Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965467AbbD0WhG (ORCPT ); Mon, 27 Apr 2015 18:37:06 -0400 Received: from skprod2.natinst.com ([130.164.80.23]:56999 "EHLO ni.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965143AbbD0WhE (ORCPT ); Mon, 27 Apr 2015 18:37:04 -0400 Date: Mon, 27 Apr 2015 17:36:30 -0500 From: Ben Shelton To: Richard Weinberger Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, dwmw2@infradead.org, computersforpeace@gmail.com, punnaiah.choudary.kalluri@xilinx.com Subject: Re: [PATCH 1/3] mtd: nand: Add on-die ECC support Message-ID: <20150427223630.GA11721@bshelton-desktop> References: <1427292151-3835-1-git-send-email-richard@nod.at> <1427292151-3835-2-git-send-email-richard@nod.at> <20150427213558.GA22780@bshelton-desktop> <553EB5E4.3050309@nod.at> MIME-Version: 1.0 In-Reply-To: <553EB5E4.3050309@nod.at> User-Agent: Mutt/1.5.21 (2010-09-15) X-MIMETrack: Itemize by SMTP Server on US-AUS-MGWOut2/AUS/H/NIC(Release 8.5.3FP6|November 21, 2013) at 04/27/2015 05:36:37 PM, Serialize by Router on US-AUS-MGWOut2/AUS/H/NIC(Release 8.5.3FP6|November 21, 2013) at 04/27/2015 05:36:37 PM, Serialize complete at 04/27/2015 05:36:37 PM Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2015-04-28_01:,, signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3923 Lines: 81 On 04/28, Richard Weinberger wrote: > Am 27.04.2015 um 23:35 schrieb Ben Shelton: > > I tested this against the latest version of the PL353 NAND driver that Punnaiah > > has been working to upstream (copying her on this message). With a few changes > > to that driver, I got it most of the way through initialization with on-die ECC > > enabled, but it segfaults here with a null pointer dereference because the > > PL353 driver does not implement chip->cmd_ctrl. Instead, it implements a > > custom override of cmd->cmdfunc that does not call cmd_ctrl. Looking through > > the other in-tree NAND drivers, it looks like most of them do implement > > cmd_ctrl, but quite a few of them do not (e.g. au1550nd, denali, docg4). > > > > What do you think would be the best way to handle this? It seems like this gap > > could be bridged from either side -- either the PL353 driver could implement > > cmd_ctrl, at least as a stub version that provides the expected behavior in > > this case; or the on-die framework could break this out into a callback > > function with a default implementation that the driver could override to > > perform this behavior in the manner of its choosing. > > Oh, I thought every driver has to implement that function. ;-\ > But you're right there is a corner case. > > What we could do is just using chip->cmdfunc() with a custom NAND command. > i.e. chip->cmdfunc(mtd, NAND_CMD_READMODE, -1, -1); > > Gerhard Sittig tried to introduce such a command some time ago: > http://lists.infradead.org/pipermail/linux-mtd/2014-April/053115.html That sounds reasonable to me. That's similar to how we're checking the NAND status after reads in our current out-of-tree PL353 driver. We added the extra command: + /* + * READ0 command only, for checking read status. Note that the real command + * here is 0x00, but we can't differentiate between READ0 where we need to + * send a READSTART after the address bytes, or a READ0 by itself, after + * a read status command to check the on-die ECC status. The high bit is + * written into the unused end_cmd field, so we don't need to mask it off. + */ +#define NAND_CMD_READ0_ONLY 0x100 and then added it to the struct pl353_nand_command_format of the driver: static const struct pl353_nand_command_format pl353_nand_commands[] = { {NAND_CMD_READ0, NAND_CMD_READSTART, 5, PL353_NAND_CMD_PHASE}, + {NAND_CMD_READ0_ONLY, NAND_CMD_NONE, 0, NAND_CMD_NONE}, {NAND_CMD_RNDOUT, NAND_CMD_RNDOUTSTART, 2, PL353_NAND_CMD_PHASE}, {NAND_CMD_READID, NAND_CMD_NONE, 1, NAND_CMD_NONE}, {NAND_CMD_STATUS, NAND_CMD_NONE, 0, NAND_CMD_NONE}, > > Maybe Brian can bring some light into that too... > > > When I build this without CONFIG_MTD_NAND_ECC_ON_DIE enabled, I get the > > following warning here: > > > > In file included from drivers/mtd/nand/nand_base.c:46:0: > > include/linux/mtd/nand_ondie.h: In function 'nand_read_subpage_on_die': > > include/linux/mtd/nand_ondie.h:28:1: warning: no return statement in function returning non-void [-Wreturn-type] > > include/linux/mtd/nand_ondie.h: In function 'nand_read_page_on_die': > > include/linux/mtd/nand_ondie.h:34:1: warning: no return statement in function returning non-void [-Wreturn-type] > > > > Perhaps return an error code here, even though you'll never get past the BUG()? > > What gcc is this? > gcc 4.8 here does not warn, I thought it is smart enough that this function does never > return. Can it be that your .config has CONFIG_BUG=n? > Anyway, this functions clearly needs a return statement. :) gcc 4.7.2, and you are correct that I had CONFIG_BUG off. :) Thanks, Ben > > Thanks, > //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/