From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758987AbcAUI4f (ORCPT ); Thu, 21 Jan 2016 03:56:35 -0500 Received: from down.free-electrons.com ([37.187.137.238]:55647 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751096AbcAUI4c convert rfc822-to-8bit (ORCPT ); Thu, 21 Jan 2016 03:56:32 -0500 Date: Thu, 21 Jan 2016 09:56:30 +0100 From: Boris Brezillon To: "Bean Huo =?UTF-8?B?6ZyN5paM5paM?= (beanhuo)" Cc: Adam Somerville , 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: <20160121095630.4df558b3@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 Hi Bean, On Thu, 21 Jan 2016 01:06:48 +0000 Bean Huo 霍斌斌 (beanhuo) wrote: > Hi, Adam and Boris > > For Micron MT25Q ,MT25T and MT35Q, they does not exist this action even they are > Multi-die devices. So when the last byte of the die selected is read, the next byte output > is the first byte of next die(not the same die). > You can check this by extended address register chapter in our datasheet, there are detail > Information. I never said you were wrong ;), I just asked if it was relevant to differentiate the two cases. IOW, would the implementation proposed by Adam work correctly on all chips? And what is the real performance penalty for MT25Q ,MT25T and MT35Q if we decide to split the read command in several reads to handle this cross die case? Best Regards, Boris -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com