From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Agner Subject: Re: [PATCH v12 2/5] mtd: nand: vf610_nfc: add hardware BCH-ECC support Date: Wed, 07 Oct 2015 16:34:30 -0700 Message-ID: <0291312bcff1d7a22f7cdee69848dfcb@agner.ch> References: <1441242397-870-1-git-send-email-stefan@agner.ch> <1441242397-870-3-git-send-email-stefan@agner.ch> <20150929205727.GP31505@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150929205727.GP31505@google.com> Sender: linux-kernel-owner@vger.kernel.org To: Brian Norris Cc: dwmw2@infradead.org, sebastian@breakpoint.cc, robh+dt@kernel.org, pawel.moll@arm.com, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, shawn.guo@linaro.org, kernel@pengutronix.de, boris.brezillon@free-electrons.com, marb@ixxat.de, aaron@tastycactus.com, bpringlemeir@gmail.com, linux-mtd@lists.infradead.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, albert.aribaud@3adev.fr, klimov.linux@gmail.com, Bill Pringlemeir List-Id: devicetree@vger.kernel.org Hi Brian, On 2015-09-29 13:57, Brian Norris wrote: > Pushed this patch to l2-mtd.git, as it looks pretty much good. Although, > I'd like raw read support... > > On Wed, Sep 02, 2015 at 06:06:34PM -0700, Stefan Agner wrote: >> This adds hardware ECC support using the BCH encoder in the NFC IP. >> The ECC encoder supports up to 32-bit correction by using 60 error >> correction bytes. There is no sub-page ECC step, ECC is calculated >> always accross the whole page (up to 2k pages). >> >> Limitations: >> - HW ECC: Only 2K page with 64+ OOB. >> - HW ECC: Only 24 and 32-bit error correction implemented. >> >> Raw writes have been tested using the generic nand_write_page_raw >> implementation. However, raw reads are currently not possible >> because the controller need to know whether we are going to use >> the ECC mode already at NAND_CMD_READ0 command time. At this point >> we do not have the information whether it is a raw read or a >> regular read at driver level... > > Hmm, can you get this in ecc.read_page_raw()? Even just a read_page_raw implementation doesn't help. The controller requires the ECC to be configured at command issue time, and the driver issues the command in the cmdfunc callback. The function nand_do_read_ops calls cmdfunc before ecc.read_page_raw... I could just bail out in the NAND_CMD_READ0 case, and execute the command from within the ecc.read_page_raw callback function. A bit hacky, but that would work. For that case, it would be nicer if cmdfunc somehow provides the information that a raw read is requested, we would have that information in nand_do_read_ops. However, that would need an extension of the cmdfunc interface... Also, not sure how that should look like. -- Stefan