From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from top.free-electrons.com ([176.31.233.9] helo=mail.free-electrons.com) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1VmN3p-0006qQ-HM for linux-mtd@lists.infradead.org; Fri, 29 Nov 2013 12:20:45 +0000 Date: Fri, 29 Nov 2013 09:20:19 -0300 From: Ezequiel Garcia To: Brian Norris Subject: Re: [PATCH v3] mtd/nand: don't use {read,write}_buf for 8-bit transfers Message-ID: <20131129122018.GB2815@localhost> References: <1365164021.28127.109.camel@i7.infradead.org> <1385500515-5376-1-git-send-email-u.kleine-koenig@pengutronix.de> <20131127073512.GB13929@norris.computersforpeace.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20131127073512.GB13929@norris.computersforpeace.net> Cc: Huang Shijie , linux-mtd@lists.infradead.org, Pekon Gupta , kernel@pengutronix.de, Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Brian, On Tue, Nov 26, 2013 at 11:35:12PM -0800, Brian Norris wrote: > + Pekon, Ezequiel > > Can one of you see how this patch works with your BeagleBones w/ x16 > NAND? > > Also, do you think on of you could take a look at killing the > nand_chip.read_word() callback, as Artem was originally requesting with > this patch? It only has one user (for bad block checking in > nand_block_bad(), which is currently only used when there is no BBT at > all), and it looks like it could be replaced with a call to > read_buf(mtd, buf, 2). > Sure, sounds doable. > Hi Uwe, > Uwe, If you're preparing a v4 to address Brian's feedback, then I'll see about testing it with 8/16-bit flashes on my AM335x. > On Tue, Nov 26, 2013 at 10:15:15PM +0100, Uwe Kleine-König wrote: > > According to the Open NAND Flash Interface Specification (ONFI) Revision > > 3.1 "Parameters are always transferred on the lower 8-bits of the data > > bus." for the Get Features and Set Features commands. > > > > So using read_buf and write_buf is wrong for 16-bit wide nand chips as > > they use I/O[15:0]. The Get Features command is easily fixed using 4 > > times the read_byte callback. For Set Features implement a new > > overwritable callback "write_byte". Still I expect the default to work > > just fine for all controllers and making it overwriteable was just done > > for symmetry. > > > > Signed-off-by: Uwe Kleine-König > > --- > > drivers/mtd/nand/nand_base.c | 61 +++++++++++++++++++++++++++++++++++++++++--- > > include/linux/mtd/nand.h | 3 +++ > > 2 files changed, 60 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c > > index bd39f7b..27d755b 100644 > > --- a/drivers/mtd/nand/nand_base.c > > +++ b/drivers/mtd/nand/nand_base.c > ... > > @@ -2706,7 +2751,7 @@ static int nand_block_markbad(struct mtd_info *mtd, loff_t ofs) > > } > > > > /** > > - * nand_onfi_set_features- [REPLACEABLE] set features for ONFI nand > > + * nand_onfi_set_features - [REPLACEABLE] set features for ONFI nand > > This change is unrelated. (Yes, the whitespace should be fixed, but > probably not in this patch.) > > > * @mtd: MTD device structure > > * @chip: nand chip info structure > > * @addr: feature address. > ... > > @@ -2731,7 +2779,7 @@ static int nand_onfi_set_features(struct mtd_info *mtd, struct nand_chip *chip, > > } > > > > /** > > - * nand_onfi_get_features- [REPLACEABLE] get features for ONFI nand > > + * nand_onfi_get_features - [REPLACEABLE] get features for ONFI nand > > Ditto. > > > * @mtd: MTD device structure > > * @chip: nand chip info structure > > * @addr: feature address. > ... > > @@ -2812,6 +2863,8 @@ static void nand_set_defaults(struct nand_chip *chip, int busw) > > chip->block_markbad = nand_default_block_markbad; > > if (!chip->write_buf || chip->write_buf == nand_write_buf) > > chip->write_buf = busw ? nand_write_buf16 : nand_write_buf; > > + if (!chip->write_byte) > > This check should be: > > if (!chip->write_byte || chip->write_byte == nand_write_byte) > > in order to match the rest of the functions, so they can be reset if the > buswidth is detected to be x16, and we re-call nand_set_defaults() > (e.g., when using NAND_BUSWIDTH_AUTO). See the comment: > > /* If called twice, pointers that depend on busw may need to be reset */ > > I know it's kind of ugly, but that's what we have for now. > > > + chip->write_byte = busw ? nand_write_byte16 : nand_write_byte; > > if (!chip->read_buf || chip->read_buf == nand_read_buf) > > chip->read_buf = busw ? nand_read_buf16 : nand_read_buf; > > if (!chip->scan_bbt) > > Brian -- Ezequiel García, Free Electrons Embedded Linux, Kernel and Android Engineering http://free-electrons.com