2nd problem with read_subpage() ?
Artem Bityutskiy
dedekind at infradead.org
Tue Jul 29 05:45:07 EDT 2008
On Tue, 2008-07-29 at 12:30 +0300, Artem Bityutskiy wrote:
> On Tue, 2008-07-29 at 09:53 +0300, Artem Bityutskiy wrote:
> > Glance at nand_do_read_ops():
> >
> >
> > if (likely(sndcmd)) {
> > chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
> > sndcmd = 0;
> > }
>
> Alexey,
>
> my investigation showed that this "random output" command is not
> supported by all flashes. ST-micro NANDs seems to support it
> (I checked 2 manuals), while Sumsung NANDs do not (checked manual
> for K9XXG08UXA). This means your implementation will break many
> systems and should be either fixed or reverted.
I tried to implement this command in nandsim and test it with your
patch and found that there is something wring with how you use it.
What I do is dd if=/dev/mtd0 of=file bs=512 count=1 - just read one
sub-page. And in nandsim I see the following:
1. NAND_CMD_READ0 command, - read from eraseblock 0, column 0. This is
fine and seems to be called from nand_do_read_ops():
if (likely(sndcmd)) {
chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
sndcmd = 0;
}
2. Then NAND_CMD_RNDREAD command is issued with column address
0x828, which is completely weird. It is called from nand_read_subpage():
...
if (eccpos[(start_step + num_steps) * chip->ecc.bytes] & (busw - 1))
aligned_len++;
chip->cmdfunc(mtd, NAND_CMD_RNDOUT, mtd->writesize + aligned_pos, -1);
chip->read_buf(mtd, &chip->oob_poi[aligned_pos], aligned_len);
....
I do not understand what is going on.
--
Best regards,
Artem Bityutskiy (Битюцкий Артём)
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