From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8AE98C2BB55 for ; Thu, 16 Apr 2020 15:07:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7108420774 for ; Thu, 16 Apr 2020 15:07:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2502065AbgDPPHI (ORCPT ); Thu, 16 Apr 2020 11:07:08 -0400 Received: from nbd.name ([46.4.11.11]:49192 "EHLO nbd.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2408793AbgDPNv6 (ORCPT ); Thu, 16 Apr 2020 09:51:58 -0400 Received: from [2a04:4540:1400:7b00:2d8:61ff:feed:60f5] by ds12 with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.89) (envelope-from ) id 1jP4vV-0004e0-L6; Thu, 16 Apr 2020 15:51:33 +0200 Subject: Re: [PATCH v1 2/2] mtd: rawnand: Add NAND controller support on Intel LGM SoC To: Arnd Bergmann , Boris Brezillon Cc: Andy Shevchenko , "Ramuthevar, Vadivel MuruganX" , Martin Blumenstingl , Anders Roxell , Andriy Shevchenko , Brendan Higgins , cheol.yong.kim@intel.com, devicetree , Linux Kernel Mailing List , "open list:MEMORY TECHNOLOGY..." , masonccyang@mxic.com.tw, Miquel Raynal , Piotr Sroka , qi-ming.wu@intel.com, Richard Weinberger , Rob Herring , Vignesh R , Songjun Wu , hua.ma@linux.intel.com, yixin.zhu@linux.intel.com, chuanhua.lei@linux.intel.com, Hauke Mehrtens References: <20200414022433.36622-3-vadivel.muruganx.ramuthevar@linux.intel.com> <20200415220533.733834-1-martin.blumenstingl@googlemail.com> <20200416113822.2ef326cb@collabora.com> <18568cf6-2955-472e-7b68-eb35e654a906@linux.intel.com> <20200416122619.2c481792@collabora.com> <20200416131725.51259573@collabora.com> <20200416135711.039ba85c@collabora.com> <20200416144036.3ce8432f@collabora.com> From: John Crispin Message-ID: <5cb0fe27-8b65-d777-b1c5-8dc47bda2d54@phrozen.org> Date: Thu, 16 Apr 2020 15:51:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16.04.20 15:20, Arnd Bergmann wrote: > On Thu, Apr 16, 2020 at 2:40 PM Boris Brezillon > wrote: >> On Thu, 16 Apr 2020 15:26:51 +0300 >> Andy Shevchenko wrote: >>> On Thu, Apr 16, 2020 at 3:03 PM Boris Brezillon >>> wrote: >>>> On Thu, 16 Apr 2020 19:38:03 +0800 >>>> Note that the NAND subsystem is full of unmaintained legacy drivers, so >>>> every time we see someone who could help us get rid or update one of >>>> them we have to take this opportunity. >>> >>> Don't we rather insist to have a MAINTAINERS record for new code to >>> avoid (or delay at least) the fate of the legacy drivers? >>> >> >> Well, that's what we do for new drivers, but the xway driver has been >> added in 2012 and the policy was not enforced at that time. BTW, that >> goes for most of the legacy drivers in have in the NAND subsystems >> (some of them even predate the git era). >> >> To be clear, I just checked and there's no official maintainer for this >> driver. Best option would be to Cc the original author and contributors >> who proposed functional changes to the code, as well as the MIPS >> maintainers (Xway is a MIPS platform). > > A lot of the pre-acquisition code for lantiq was contributed by Hauke > Mehrtens and John Crispin. There was an intermediate generation of > MIPS SoCs with patches posted for review by Intel in 2018 (presumably > by the same organizatiob), but those were never resubmitted after v2 > and never merged: > > https://lore.kernel.org/linux-mips/20180803030237.3366-1-songjun.wu@linux.intel.com/ > > Arnd > Hi, the legacy Mips SoC had a External Bus Unit (EBU), similar to an Intel/Hitachi style bus. It was used back then for lots of things, sometimes driving Leds via 74* latches, Arcadyan used it for external reset lines and very rarely was it used for nand. Looking at this series and comparing it with xway_nand.c we see that the init sequence is near identical. Best guess is that the mountain lion uses an internal block very similar to what the legacy mips silicon used just in a newer generation and the new proposed driver is more feature complete. If this is the case ideally the xway_nand.c is dropped and that silicon is made working with the newer driver. Chances are that we just need to add a "support less features" style flag. Unfortunately i no longer have the evalkit for the Mips SoCs. John