From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752485AbeDTUBm (ORCPT <rfc822;w@1wt.eu>);
        Fri, 20 Apr 2018 16:01:42 -0400
Received: from mail.bootlin.com ([62.4.15.54]:50430 "EHLO mail.bootlin.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751930AbeDTUBh (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 20 Apr 2018 16:01:37 -0400
Date: Fri, 20 Apr 2018 22:01:34 +0200
From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Ladislav Michl <ladis@linux-mips.org>
Cc: linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
        Boris Brezillon <boris.brezillon@free-electrons.com>,
        Peter Ujfalusi <peter.ujfalusi@ti.com>, Roger Quadros <rogerq@ti.com>,
        Aaro Koskinen <aaro.koskinen@iki.fi>, Tony Lindgren <tony@atomide.com>,
        "H. Nikolaus Schaller" <hns@goldelico.com>,
        Andreas Kemnade <andreas@kemnade.info>
Subject: Re: [PATCH v2] mtd: onenand: omap2: Disable DMA for HIGHMEM buffers
Message-ID: <20180420220134.3021860f@bbrezillon>
In-Reply-To: <20180416065256.GA24455@lenoch>
References: <20180416065256.GA24455@lenoch>
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
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi Ladislav,

On Mon, 16 Apr 2018 08:52:59 +0200
Ladislav Michl <ladis@linux-mips.org> wrote:

> dma_map_single doesn't get the proper DMA address for vmalloced area,

That's not true, it returns the right DMA (physical) address, it's just
that:

1/ the memory location is not necessarily physically contiguous
2/ in case your arch is VIVT ot VIPT, there may be several entries in
   the cache pointing to the same physical location, and the cache
   maintenance operations done by dma_map_single() will only operate on
   one of these entries.

> so disable DMA in this case.
> 

The fix looks good though. Can you rephrase your commit message to make
it clearer.

Thanks,

Boris