On Sun, Nov 02, 2008 at 12:31:53PM +0000, Ben Dooks wrote:
> On Sat, Nov 01, 2008 at 07:50:54PM -0200, Werner Almesberger wrote:
> > Ben Dooks wrote:
> > > My only comment would be
> > > that a slightly better solution would be to do:
> >
> > Oh, that's much better, thanks ! I hadn't realized at first that
> > once could read the FIFO one byte at a time.
> >
> > The revised patch is below.
> >
> > - Werner
> >
> > ---------------------------------- cut here
> > -----------------------------------
> >
> > fix-s3c-nand-read-bytes.patch
> >
> > With the introduction of optimized OOB reads in nand_read_subpage,
> > the length of the data requested may not be a multiple of four bytes.
> >
> > This caused a partial read on the 2440, leading to false ECC errors
> > and, worse, attempts to "correct" them.
> >
> > Note that there is a similar issue in s3c2440_nand_write_buf, which
> > doesn't seem to cause trouble yet.
> >
> > Signed-off-by: Werner Almesberger <[EMAIL PROTECTED]>
> >
> > ---
> >
> > Index: ktrack/drivers/mtd/nand/s3c2410.c
> > ===================================================================
> > --- ktrack.orig/drivers/mtd/nand/s3c2410.c 2008-11-01 19:25:11.000000000
> > -0200
> > +++ ktrack/drivers/mtd/nand/s3c2410.c 2008-11-01 19:38:07.000000000
> > -0200
> > @@ -530,7 +530,12 @@
> > static void s3c2440_nand_read_buf(struct mtd_info *mtd, u_char *buf, int
> > len)
> > {
> > struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
> > + u8 *ptr = buf + (len & ~3);
> > + int i;
> > +
> > readsl(info->regs + S3C2440_NFDATA, buf, len / 4);
> > + for (i = 0; i != (len & 3); i++)
> > + ptr[i] = readb(info->regs + S3C2440_NFDATA);
> > }
>
> actually, thinking about it, we can probably get better code by doing:
>
> /* mop up any non-word aligned length reads. */
> for (i = (len & ~3); i != len; i++)
> ptr[i] = readb(info->regs + S3C2440_NFDATA);
of course, that should have been buf[i].
> this removes the need for the extra ptr variable, the comment is also
> useful.
>
> > static void s3c2410_nand_write_buf(struct mtd_info *mtd, const u_char
> > *buf, int len)
> >
>
> --
> --
> Ben
>
> Q: What's a light-year?
> A: One-third less calories than a regular year.
>
>
--
--
Ben
Q: What's a light-year?
A: One-third less calories than a regular year.
