From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933318AbcATMY4 (ORCPT ); Wed, 20 Jan 2016 07:24:56 -0500 Received: from down.free-electrons.com ([37.187.137.238]:36585 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933065AbcATMYp convert rfc822-to-8bit (ORCPT ); Wed, 20 Jan 2016 07:24:45 -0500 Date: Wed, 20 Jan 2016 13:24:33 +0100 From: Boris Brezillon To: Adam Somerville Cc: "Bean Huo =?UTF-8?B?6ZyN5paM5paM?= (beanhuo)" , David Woodhouse , Brian Norris , "linux-mtd@lists.infradead.org" , "zajec5@gmail.com" , "jteki@openedev.com" , "mika.westerberg@linux.intel.com" , "furquan@google.com" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC] spi-nor: fix cross die reads on Micron multi-die devices Message-ID: <20160120132433.3d201299@bbrezillon> In-Reply-To: References: X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.27; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Adam, Bean, On Wed, 20 Jan 2016 12:01:06 +0000 Adam Somerville wrote: > Hi, > > Thanks for looking at the this. > > I can rewrite so it only affects N25Q devices, I hoped a simpler > implementation would outweigh the small overhead incurred on non > affected devices. I tend to think the same way: not sure the performance penalty is worth the pain. Best Regards, Boris > > Do you know if there are any plans for MT25* based multi-die devices > and if they would have the same issue? > > Thanks, > > Adam > > On Wed, Jan 20, 2016 at 2:45 AM, Bean Huo 霍斌斌 (beanhuo) > wrote: > > Hi, Adam > > This is true, but this only exist in Micron 65nm spi nor N25Q. > > For our 45nm spi nor MT25Q , MT25TL and MT25Q, does exist this question. > > So I think, can you differentiate between these in your patch? > > > >> From: Adam Somerville > >> > >> So as far as I can see there is a bug in the spi-nor driver when issuing die > >> boundary crossing reads on Micron multi-die devices. > >> Micron N25Q512A, N25Q00AA and probably any other Micron multi-die > >> devices do not support a single read request that crosses a die boundary. > >> > >> The current behaviour is that the address on the device wraps back to the > >> start of the first die, with any data returned beyond the boundary being from > >> the start of the first die. > >> -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com