Re: [Qemu-devel] [PATCH] NAND: Correct random data reads

[Jean-Hugues Deschenes <jean-hugues.deschenes@octasic.com>]

> On Mon, Dec 15, 2008 at 03:31:55AM +0100, andrzej zaborowski wrote:
> >/ 2008/12/12 Edgar E. Iglesias <address@hidden>:/
> >/ > I'm having problems with machine that uses a NAND_MFR_STMICRO 0xf1,/
> >/ > recent Linux versions cannot properly read from the flash./
> >/ >/
> >/ > Turns out that Linux MTD recently learned howto do randomly accessed reads/
> >/ > from NAND flashes. QEMU has problemns emulating these./
> >/ >/
> >/ > This patch fixes the problem for me but I've only tested on one flash/
> >/ > model and only with Linux. I'd appreciate help with testing more machines/
> >/ > with NANDs and ofcourse any comments people may have on the patch./
> >/ >/
> >/ > Thanks/
> >/ >/
> >/ > commit 68a19f4348b12f85bd5fbfd8cf7b19033e1fd784/
> >/ > Author: Edgar E. Iglesias <address@hidden>/
> >/ > Date:   Fri Dec 12 12:48:58 2008 +0100/
> >/ >/
> >/ >    NAND: Correct random data reads./
> >/ >/
> >/ >    Random reading depends on having the last row/page latched and not beeing/
> >/ >    clobbered between read and any following random reads./
> >/ >/
> >/ >    Also, s->iolen must be updated when loading the io/data register with /
> >/ > randomly/
> >/ >    accessed flash data./
> >/ >/
> >/ >    Signed-off-by: Edgar E. Iglesias <address@hidden>/
> >/ >/
> >/ > diff --git a/hw/nand.c b/hw/nand.c/
> >/ > index 7c9f0aa..a6f67c6 100644/
> >/ > --- a/hw/nand.c/
> >/ > +++ b/hw/nand.c/
> >/ > @@ -212,6 +212,7 @@ void nand_reset(struct nand_flash_s *s)/
> >/ >/
> >/ >  static void nand_command(struct nand_flash_s *s)/
> >/ >  {/
> >/ > +    unsigned int offset;/
> >/ >     switch (s->cmd) {/
> >/ >     case NAND_CMD_READ0:/
> >/ >         s->iolen = 0;/
> >/ > @@ -233,8 +234,12 @@ static void nand_command(struct nand_flash_s *s)/
> >/ >     case NAND_CMD_NOSERIALREAD2:/
> >/ >         if (!(nand_flash_ids[s->chip_id].options & NAND_SAMSUNG_LP))/
> >/ >             break;/
> >/ > -/
> >/ > -        s->blk_load(s, s->addr, s->addr & ((1 << s->addr_shift) - 1));/
> >/ > +        offset = s->addr & ((1 << s->addr_shift) - 1);/
> >/ > +        s->blk_load(s, s->addr, offset);/
> >/ > +        if (s->gnd)/
> >/ > +            s->iolen = (1 << s->page_shift) - offset;/
> >/ > +        else/
> >/ > +            s->iolen = (1 << s->page_shift) + (1 << s->oob_shift) - offset;/
> >/ >         break;/
> >/ >/
> >/ >     case NAND_CMD_RESET:/
> >/ > @@ -380,12 +385,15 @@ void nand_setio(struct nand_flash_s *s, uint8_t value)/
> >/ >/
> >/ >         if (s->cmd != NAND_CMD_RANDOMREAD2) {/
> >/ >             s->addrlen = 0;/
> >/ > -            s->addr = 0;/
> >/ >         }/
> >/ >     }/
> >/ >/
> >/ >     if (s->ale) {/
> >/ > -        s->addr |= value << (s->addrlen * 8);/
> >/ > +        unsigned int shift = s->addrlen * 8;/
> >/ > +        unsigned int mask = ~(0xff << shift);/
> >/ > +        unsigned int v = value << shift;/
> >/ > +/
> >/ > +        s->addr = (s->addr & mask) | v;/
> >/ >         s->addrlen ++;/
> >/ >/
> >/ >         if (s->addrlen == 1 && s->cmd == NAND_CMD_READID)/
> >/ > @@ -680,9 +688,6 @@ static void glue(nand_blk_load_, PAGE_SIZE)(struct /
> >/ > nand_flash_s *s,/
> >/ >                         offset, PAGE_SIZE + OOB_SIZE - offset);/
> >/ >         s->ioaddr = s->io;/
> >/ >     }/
> >/ > -/
> >/ > -    s->addr &= PAGE_SIZE - 1;/
> >/ > -    s->addr += PAGE_SIZE;/
> >/ /
> >/ Won't that break sequential reading?  I think the other modifications/
>
> I found specs for a flash with sequential page-crossing reads. My
> code does not handle that but neither does current svn AFAICT. The
> masking is wrong, we'll always end up at page 1.
>
> >/ should also be conditional on the command being RANDOMREAD./
> >/ /
> >/ BTW, do you happen to know what the difference is between RANDOMREAD2/
> >/ and NOSERIALREAD2?  I basically added those commands because various/
>
> AFAIK noserial reads are for preparing copyback writes. Random reads are
> for random access within the page register.
>
> I'll try to fix and test the page-crossing seqreads.
>
> Thanks alot for the comments.
Hi,

	I'm just wondering what is the status of this patch; It has definitely solved one of my problems, where a NAND flash controller I'm emulating sends random read commands to an emulated large page device.

jh