[U-Boot] [PATCH v3 2/4] sunxi: nand: Add basic sunxi NAND driver for SPL with DMA support

[Michal Suchanek]

On 31 July 2015 at 11:24, Boris Brezillon
<boris.brezillon at free-electrons.com> wrote:
> Hi Hans,
>
> On Fri, 31 Jul 2015 10:36:43 +0200
> Hans de Goede <hdegoede at redhat.com> wrote:
>
>> Hi,
>>
>> On 31-07-15 02:47, Scott Wood wrote:
>> > On Thu, 2015-07-23 at 14:33 +0200, Piotr Zierhoffer wrote:
>> >> +int nand_spl_load_image(uint32_t offs, unsigned int size, void *dest)
>> >> +{
>> >> +     void *current_dest;
>> >> +     uint32_t count;
>> >> +     uint32_t current_count;
>> >> +     uint32_t ecc_errors = 0;
>> >> +
>> >> +     memset(dest, 0x0, size); /* clean destination memory */
>> >> +     for (current_dest = dest;
>> >> +                     current_dest < (dest + size);
>> >> +                     current_dest += CONFIG_NAND_SUNXI_SPL_ECC_PAGE_SIZE) {
>> >> +             nand_read_page(offs, offs
>> >> +                             < CONFIG_NAND_SUNXI_SPL_SYNDROME_PARTITIONS_END,
>> >> +                            &ecc_errors);
>> >> +             count = current_dest - dest;
>> >> +
>> >> +             if (size - count > CONFIG_NAND_SUNXI_SPL_ECC_PAGE_SIZE)
>> >> +                     current_count = CONFIG_NAND_SUNXI_SPL_ECC_PAGE_SIZE;
>> >> +             else
>> >> +                     current_count = size - count;
>> >> +
>> >> +             memcpy(current_dest,
>> >> +                    temp_buf,
>> >> +                    current_count);
>> >> +             offs += CONFIG_NAND_SUNXI_SPL_ECC_PAGE_SIZE;
>> >> +     }
>> >> +     return ecc_errors ? -1 : 0;
>> >> +}
>> >
>> > No bad block marker handling?
>>
>> The bootrom does not use bad block marker handling (and allwinner's
>> own FTL does neither for the non boot area, the actually mess up
>> things by writing metadata which looks like classic bad block
>> markers).
>
> Hm, checking for bad block markers (and skipping bad blocks) is always a
> good thing, even if it does not by itself guarantee that the data
> stored in there are not corrupted.

Not on Allwinner hardware. Allwinner tools write data to the nand
which looks like bad block markers so skipping blocks which appear
marked as bad will inevitably skip valid blocks on many (most ?)
Allwinner devices.

Only in the case you soldered a new nand chip yourself and never used
Allwinner tools with it will the bad block markers remain valid. This
is overall very unlikely so it should not be something SPL handles.

If you build custom devices and write devicetree for them then adding
an option there might be worthwhile.

Thanks

Michal