[U-Boot] Fix fsl_elbc_nand driver

[Andrei Yakimov]

For now lets stick with 1536 in u-boot.
I will send a patch.
At least it will not loosing flash over time
as nand ages.

I understand what you wish, and will take a look
on it inside fresh new kernel. I found one more driver  -
marvel looks like have same problem.
I will check how NAND_CMD_RNDOUT is working.
Perhaps we do not need extra read_param(),
and use only NAND_CMD_RNDOUT to get next
block inside page loop.

Andrei

On Wed, 2015-05-20 at 21:27 -0500, Scott Wood wrote:
> On Wed, 2015-05-20 at 18:55 -0700, Andrei Yakimov wrote:
> > On Wed, 2015-05-20 at 20:37 -0500, Scott Wood wrote:
> > > On Wed, 2015-05-20 at 18:27 -0700, Andrei Yakimov wrote:
> > > > For elbc and imx due to we reading all at once, it can not be stateless,
> > > > we need to read more and more each time
> > > 
> > > Why do we need to?  Why can't we read all three copies at once?
> > > 
> > > > reissuing command or relay on different way to ID chip - and this make
> > > > it pointless if it can not be done universally.
> > > 
> > > Or, we can reissue the command.  I don't see any big problem either way.
> > > This is not performance critical.
> > lets say  1 time you read 256 ( or 512) it go bad, next time you read
> > 512 (or 1024) next time you read 768 ( or 1536).
> 
> I was thinking read_param() would take the offset as a parameter and use
> NAND_CMD_RNDOUT to skip ahead -- but that would change the default flow
> which I'd rather avoid.  Another option is that read_param() just sets
> up the read for the specified number of bytes, but the caller still uses
> read_byte() to extract the data.  This way the code could specify
> sizeof(struct)*3 as the size up front without needing three separate
> buffers.
> 
> Note that whatever gets done should first be accepted in Linux, rather
> than being a local U-Boot change.  If you want a short-term fix, just
> stick 1536 in the eLBC driver.
> 
> > Upper layer can maintain it.
> > Roughly like this:
> > 
> > Was:
> > 	chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
> > 	for (i = 0; i < 3; i++) {
> > 		chip->read_buf(mtd, (uint8_t *)p, sizeof(*p));
> 
> You're looking at old code.  It uses read_byte() now.
> 
> > 		if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) ==
> > 						le16_to_cpu(p->crc)) {
> > 			break;
> > 		}
> > 	}
> > 	if (i == 3)
> > 		return 0;
> > 
> > new:
> > 	int read_size, offset;
> > 	read_size = 256;
> > 	offset =0;
> > 	if(!chip->read_param)
> > 		chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
> 
> I don't want "if (chip->read_param)" all over the place; there should be
> a default read_param() that does what the existing code does.
> 
> > 	for (i = 0; i < 3; i++) {
> > 		if(chip->read_param) chip->read_param( 0, read_size);
> > 		chip->read_buf(mtd, (uint8_t *)p + offest, sizeof(*p));
> 
> This isn't going to read the second or third copy; it's going to read
> the first copy and write beyond the end of your buffer.
> 
> -Scott
> 
>