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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 165CBEB64DC for ; Mon, 3 Jul 2023 14:45:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231296AbjGCOpa (ORCPT ); Mon, 3 Jul 2023 10:45:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231355AbjGCOpL (ORCPT ); Mon, 3 Jul 2023 10:45:11 -0400 Received: from lelv0142.ext.ti.com (lelv0142.ext.ti.com [198.47.23.249]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95B6310D0; Mon, 3 Jul 2023 07:44:52 -0700 (PDT) Received: from lelv0266.itg.ti.com ([10.180.67.225]) by lelv0142.ext.ti.com (8.15.2/8.15.2) with ESMTP id 363Ei0xv066266; Mon, 3 Jul 2023 09:44:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1688395440; bh=EdzWHkf1aaa1WsMyIhRj6KpzRSMZEp4+Px5Tx9YAjRc=; h=Date:Subject:To:CC:References:From:In-Reply-To; b=Cvvw45rNa5ezhkvHMcuAWc10NurKwUE0HvRjTSWMMydmmGgNiC9nA3YLRrzIyJFdY NlSwqwbVA9Y9NOs0iSbXPAqYPkQUcXfDDXoyd5meDrFMeXhNi4x62gsXcLOtHIWj5U XbcIun2TTAZKUjKi414Oyqoz19IflfDE4HfMfPL4= Received: from DFLE115.ent.ti.com (dfle115.ent.ti.com [10.64.6.36]) by lelv0266.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 363Ei0i7034089 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 3 Jul 2023 09:44:00 -0500 Received: from DFLE103.ent.ti.com (10.64.6.24) by DFLE115.ent.ti.com (10.64.6.36) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.23; Mon, 3 Jul 2023 09:43:59 -0500 Received: from fllv0040.itg.ti.com (10.64.41.20) by DFLE103.ent.ti.com (10.64.6.24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.23 via Frontend Transport; Mon, 3 Jul 2023 09:43:59 -0500 Received: from [10.249.128.37] (ileaxei01-snat2.itg.ti.com [10.180.69.6]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id 363Eht6L097671; Mon, 3 Jul 2023 09:43:56 -0500 Message-ID: <9bb176c9-f1e6-349e-5486-74e0ea6b5012@ti.com> Date: Mon, 3 Jul 2023 20:13:55 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [EXTERNAL] Re: [PATCH] PCI: j721e: Fix delay before PERST# deassert Content-Language: en-US To: Li Chen CC: Vignesh Raghavendra , Tom Joseph , Lorenzo Pieralisi , Krzysztof Wilczy_ski , Rob Herring , Bjorn Helgaas , linux-omap , linux-pci , linux-arm-kernel , linux-kernel References: <20230703112914.68806-1-a-verma1@ti.com> <1891c041807.fea67a55448140.3454059194195387266@linux.beauty> From: "Verma, Achal" In-Reply-To: <1891c041807.fea67a55448140.3454059194195387266@linux.beauty> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/3/2023 7:19 PM, Li Chen wrote: > Hi Achal, > ---- On Mon, 03 Jul 2023 19:29:14 +0800 Achal Verma wrote --- > > As per the PCIe Card Electromechanical specification REV. 3.0, PERST# > > signal should be de-asserted after minimum 100ms from the time power-rails > > become stable. Current delay of 100us is observed to be not enough on some > > custom platform implemented using TI's K3 SOCs. > > > > So, to ensure 100ms delay to give sufficient time for power-rails and > > refclk to become stable, change delay from 100us to 100ms. > > What problems could arise if the delay is too small? Would some endpoints not be able to detect it? If delay is small, cpu stall is reported during probe() while accessing PCIe registers in some cases. > > Regards, > Li