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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 2A1B9C43603 for ; Mon, 9 Dec 2019 02:35:46 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DE6CD206DB for ; Mon, 9 Dec 2019 02:35:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="HecdXnGV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE6CD206DB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=socionext.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:References: In-Reply-To:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Z1EQQTw9H/2ZdMDrpxDh+gVVLUxNm8mLLHlbwm7BPB0=; b=HecdXnGVL+qgKF CTBT9FRValKRtCeFhPlkQ06U6TDY12NZBxHjMVyfxmhU3xS86pNFwQ0rCHKAl2K0SezHPyv+pPLNc HJiShRSBacmloXz5qJMnXlVE1WSYAdiiPGWk7I8R1Ck9J44lVLDt3eauXOTSDQCE7EuZdPL/+LDXZ PuNTONOVGEYmQZ3aT4kS77/m5F/x4xxGjspIQJikx/w/dnRTWAaPMLRU6dFT7D3OVCcqt64068CDy kktV+IE8zhw0ncqSSPJ+jO5pIi7c1gWTB7TACMzVn2hgLl9kugV5Ery56EUd941WEgQ2HpXab0Gxa cHWoTo9X2EeHy9Ew/3yg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1ie8tl-00062R-Az; Mon, 09 Dec 2019 02:35:45 +0000 Received: from mx.socionext.com ([202.248.49.38]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1ie8ti-000619-2V for linux-arm-kernel@lists.infradead.org; Mon, 09 Dec 2019 02:35:44 +0000 Received: from unknown (HELO iyokan-ex.css.socionext.com) ([172.31.9.54]) by mx.socionext.com with ESMTP; 09 Dec 2019 11:35:37 +0900 Received: from mail.mfilter.local (m-filter-1 [10.213.24.61]) by iyokan-ex.css.socionext.com (Postfix) with ESMTP id B67FE603AB; Mon, 9 Dec 2019 11:35:37 +0900 (JST) Received: from 172.31.9.53 (172.31.9.53) by m-FILTER with ESMTP; Mon, 9 Dec 2019 11:36:06 +0900 Received: from yuzu.css.socionext.com (yuzu [172.31.8.45]) by iyokan.css.socionext.com (Postfix) with ESMTP id 3907F40372; Mon, 9 Dec 2019 11:35:37 +0900 (JST) Received: from [10.213.132.48] (unknown [10.213.132.48]) by yuzu.css.socionext.com (Postfix) with ESMTP id 0C6CE120456; Mon, 9 Dec 2019 11:35:37 +0900 (JST) Date: Mon, 09 Dec 2019 11:35:37 +0900 From: Kunihiko Hayashi To: Kishon Vijay Abraham I Subject: Re: [PATCH 2/2] PCI: uniphier: Add checking whether PERST# is deasserted In-Reply-To: <6b288f46-452d-6f92-728c-56c4100028cf@ti.com> References: <20191206175813.E6B2.4A936039@socionext.com> <6b288f46-452d-6f92-728c-56c4100028cf@ti.com> Message-Id: <20191209113536.E9DD.4A936039@socionext.com> MIME-Version: 1.0 X-Mailer: Becky! ver. 2.70 [ja] X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191208_183542_350837_A2CB5782 X-CRM114-Status: GOOD ( 27.24 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Lorenzo Pieralisi , Masami Hiramatsu , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Jassi Brar , Bjorn Helgaas , Andrew Murray , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Kishon, On Fri, 6 Dec 2019 14:31:17 +0530 wrote: > Hi, > > On 06/12/19 2:28 pm, Kunihiko Hayashi wrote: > > Hi Kishon, > > > On Fri, 6 Dec 2019 12:28:29 +0530 wrote: > > >> Hi, > >> > >> On 04/12/19 3:35 pm, Kunihiko Hayashi wrote: > >>> On Fri, 22 Nov 2019 20:53:16 +0900 wrote: > >>>>> Hello Lorenzo, > >>>> > >>>> On Thu, 21 Nov 2019 16:47:05 +0000 wrote: > >>>> > >>>>> On Fri, Nov 08, 2019 at 04:30:27PM +0900, Kunihiko Hayashi wrote: > >>>>>>> However, If I understand correctly, doesn't your solution only work some > >>>>>>> of the time? What happens if you boot both machines at the same time, > >>>>>>> and PERST# isn't asserted prior to the kernel booting? > >>>>>> > >>>>>> I think it contains an annoying problem. > >>>>>> > >>>>>> If PERST# isn't toggled prior to the kernel booting, PERST# remains asserted > >>>>>> and the RC driver can't access PCI bus. > >>>>>> > >>>>>> As a result, this patch works and deasserts PERST# (and EP configuration will > >>>>>> be lost). So boot sequence needs to include deasserting PERST#. > >>>>> > >>>>> I am sorry but I have lost you. Can you explain to us why checking > >>>>> that PERST# is deasserted guarantees you that: > >>>>> > >>>>> - The EP has bootstrapped > >>>>> - It is safe not to toggle it again (and also skip > >>>>> uniphier_pcie_ltssm_enable()) > >>>>> > >>>>> Please provide details of the HW configuration so that we understand > >>>>> what's actually supposed to happen and why this patch fixes the > >>>>> issue you are facing. > >>>> > >>>> I tried to connect between the following boards, and do pci-epf-test: > >>>> - "RC board": UniPhier ld20 board that has DWC RC controller > >>>> - "EP board": UniPhier legacy board that has DWC EP controller > >>>> > >>>> This EP has power-on-state configuration, but it's necessary to set > >>>> class ID, BAR sizes, etc. after starting up. > >>>> > >>>> In case of that starting up RC board before EP board, the RC driver > >>>> can't establish link. So we need to boot EP board first. > >>>> At that point, I've considered why RC can't establish link, > >>> and found that the waitng time was too short. > >>>> - EP/RC: power on both boards > >>>> - RC: start up the kernel on RC board > >>>> - RC: wait for link up (long time enough) > >>>> - EP: start up the kernel on EP board > >>>> - EP: configurate pci-epf-test > >>>> When the endpoint configuration is done and the EP driver enables LTSSM, > >>> the RC driver will quit from waiting for link up. > >>>> Currently DWC RC driver calls dwc_pcie_wait_for_link(), however, > >>> the function tries to link up 10 times only, that is defined > >>> as LINK_WAIT_MAX_RETRIES in pcie-designware.h, it's too short > >>> to configurate the endpoint. > >>>> Now the patch to bypass PERST# is not necessary. > >>>> Instead for DWC RC drivers, I think that the number of retries > >>> should be changed according to the usage. > >>> And the same issue remains with other RC drivers. > >> > >> If EP is configured using Linux, then PERST# cannot be used as it's difficult to boot linux and initialize EP within the specified time interval. Can't you prevent PERST from being propagated at all? > > > Surely it might be difficult for RC to decide the time to wait for EP. > > Since RC almost toggles PERST# in boot time, I'd like to think about > > how to prevent from first PERST# at least. > > It can be prevented in the HW (If that's possible). I modify the cable connecting RC and EP to not propagate PERST#. I understand. Although it's possible in case of a cable, in case of an edge connector, EP side needs hardware mechanism not to propagate PERST#. Thank you, --- Best Regards, Kunihiko Hayashi _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel