[U-Boot] [PATCH] nand_spl_simple: store ecc data on the stack

[Stefano Babic]

On 12/12/2011 01:08, Ilya Yanok wrote:
> Hi Stefano,
> 
> thanks for posting this. There is a couple of comments below.
> 
> On 11.12.2011 21:22, Stefano Babic wrote:
>> diff --git a/drivers/mtd/nand/nand_spl_simple.c b/drivers/mtd/nand/nand_spl_simple.c
>> index ed821f2..a3d1af0 100644
>> --- a/drivers/mtd/nand/nand_spl_simple.c
>> +++ b/drivers/mtd/nand/nand_spl_simple.c
>> @@ -145,9 +145,9 @@ static int nand_is_bad_block(int block)
>>  static int nand_read_page(int block, int page, uchar *dst)
>>  {
>>  	struct nand_chip *this = mtd.priv;
>> -	u_char *ecc_calc;
>> -	u_char *ecc_code;
>> -	u_char *oob_data;
>> +	u_char ecc_calc[CONFIG_SYS_NAND_ECCSTEPS * CONFIG_SYS_NAND_ECCBYTES];
>> +	u_char ecc_code[CONFIG_SYS_NAND_ECCTOTAL];
> 
> Doesn't ECCTOTAL always equal to ECCSTEPS * ECCBYTES?

I see. Then we can also remove CONFIG_SYS_NAND_ECCTOTAL from the
configuration files, because it is not useful. I will do in V2.

By grepping the code, the same issue is present in nand_spl/nand_boot.c,
too. This is part of the old spl code, I do not know if we have also to
fix this one. IMHO we can only fix nand_spl_simple.c, because the other
one will become obsolete and there is not probelms with current boards.

> 
>> +	u_char oob_data[CONFIG_SYS_NAND_OOBSIZE];
> 
> I think we can save a few bytes by placing ecc_code and oob_data into a
> union. We only need oob_data to get ecc_code...

Checking the real values I see that ECCTOTAL is small - 8 bytes on the
TI we are currently testing, and it has not a big value on other
architectures. So I think we can avoid the union, also because this can
generate overlapping when the oob data is copied: I mean in case
nand_ecc_pos[i] is smaller as CONFIG_SYS_NAND_ECCTOTAL at:

 for (i = 0; i < CONFIG_SYS_NAND_ECCTOTAL; i++)
                ecc_code[i] = oob_data[nand_ecc_pos[i]];



Regards,
Stefano

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