[U-Boot] omap: Looking to dynamically setup ECC and nand settings during boot

[Gupta, Pekon]

Hi Jon,


>From: Jon Cormier [mailto:jcormier at criticallink.com] 

> We have a product based on the 335x that has several different models where the only difference is the nand part.  We would like to have a unified u-boot that can dynamically configure the nand's ECC, page size, block size, etc using a spi eeprom containing a model number.  Both the UBL and u-boot image are stored in nand. We already do this in the kernel.  Currently in the UBL all the nand information is setup in #defines during compile time which makes it hard to change at runtime.  I am unsure how to go about changing this.  Has anyone tried doing this dynamic setup?

(1) For NAND device parameters (like Block-size, Page-size, data-width)
These parameter are anyways dynamically determined by reading on chip
ONFI page during omap_board_init(). But that's only for u-boot (second-stage).
- For SPL these are still #defined based to keep the code-footprint small.


(2) For dynamically selection of ecc-scheme, you need to re-add
'nandecc' command which is kind of deprecated now. Though its
driver side support is still present in omap_gpmc.c.
- But again, this is not supported for SPL.
If everyone agrees, we should add this to main NAND framework
instead of cluttering individual board-files.
------------------------------------------------------------------
File: arch/arm/cpu/armv7/omap3/board.c

#if defined(CONFIG_NAND_OMAP_GPMC) & !defined(CONFIG_SPL_BUILD)
/******************************************************************************
 * OMAP3 specific command to switch between NAND HW and SW ecc
 *****************************************************************************/
static int do_switch_ecc(cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
{
	if (argc < 2 || argc > 3)
		goto usage;

	if (strncmp(argv[1], "hw", 2) == 0) {
		if (argc == 2) {
			omap_nand_switch_ecc(1, 1);
		} else {
			if (strncmp(argv[2], "hamming", 7) == 0)
				omap_nand_switch_ecc(1, 1);
			else if (strncmp(argv[2], "bch8", 4) == 0)
				omap_nand_switch_ecc(1, 8);
			else
				goto usage;
		}
	} else if (strncmp(argv[1], "sw", 2) == 0) {
		omap_nand_switch_ecc(0, 0);
	} else {
		goto usage;
	}

	return 0;

usage:
	printf ("Usage: nandecc %s\n", cmdtp->usage);
	return 1;
}

U_BOOT_CMD(
	nandecc, 3, 1,	do_switch_ecc,
	"switch OMAP3 NAND ECC calculation algorithm",
	"hw [hamming|bch8] - Switch between NAND hardware 1-bit hamming and"
	" 8-bit BCH\n"
	"                           ecc calculation (second parameter may"
	" be omitted).\n"
	"nandecc sw               - Switch to NAND software ecc algorithm."
);

#endif /* CONFIG_NAND_OMAP_GPMC & !CONFIG_SPL_BUILD */
------------------------------------------------------------------


(3) If you need to have generic SPL too, then you might need to try
NANDI2C boot-mode of AM335x. (please refer AM335x TRM).


> We are currently based off of the 2013.10 tag but will move forward if needed.
Yes, I would suggest to move to latest u-boot which has support
for BCH16 ecc-scheme, as higher ecc-scheme work better with newer
technology NAND and MLC NAND devices which are more prone
to bit-flips.


with regards, pekon

> -- 
> Jonathan Cormier
> CriticalLink