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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 31-07-15 16:25, Michal Suchanek wrote:
> On 31 July 2015 at 11:24, Boris Brezillon
> <boris.brezillon@free-electrons.com> wrote:
>> Hi Hans,
>>
>> On Fri, 31 Jul 2015 10:36:43 +0200
>> Hans de Goede <hdegoede@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.

Right this has been my observation as well.

> 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.

Or if you've some device where the nand was not initialized from
the factory, I think some Olinuxino devices with nand fall into this
category.

I agree that is best to simply ignore bad block markers on sunxi
though, as they tend to lead to many false positives (think 60% of
the entire nand consisting of bad blocks in my experience)

Regards,

Hans