From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:55386 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727285AbeI0P3y (ORCPT ); Thu, 27 Sep 2018 11:29:54 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Steffen Trumtrar , Masahiro Yamada , Miquel Raynal , Boris Brezillon Subject: [PATCH 4.18 41/88] mtd: rawnand: denali: fix a race condition when DMA is kicked Date: Thu, 27 Sep 2018 11:03:22 +0200 Message-Id: <20180927090305.746943986@linuxfoundation.org> In-Reply-To: <20180927090300.631426620@linuxfoundation.org> References: <20180927090300.631426620@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Masahiro Yamada commit cf51e4b9c34407bf0c3d9b582b7837e047e1df47 upstream. 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") Cc: Reported-by: Steffen Trumtrar Signed-off-by: Masahiro Yamada Reviewed-by: Miquel Raynal Signed-off-by: Boris Brezillon Signed-off-by: Greg Kroah-Hartman --- drivers/mtd/nand/raw/denali.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/drivers/mtd/nand/raw/denali.c +++ b/drivers/mtd/nand/raw/denali.c @@ -604,6 +604,12 @@ static int denali_dma_xfer(struct denali } 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);