Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936214AbdIZGoH (ORCPT ); Tue, 26 Sep 2017 02:44:07 -0400 Received: from mail.free-electrons.com ([62.4.15.54]:40904 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935374AbdIZGoD (ORCPT ); Tue, 26 Sep 2017 02:44:03 -0400 Date: Tue, 26 Sep 2017 08:43:56 +0200 From: Boris Brezillon To: Masahiro Yamada Cc: linux-mtd@lists.infradead.org, Cyrille Pitchen , linux-kernel@vger.kernel.org, Marek Vasut , Brian Norris , Richard Weinberger , David Woodhouse Subject: Re: [PATCH] mtd: nand: wait for tWHR after NAND_CMD_STATUS / NAND_CMD_READID Message-ID: <20170926084356.553867a1@bbrezillon> In-Reply-To: <1506397164-3648-1-git-send-email-yamada.masahiro@socionext.com> References: <1506397164-3648-1-git-send-email-yamada.masahiro@socionext.com> X-Mailer: Claws Mail 3.14.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1810 Lines: 57 On Tue, 26 Sep 2017 12:39:24 +0900 Masahiro Yamada wrote: > Read Status and Read ID require tWHR before reading the first data. > Insert a very short wait to make sure to meet the spec. > > I have not seen any problem report for now, but nand_command() and > nand_command_lP() are generic hooks, so it makes sense to implement > fail-safe code here. > > Signed-off-by: Masahiro Yamada > --- > > drivers/mtd/nand/nand_base.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c > index b1cf32c..55c0ba5 100644 > --- a/drivers/mtd/nand/nand_base.c > +++ b/drivers/mtd/nand/nand_base.c > @@ -742,9 +742,12 @@ static void nand_command(struct mtd_info *mtd, unsigned int command, > case NAND_CMD_ERASE1: > case NAND_CMD_ERASE2: > case NAND_CMD_SEQIN: > + case NAND_CMD_SET_FEATURES: > + return; > + > case NAND_CMD_STATUS: > case NAND_CMD_READID: > - case NAND_CMD_SET_FEATURES: > + ndelay(200); /* tWHR */ > return; > > case NAND_CMD_RESET: > @@ -871,9 +874,12 @@ static void nand_command_lp(struct mtd_info *mtd, unsigned int command, > case NAND_CMD_ERASE1: > case NAND_CMD_ERASE2: > case NAND_CMD_SEQIN: > + case NAND_CMD_SET_FEATURES: > + return; > + > case NAND_CMD_STATUS: > case NAND_CMD_READID: > - case NAND_CMD_SET_FEATURES: > + ndelay(200); /* tWHR */ Can you do something like nand_ccs_delay() [1] instead of unconditionally adding this 200ns delay here? I'm not worried about the overhead introduced by this ndelay(), but I don't want to risk introducing a regression. > return; > > case NAND_CMD_RNDIN: [1]http://elixir.free-electrons.com/linux/v4.14-rc2/source/drivers/mtd/nand/nand_base.c#L793