chunk to make use
> of used_oobsize instead of mtd->oobsize.
Right.
We also need a matching nand_ecclayout for 8 bit ecc.
baruch
--
http://baruch.siach.name/blog/ ~. .~ Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
- baruch at tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -
More information about the linux-mtd
mailing list