Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752808AbbGTJXq (ORCPT ); Mon, 20 Jul 2015 05:23:46 -0400 Received: from eusmtp01.atmel.com ([212.144.249.243]:42851 "EHLO eusmtp01.atmel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750825AbbGTJXo (ORCPT ); Mon, 20 Jul 2015 05:23:44 -0400 Message-ID: <55ACBE1B.6050507@atmel.com> Date: Mon, 20 Jul 2015 11:23:39 +0200 From: Cyrille Pitchen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Marek Vasut CC: , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH 4/7] Documentation: mtd: add a DT property to set the latency code of Spansion memory References: <398ca9f17bda638e05e97f258fb4e6d27ac828db.1437059658.git.cyrille.pitchen@atmel.com> <201507161944.20523.marex@denx.de> In-Reply-To: <201507161944.20523.marex@denx.de> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.161.30.18] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1792 Lines: 47 Hi Marek, Le 16/07/2015 19:44, Marek Vasut a ?crit : > On Thursday, July 16, 2015 at 05:27:51 PM, Cyrille Pitchen wrote: > > Hi! > >> Both the SPI controller and the NOR flash memory need to agree on the >> number of dummy cycles to use for Fast Read commands. For Spansion >> memories, this number of dummy cycles is not given directly but through a >> so called "latency code". >> The latency code can be found into the memory datasheet and depends on the >> SPI clock frequency, the Fast Read op code and the Single/Dual Data Rate >> mode. > > Shouldn't you be able to derive the latency code from the above information, > which you already know then ? Yes I agree with you; this could have been done adding static tables inside the driver instead of creating a new DT property dedicated to Spansion memories. When I wrote this patch, I had a close look at the s25fl512s datasheet but only overviewed few datasheets for other Spansion QSPI flash memories. So I don't know whether a single latency code table could be shared among all Spansion memories or many tables should be added to support different memory models. That's why I've chosen to add a dedicated DT property to support Spansion memories as it avoids to add tables to guess the proper latency code to be used. I thought it would be more flexible. Maybe I will remove the support of Spansion QSPI memories from this series for now. Their support can still be implemented later. Anyway, thanks for your review :) > > Best regards, > Marek Vasut > Best Regards, Cyrille -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/