mtd_peb_write broken on dataflash

Ladislav Michl ladis at linux-mips.org
Fri Sep 21 02:46:36 PDT 2018


On Fri, Sep 21, 2018 at 09:11:11AM +0200, Sascha Hauer wrote:
> Hi Ladis,
> 
> On Thu, Sep 20, 2018 at 08:27:01PM +0200, Ladislav Michl wrote:
> > As mtd_peb_write checks for alignment, it fails writing to dataflash:
> > barebox$ state -s
> > ERROR: state: Failed to write PEB 0, -22
> > ERROR: state: Failed to write circular to 0 length 48, -22
> > WARNING: state: Failed to write state backend bucket, -22
> > ERROR: state: Failed to write PEB 1, -22
> > ERROR: state: Failed to write circular to 0 length 48, -22
> > WARNING: state: Failed to write state backend bucket, -22
> > ERROR: state: Failed to write PEB 2, -22
> > ERROR: state: Failed to write circular to 0 length 48, -22
> 
> How I read the code the length should be writesize aligned...

It is perfectly valid to write less to dataflash... But see bellow.

> > diff --git a/drivers/mtd/peb.c b/drivers/mtd/peb.c
> > index c35b63f2f..6035fbc45 100644
> > --- a/drivers/mtd/peb.c
> > +++ b/drivers/mtd/peb.c
> > @@ -376,7 +376,7 @@ int mtd_peb_write(struct mtd_info *mtd, const void *buf, int pnum, int offset,
> >  		return -EINVAL;
> >  	if (len <= 0)
> >  		return -EINVAL;
> > -	if (len % (mtd->writesize >> mtd->subpage_sft))
> > +	if (mtd->type != MTD_DATAFLASH && len % (mtd->writesize >> mtd->subpage_sft))
> 
> So how big is mtd->writesize here and is this value correct?

Yes, it is correct:
dataflash at 00: AT45DB041x (528 KBytes) pagesize 264 bytes (OTP)

> In state_storage_mtd_buckets_init() we have:
> 
>         if (circular)
>                 writesize = meminfo->writesize;
>         else
>                 writesize = meminfo->erasesize;
> 
> How big are meminfo->writesize and meminfo->erasesize here and
> which path is chosen?

writesize: 264
erasesize: 264
subpage_sft: 0
circular: true

But later we are trying to write 48 bytes:
dataflash0.barebox-state: write 48 bytes to PEB 0:0

	ladis



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