From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from guitar.tcltek.co.il ([192.115.133.116] helo=mx.tkos.co.il) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1YkU0p-0006Jj-IS for linux-mtd@lists.infradead.org; Tue, 21 Apr 2015 08:58:36 +0000 Date: Tue, 21 Apr 2015 11:58:08 +0300 From: Baruch Siach To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: i.MX25 NFC with 8 bit ecc strength Message-ID: <20150421085808.GL5428@tarshish> References: <20150420045614.GC5428@tarshish> <20150420073702.GA2552@pengutronix.de> <20150420091130.GD5428@tarshish> <20150420154818.GE2552@pengutronix.de> <20150421062428.GJ5428@tarshish> <20150421073936.GI2552@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20150421073936.GI2552@pengutronix.de> Cc: Shawn Guo , linux-mtd@lists.infradead.org, Sascha Hauer List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Uwe, On Tue, Apr 21, 2015 at 09:39:36AM +0200, Uwe Kleine-König wrote: > On Tue, Apr 21, 2015 at 09:24:28AM +0300, Baruch Siach wrote: > > On Mon, Apr 20, 2015 at 05:48:18PM +0200, Uwe Kleine-König wrote: > > > This is more or less expected. The "more" part is: Matching the hardware > > > description the (virtual) spare area is sorted into the spare area > > > buffers, so the first spare area is written to 0xbb001000, the 2nd to > > > 0xbb001040 etc. (See table 36-3 in the manual.) So probably it's the > > > driver who doesn't get the sorting right. > > > > OK. I see what you mean. The 28 bytes interval has noting to do with hardware. > > It comes from this line in copy_spare(): > > > > j = (mtd->oobsize / n >> 1) << 1; > > > > In my case oobsize = 224, and n = 8 (512 bytes steps), so j == 28. This means > > that we must generate nand_ecclayout at run time according to the actual > > oobsize. This is probably also true for the 4 bit ecc case. > I think you're only partly right here. The NFC only supports 128 or 218 > bytes spare area for 4k NAND flashes (initialized by BT_SPARE_SIZE). For > you chip the controller uses the 218 bytes setting, so 26 bytes are read > for the first 7 oob chunks each (last one: 36) As the driver assumes the > real oob size of 224 bytes you get that offset of 28 instead. > > So looking again on your hexdump: > > 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| > * > This is the data part, everything in order > > 00001000 ff ff ff ff ff ff ff 91 c4 45 be 32 45 6f 5d b1 |.........E.2Eo].| > 00001010 b1 b9 13 61 59 7d 42 58 eb ff ff ff ff ff ff ff |...aY}BX........| > Up to the 26th byte --------------------------^^ this is data coming > from the flash. The following two 0xff are just what happened to be > written in the NFC buffer. Starting with the four last 0xff in that line > we have real data again. > > 00001020 ff ff ff 91 c4 45 be 32 45 6f 5d b1 b1 b9 13 61 |.....E.2Eo]....a| > which makes the first ecc byte again the 8th of the oob chunk similar to > the one above. Thanks for your explanation. [...] > While understanding the problem I produced the following (untested) > patch: > > diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c > index dca63a70e783..fc835d352e1c 100644 > --- a/drivers/mtd/nand/mxc_nand.c > +++ b/drivers/mtd/nand/mxc_nand.c > @@ -807,32 +807,49 @@ static void mxc_nand_select_chip_v2(struct mtd_info *mtd, int chip) > } > > /* > - * Function to transfer data to/from spare area. > + * The controller splits a page into data chunks of 512 bytes + partial oob. > + * There are writesize / 512 such chunks, the size of the partial oob parts is > + * oobsize / #chunks rounded down to a multiple of 2. The last oob chunk then > + * contains additionally the byte lost by rounding (if any). > + * This function handles the needed shuffling between host->data_buf (which > + * holds a page in natural order, i.e. writesize bytes data + oobsize bytes > + * spare) and the NFC buffer. > */ > static void copy_spare(struct mtd_info *mtd, bool bfrom) > { > struct nand_chip *this = mtd->priv; > struct mxc_nand_host *host = this->priv; > u16 i, j; > - u16 n = mtd->writesize >> 9; > + > + u16 num_chunks = mtd->writesize / 512; > + > u8 *d = host->data_buf + mtd->writesize; > u8 __iomem *s = host->spare0; > - u16 t = host->devtype_data->spare_len; > + u16 sparebuf_size = host->devtype_data->spare_len; > > - j = (mtd->oobsize / n >> 1) << 1; > + /* size of oob chunk for all but possibly the last one */ > + oob_chunk_size = (mtd->oobsize / num_chunks >> 1) << 1; > > if (bfrom) { > - for (i = 0; i < n - 1; i++) > - memcpy32_fromio(d + i * j, s + i * t, j); > + for (i = 0; i < num_chunks - 1; i++) > + memcpy32_fromio(d + i * oob_chunk_size, > + s + i * sparebuf_size, > + oob_chunk_size); > > /* the last section */ > - memcpy32_fromio(d + i * j, s + i * t, mtd->oobsize - i * j); > + memcpy32_fromio(d + i * oob_chunk_size, > + s + i * sparebuf_size, > + mtd->oobsize - i * oob_chunk_size); > } else { > - for (i = 0; i < n - 1; i++) > - memcpy32_toio(&s[i * t], &d[i * j], j); > + for (i = 0; i < num_chunks - 1; i++) > + memcpy32_toio(&s[i * sparebuf_size], > + &d[i * oob_chunk_size], > + oob_chunk_size); > > /* the last section */ > - memcpy32_toio(&s[i * t], &d[i * j], mtd->oobsize - i * j); > + memcpy32_toio(&s[oob_chunk_size * sparebuf_size], > + &d[i * oob_chunk_size], > + mtd->oobsize - i * oob_chunk_size); > } > } > > What is needed now on top of this (untested and noop) change is to use > the oob size the controller assumes instead of the real one and somehow > explain that to the mtd layer and maintainers :-) Can't we just limit oobsize to 128 or 218? Something like (on top of your patch): diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c index cc0eb79a177c..ae63f06fe99e 100644 --- a/drivers/mtd/nand/mxc_nand.c +++ b/drivers/mtd/nand/mxc_nand.c @@ -819,7 +819,7 @@ static void copy_spare(struct mtd_info *mtd, bool bfrom) { struct nand_chip *this = mtd->priv; struct mxc_nand_host *host = this->priv; - u16 i, j; + u16 i, oob_chunk_size, used_oobsize; u16 num_chunks = mtd->writesize / 512; @@ -828,7 +828,13 @@ static void copy_spare(struct mtd_info *mtd, bool bfrom) u16 sparebuf_size = host->devtype_data->spare_len; /* size of oob chunk for all but possibly the last one */ - oob_chunk_size = (mtd->oobsize / num_chunks >> 1) << 1; + if (mtd->oobsize >= 218) + used_oobsize = 218; + else if (mtd->oobsize >= 128) + used_oobsize = 128; + else + used_oobsize = mtd->oobsize; + oob_chunk_size = (used_oobsize / num_chunks >> 1) << 1; if (bfrom) { for (i = 0; i < num_chunks - 1; i++) baruch -- http://baruch.siach.name/blog/ ~. .~ Tk Open Systems =}------------------------------------------------ooO--U--Ooo------------{= - baruch@tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -