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=-10.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=ham 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 80F0BC4332D for ; Fri, 20 Mar 2020 17:12:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5482220739 for ; Fri, 20 Mar 2020 17:12:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727385AbgCTRMI convert rfc822-to-8bit (ORCPT ); Fri, 20 Mar 2020 13:12:08 -0400 Received: from relay9-d.mail.gandi.net ([217.70.183.199]:54637 "EHLO relay9-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726855AbgCTRMH (ORCPT ); Fri, 20 Mar 2020 13:12:07 -0400 X-Originating-IP: 91.224.148.103 Received: from xps13 (unknown [91.224.148.103]) (Authenticated sender: miquel.raynal@bootlin.com) by relay9-d.mail.gandi.net (Postfix) with ESMTPSA id 6BFE2FF802; Fri, 20 Mar 2020 17:12:00 +0000 (UTC) Date: Fri, 20 Mar 2020 18:11:59 +0100 From: Miquel Raynal To: Masahiro Yamada Cc: linux-mtd@lists.infradead.org, Marek Vasut , Richard Weinberger , Vignesh Raghavendra , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mtd: rawnand: denali: add more delays before latching incoming data Message-ID: <20200320181159.5004099f@xps13> In-Reply-To: <20200316104307.1891-1-yamada.masahiro@socionext.com> References: <20200316104307.1891-1-yamada.masahiro@socionext.com> Organization: Bootlin X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Marek, Masahiro Yamada wrote on Mon, 16 Mar 2020 19:43:07 +0900: > The Denali IP have several registers to specify how many clock cycles > should be waited between falling/rising signals. You can improve the > NAND access performance by programming these registers with optimized > values. > > Because struct nand_sdr_timings represents the device requirement > in pico seconds, denali_setup_data_interface() computes the register > values by dividing the device timings with the clock period. > > Marek Vasut reported this driver in the latest kernel does not work > on his SOCFPGA board. (The on-board NAND chip is mode 5) > > The suspicious parameter is acc_clks, so this commit relaxes it. > > The Denali NAND Flash Memory Controller User's Guide describes this > register as follows: > > acc_clks > signifies the number of bus interface clk_x clock cycles, > controller should wait from read enable going low to sending > out a strobe of clk_x for capturing of incoming data. > > Currently, acc_clks is calculated only based on tREA, the delay on the > chip side. This does not include additional delays that come from the > data path on the PCB and in the SoC, load capacity of the pins, etc. > > This relatively becomes a big factor on faster timing modes like mode 5. > > Before supporting the ->setup_data_interface() hook (e.g. Linux 4.12), > the Denali driver hacks acc_clks in a couple of ways [1] [2] to support > the timing mode 5. > > We would not go back to the hard-coded acc_clks, but we need to include > this factor into the delay somehow. Let's say the amount of the additional > delay is 10000 pico sec. > > In the new calculation, acc_clks is determined by timings->tREA_max + > data_setup_on_host. > > Also, prolong the RE# low period to make sure the data hold is met. > > Finally, re-center the data latch timing for extra safety. > > [1] https://github.com/torvalds/linux/blob/v4.12/drivers/mtd/nand/denali.c#L276 > [2] https://github.com/torvalds/linux/blob/v4.12/drivers/mtd/nand/denali.c#L282 > > Reported-by: Marek Vasut > Signed-off-by: Masahiro Yamada > --- Can you please give this patch a try and report the result? Thanks, Miquèl