Re: [PATCH RESEND] mtd: nand: allow NAND_NO_SUBPAGE_WRITE to be set from driver

[Marek Vasut <marex@denx.de>]

Dear Matthieu CASTET,

> Hi Marek,
> 
> Marek Vasut a écrit :
> > Dear Matthieu CASTET,
> > 
> >> Hi,
> >> 
> >> for ONFI flash (like this micron one) the information should be
> >> extracted form the ONFI table (programs_per_page IIRC)
> >> 
> >> This should be better than relying on the SOC driver for setting this
> >> flags.
> >> 
> >> Does the gpmi driver set this flag because it do not support partial
> >> write ?
> > 
> > Yes
> > 
> >> In this case why it doesn't set  chip->ecc.steps to 1 ?
> > 
> > Can you elabore how exactly will that help please?
> 
> If you look at the nand_base.c, you will see that mtd->subpage_sft = 0 if
> NAND_NO_SUBPAGE_WRITE flags is set or chip->ecc.steps == 1 [1].

Ok, this is what I saw coming ... this is yet another hole in the design and I 
see only undefined behavior. So if default: branch started returning an error, 
this whole code will break again.


> [1]
>     /* Allow subpage writes up to ecc.steps. Not possible for MLC flash */
>     if (!(chip->options & NAND_NO_SUBPAGE_WRITE) &&
>         !(chip->cellinfo & NAND_CI_CELLTYPE_MSK)) {
>         switch (chip->ecc.steps) {
>         case 2:
>             mtd->subpage_sft = 1;
>             break;
>         case 4:
>         case 8:
>         case 16:
>             mtd->subpage_sft = 2;
>             break;
>         }
>     }
>     chip->subpagesize = mtd->writesize >> mtd->subpage_sft;

Best regards,
Marek Vasut