From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from down.free-electrons.com ([37.187.137.238] helo=mail.free-electrons.com) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1b7ImR-0003kL-Hh for linux-mtd@lists.infradead.org; Mon, 30 May 2016 08:42:36 +0000 Date: Mon, 30 May 2016 10:42:13 +0200 From: Boris Brezillon To: Kamal Dasu Cc: linux-mtd@lists.infradead.org, computersforpeace@gmail.com, f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com Subject: Re: [PATCH 1/2] mtd: brcmnand: Add check for erased page bitflips Message-ID: <20160530104213.79ff4a28@bbrezillon> In-Reply-To: <1461961285-24159-1-git-send-email-kdasu.kdev@gmail.com> References: <1461961285-24159-1-git-send-email-kdasu.kdev@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Kamal, On Fri, 29 Apr 2016 16:21:24 -0400 Kamal Dasu wrote: > Check for erased page bitflips in a page. And if well within > threshold return data as all 0xff. > > Signed-off-by: Kamal Dasu > --- > drivers/mtd/nand/brcmnand/brcmnand.c | 83 +++++++++++++++++++++++++++++++++--- > 1 file changed, 78 insertions(+), 5 deletions(-) > > diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c > index e052839..29a9abd 100644 > --- a/drivers/mtd/nand/brcmnand/brcmnand.c > +++ b/drivers/mtd/nand/brcmnand/brcmnand.c > @@ -1490,6 +1490,64 @@ static int brcmnand_read_by_pio(struct mtd_info *mtd, struct nand_chip *chip, > return ret; > } > > +/* > + * Check a page to see if it is erased (w/ bitflips) after an uncorrectable ECC > + * error > + * > + * Because the HW ECC signals an ECC error if an erase paged has even a single > + * bitflip, we must check each ECC error to see if it is actually an erased > + * page with bitflips, not a truly corrupted page. > + * > + * On a real error, return a negative error code (-EBADMSG for ECC error), and > + * buf will contain raw data. > + * Otherwise, fill buf with 0xff and return the maximum number of > + * bitflips-per-ECC-sector to the caller. > + * > + */ > +static int brcmstb_nand_verify_erased_page(struct mtd_info *mtd, > + struct nand_chip *chip, void *buf, u64 addr) > +{ > + int i, sas, oob_nbits, data_nbits; > + void *oob = chip->oob_poi; > + unsigned int max_bitflips = 0; > + int page = addr >> chip->page_shift; > + int ret; > + > + if (!buf) { > + buf = chip->buffers->databuf; > + /* Invalidate page cache */ > + chip->pagebuf = -1; > + } > + > + sas = mtd->oobsize / chip->ecc.steps; > + oob_nbits = sas << 3; > + data_nbits = chip->ecc.size << 3; > + > + /* read without ecc for verification */ > + chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page); > + ret = chip->ecc.read_page_raw(mtd, chip, buf, true, page); Do you really need to read the whole page in raw mode? Usually, only reading the OOB sections is enough. > + if (ret) > + return ret; > + > + for (i = 0; i < chip->ecc.steps; i++, oob += sas) { > + unsigned int bitflips = 0; > + > + bitflips += oob_nbits - bitmap_weight(oob, oob_nbits); > + bitflips += data_nbits - bitmap_weight(buf, data_nbits); > + > + buf += chip->ecc.size; > + addr += chip->ecc.size; You seem to duplicate nand_check_erased_ecc_chunk() here. Do you have a good reason for doing that? Regards, Boris -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com