omap-l138: ECC generation latency of emifa

Hi Massimo,

I've checked the data sheet and TRM of the OMAPL138 but found nothing for ECC latency.
And I have tried to find the latency in linux OS by adding printks in between ECC calculation function.

For 1bit ECC, I got 4.87ms latency.
For 4bit ECC, I got 4.99ms latency.

I've modified the following source file and line.

linux/drivers/mtd/nand/davinci_nand.c

For 1bit ECC,

/*
* Read hardware ECC value and pack into three bytes
*/
static int nand_davinci_calculate_1bit(struct mtd_info *mtd,
const u_char *dat, u_char *ecc_code)
{
unsigned int ecc_val = nand_davinci_readecc_1bit(mtd);
unsigned int ecc24 = (ecc_val & 0x0fff) | ((ecc_val & 0x0fff0000) >> 4);

printk("NAND 1bit ECC probe start\n");

/* invert so that erased block ecc is correct */
ecc24 = ~ecc24;
ecc_code[0] = (u_char)(ecc24);
ecc_code[1] = (u_char)(ecc24 >> 8);
ecc_code[2] = (u_char)(ecc24 >> 16);

printk("NAND 1bit ECC probe end\n");

return 0;
}

Then I took between both probe prints and got the aforementioned values.

Please note that I've enabled "showing timing information with printks" in kernel through "make menuconfig"