linux-kernel - RE: enhance ONFI table reliability/stable

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Date:	Thu, 19 Nov 2015 04:21:01 +0000
From:	Bean Huo 霍斌斌 (beanhuo) 
	<beanhuo@...ron.com>
To:	Brian Norris <computersforpeace@...il.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"Boris Brezillon" <boris.brezillon@...e-electrons.com>
Subject: RE: enhance ONFI table reliability/stable

> 
> Hi Bean,
> 
> I was sorting through old email and I found this.
> 
> On Tue, Jul 21, 2015 at 02:42:34PM +0000, Bean Huo 霍斌斌 (beanhuo)
> wrote:
> > Hi,
> >
> > Recently, I faced some case about ONFI table reliability, now it used CRC.
> > If there is bit flips in ONFI parameter pages, parameter backup page will be
> taken.
> > For latest linux,default read three copys.
> >
> > 	chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
> > 	for (i = 0; i < 3; i++) {
> > 		for (j = 0; j < sizeof(*p); j++)
> > 			((uint8_t *)p)[j] = chip->read_byte(mtd);
> > 		if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) ==
> > 				le16_to_cpu(p->crc)) {
> > 			break;
> > 		}
> > 	}
> >
> > However ,with technoogy improvement,for TLC and new generatin MLC,I
> > think, three copys of
> 
> Ha, "improvement" :)
> 
> > Parameter tables is not powerful enough.my question is that if there
> > is a good method to protect and corrent parameter page. For example,we
> > can use linux software BCH ecc. Any suggections and input be
> > welcomed,if you having any concerns about this,don't free tell me.
> 
> I recall this being brought up at my old job, and I all I can say is...
> (please pardon my censored language)


Yes , you ever told about this. I just follow.
Sorry for my rude following.
I only want to share my one suggestion about using software ECC to protect 
ONFI table that read from NAND. I want to hear every MTD expert 's valuable 
Feedback on this. if OK, I can do it. 

> ...that is complete and utter bulls***. An ONFI standard that can't guarantee
> "reliable enough" parameter pages is no standard at all.
> 
> To step back a bit: How would one expect to store and retrieve ECC parity
> data? ...on the NAND flash? But to do that, we have to know the geometry
> parameters of said NAND flash. How do we figure out the geometry? From the
> ONFI parameter pages! Nice Catch 22 you have there.
> 
> Please encourage your employer never to produce "ONFI-compliant" flash that
> are this bad.
> 
> Regards,
> Brian