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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 EF188C4332D for ; Fri, 12 Mar 2021 10:21:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B7C2364FFD for ; Fri, 12 Mar 2021 10:21:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233343AbhCLKUf (ORCPT ); Fri, 12 Mar 2021 05:20:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232920AbhCLKUR (ORCPT ); Fri, 12 Mar 2021 05:20:17 -0500 Received: from ssl.serverraum.org (ssl.serverraum.org [IPv6:2a01:4f8:151:8464::1:2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 88B7BC061574; Fri, 12 Mar 2021 02:20:17 -0800 (PST) Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 4848322235; Fri, 12 Mar 2021 11:20:15 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1615544415; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7AwJyDsly/A7V+5RW+umEy+/kfZBbndM17q5qch0pqs=; b=EC0cBBXxN04ASMeKveVSaUo+vYHbtl7LcZarVqKmw9+bat/GbF2Epq/Y9JOx5BwD1X4Tbv 7ViqqBwt3I0tPDVP6DT7D1wrmEoYlT/xT+EiwfRmMmjKFeaympr/GTTRbaHbDfGLxBPU6l WBe87kMZ92vdrhYhqQJIfhbqXkY3n5U= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Fri, 12 Mar 2021 11:20:15 +0100 From: Michael Walle To: Pratyush Yadav Cc: Tudor.Ambarus@microchip.com, nm@ti.com, kristo@kernel.org, robh+dt@kernel.org, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, broonie@kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-spi@vger.kernel.org, lokeshvutla@ti.com Subject: Re: [RFC PATCH 0/6] spi: Add OSPI PHY calibration support for spi-cadence-quadspi In-Reply-To: <20210312101036.jfz2733ssv4nhfey@ti.com> References: <20210311191216.7363-1-p.yadav@ti.com> <9c551f56-4c00-b41a-f051-8b7e197fbcdc@microchip.com> <20210312101036.jfz2733ssv4nhfey@ti.com> User-Agent: Roundcube Webmail/1.4.11 Message-ID: <676386736df5e5b22e34b0b5af91c894@walle.cc> X-Sender: michael@walle.cc Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 2021-03-12 11:10, schrieb Pratyush Yadav: > There is usually a delay from when the flash drives the data line (IOW, > puts a data bit on it) and when the signal reaches the controller. This > delay can vary by the flash, board, silicon characteristics, > temperature, etc. Temperature might change over time, but the calibration is only done once. I don't know how much influence the temperature actually has, but our boards are usually operating from -40°C to +85°C. So there might be a possible temperature difference of 125K between actual calibration and when the flash is accessed. -michael