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

[Edgar E. Iglesias]

On Thu, Jan 07, 2010 at 03:19:15PM -0500, Jean-Hugues Deschenes wrote:
> > 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>/
> > >/ > +    unsigned int offset;/

...

> > >/ 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.

Hi,

I forgot about this one.. It's in one of my trees, I'll try to
find it & repost and see if there is more feedback.

My main concern was that I only had linux guests to test with.

Cheers