GPMI-NAND: Wrong ECC size in driver

[Huang Shijie]

Hi Marek:
> Hi,
>
> the gpmi-nand.c driver apparently has misconfigured ecc.size field:
>
> drivers/mtd/nand/gpmi-nand/gpmi-nand.c:
> ---------->8 ----------
> 1493         chip->ecc.mode          = NAND_ECC_HW;
> 1494         chip->ecc.size          = 1;
> 1495         chip->ecc.layout        =&gpmi_hw_ecclayout;
> ---------- 8<  ----------
>
> This boils down to misconfigured mtd->subpage_sft in:
>
> drivers/mtd/nand/nand_base.c:
> ---------->8 ----------
> 3434         /* Allow subpage writes up to ecc.steps. Not possible for MLC flash
> */
> 3435         if (!(chip->options&  NAND_NO_SUBPAGE_WRITE)&&
> 3436             !(chip->cellinfo&  NAND_CI_CELLTYPE_MSK)) {
> 3437                 switch (chip->ecc.steps) {
> 3438                 case 2:
> 3439                         mtd->subpage_sft = 1;
> 3440                         break;
> 3441                 case 4:
> 3442                 case 8:
> 3443                 case 16:
> 3444                         mtd->subpage_sft = 2;
> 3445                         break;
> 3446                 }
> 3447         }
> 3448         chip->subpagesize = mtd->writesize>>  mtd->subpage_sft;
> ---------- 8<  ----------
>
> The mtd->subpage_sft is accidentally 0 by default. Therefore, the subpage size
> is mtd->writesize>>  0. Therefore the subpage size reported to UBI formating
> tools is the size of whole page, which works. Now, if I correct the problem by
> setting ecc.size properly to 512 bytes, I get into trouble with UBI:
>
> 1) UBI formating tools are reported the driver CAN DO subpage writes
> 2) UBI formating tools are reported the subpage size is 512 bytes
>
The gpmi driver does not support the subpage read/write.
I will be happy if the driver works only by setting the 
NAND_NO_SUBPAGE_WRITE, without setting the ecc.size.

Best Regards
Huang Shijie
> and this happens even though the NAND_NO_SUBPAGE_WRITE option is set by the
> driver. This is because:
>
> drivers/mtd/nand/nand_base.c:
> ---------->8 ----------
> 3072         /* Get chip options, preserve non chip based options */
> 3073         chip->options&= ~NAND_CHIPOPTIONS_MSK;
> 3074         chip->options |= type->options&  NAND_CHIPOPTIONS_MSK;
> ---------- 8<  ----------
>
> which effectively masks that bit away. So, how are we going to fix it?
>
> Cheers!
>
> Marek
>