From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47694ECE560 for ; Mon, 17 Sep 2018 12:32:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E5FB7214D5 for ; Mon, 17 Sep 2018 12:32:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E5FB7214D5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728465AbeIQSAE (ORCPT ); Mon, 17 Sep 2018 14:00:04 -0400 Received: from mail.bootlin.com ([62.4.15.54]:37498 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728134AbeIQSAE (ORCPT ); Mon, 17 Sep 2018 14:00:04 -0400 Received: by mail.bootlin.com (Postfix, from userid 110) id D0CD620795; Mon, 17 Sep 2018 14:32:54 +0200 (CEST) Received: from bbrezillon (AAubervilliers-681-1-99-10.w90-88.abo.wanadoo.fr [90.88.4.10]) by mail.bootlin.com (Postfix) with ESMTPSA id 87CEE206A7; Mon, 17 Sep 2018 14:32:44 +0200 (CEST) Date: Mon, 17 Sep 2018 14:32:44 +0200 From: Boris Brezillon To: Masahiro Yamada Cc: linux-mtd@lists.infradead.org, Miquel Raynal , Steffen Trumtrar , Marek Vasut , Richard Weinberger , linux-kernel@vger.kernel.org, Brian Norris , David Woodhouse Subject: Re: [PATCH] mtd: rawnand: denali: fix a race condition when DMA is kicked Message-ID: <20180917143244.2e55fbac@bbrezillon> In-Reply-To: <1536818329-11068-1-git-send-email-yamada.masahiro@socionext.com> References: <1536818329-11068-1-git-send-email-yamada.masahiro@socionext.com> X-Mailer: Claws Mail 3.15.0-dirty (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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 13 Sep 2018 14:58:49 +0900 Masahiro Yamada wrote: > I thought the read-back of the DMA_ENABLE register was unnecessary > (at least it is working on my boards), then deleted it in commit > 586a2c52909d ("mtd: nand: denali: squash denali_enable_dma() helper > into caller"). Sorry, I was wrong - it caused a timing issue on > Cyclone5 SoCFPGAs. > > Revive the register read-back, commenting why this is necessary. > > Fixes: 586a2c52909d ("mtd: nand: denali: squash denali_enable_dma() helper into caller") > Reported-by: Steffen Trumtrar > Signed-off-by: Masahiro Yamada Queued to master. Thanks, Boris > --- > > drivers/mtd/nand/raw/denali.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/mtd/nand/raw/denali.c b/drivers/mtd/nand/raw/denali.c > index 67b2065..b864b93 100644 > --- a/drivers/mtd/nand/raw/denali.c > +++ b/drivers/mtd/nand/raw/denali.c > @@ -596,6 +596,12 @@ static int denali_dma_xfer(struct denali_nand_info *denali, void *buf, > } > > iowrite32(DMA_ENABLE__FLAG, denali->reg + DMA_ENABLE); > + /* > + * The ->setup_dma() hook kicks DMA by using the data/command > + * interface, which belongs to a different AXI port from the > + * register interface. Read back the register to avoid a race. > + */ > + ioread32(denali->reg + DMA_ENABLE); > > denali_reset_irq(denali); > denali->setup_dma(denali, dma_addr, page, write);