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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 929C8C43381 for ; Tue, 19 Mar 2019 15:27:55 +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 60A2120811 for ; Tue, 19 Mar 2019 15:27:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="nF7Jtxxn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60A2120811 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.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-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=5mBDQHg4VvYUqCxSC3jFjkt+xFm4ZVlMVlMbBCwVY18=; b=nF7JtxxnJoAUeHF6AWfDLc/qg B3rGa+hqiGJiofu4d0AJS8lqZw2L+UExVhXKMP9p1RSvpdFvAdXwijBgukztyawJx/qfoF4Vk7uXh RqHggGlVnX1o4MqqGIP+JyOguwoKJkW6PSfrq6Xg2DXdqe32J2Pqcxm+n4TOwvpORm0KCK7ZWZVtN Kr4w6mlK5VSAivmHvwRhu8z56tXEeW3BdsxyyNbK6iUWtakOCCpobkpUw/rnhjiBwg/bq0p0z8sfY Jt8jYXeSAcljf/Wwv6USBxe+lhxa1OuOoFBgRvCT+ar5w+9k2saFa4RLejh+orA9J2ZjiRhhaFC2z 8Xz/yldrQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h6Ged-0004ET-Gp; Tue, 19 Mar 2019 15:27:51 +0000 Received: from mga09.intel.com ([134.134.136.24]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h6Gea-0004Dt-1h for linux-arm-kernel@lists.infradead.org; Tue, 19 Mar 2019 15:27:49 +0000 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Mar 2019 08:27:47 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,498,1544515200"; d="scan'208";a="143320633" Received: from mylly.fi.intel.com (HELO [10.237.72.176]) ([10.237.72.176]) by orsmga002.jf.intel.com with ESMTP; 19 Mar 2019 08:27:44 -0700 Subject: Re: [PATCH] [RFC] spi: pxa2xx: Do cs if restart the SSP during pxa2xx_spi_transfer_one() To: "Xiao, Jin" , Mark Brown References: <20190307072424.18820-1-jin.xiao@intel.com> <20190307160924.GE6529@sirena.org.uk> <11f165e9-ef53-edb9-cec2-e30ad2b440b5@intel.com> From: Jarkko Nikula Message-ID: <6013a37a-ee24-e371-773c-141a54926239@linux.intel.com> Date: Tue, 19 Mar 2019 17:27:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <11f165e9-ef53-edb9-cec2-e30ad2b440b5@intel.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190319_082748_154838_7E427B01 X-CRM114-Status: GOOD ( 18.14 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: yanmin.zhang@intel.com, linux-kernel@vger.kernel.org, haojian.zhuang@gmail.com, linux-spi@vger.kernel.org, bo.he@intel.com, daniel@zonque.org, robert.jarzmik@free.fr, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="windows-1252"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Jin On 3/8/19 9:28 AM, Xiao, Jin wrote: > = > Yes, the spi core has de-asserted the CS before the = > pxa2xx_spi_unprepare_transfer(). The problem on my side is that the new = > transfer will restart the SSP in pxa2xx_spi_transfer_one(). The spi core = > has asserted the CS again before restart the SSP.=A0 In my test the CS = > assert before the restart SSP can't ensure the spi transfer working = > correctly. > = I wanted to ask have you found any other fix or reason than the patches = you have sent? I've been trying to debug why the commit d5898e19c0d7 ("spi: pxa2xx: Use = core message processing loop") is causing the regression you are seeing. I've been testing this by sending two or more messages each consisting = of two 4-byte transfers through the spidev. SPI mode 3 and clock is 1 = MHz. I see only slight timing difference between a commit before and at = d5898e19c0d7 when the chip select is active. 8ae55af38817: CS act to CLK running ~40 us. CLK idle to CS deact ~26 us d5898e19c0d7: CS act to CLK running ~34 us. CLK idle to CS deact ~18 us There is more difference/variability during the times when the CS is not = active between messages. Which is understandable since there happens = message passing from userspace, queing, etc. At 8ae55af38817 total time over 2 messages varies from ~600 us to 1200 = ~us and at d5898e19c0d7 from ~500 us to 1100 us. Then at v4.19 it goes a = bit slover and varies between ~700 to 1600 us. Most probably due some = other change than in SPI subsystem as there is not commit either in SPI = core or spi-pxa2xx explaining it. Or just some random config change in = my kernel configuration between 4.17 and 4.19. What I don't understand why additional CS toggling makes it work for you = in case SSP was stopped in pxa2xx_spi_unprepare_transfer() and restarted = again in pxa2xx_spi_transfer_one(). This SSP stopping and restarting is = not visible in the SPI signals since clock is already stopped when FIFO = gets empty. I guess the reason why you are seeing pxa2xx_spi_unprepare_transfer() = only called sometimes is that in those cases where it is not called a = new SPI message got queued while processing the current one and in other = cases queue became empty before new message was queued. In both cases there shouldn't be difference in CS handling. Which makes = me scratching my head why additional CS toggling is fixing the issue in = case there is SSP restart. And which was due more time elapsed between = messages and queue went empty. -- = Jarkko _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel