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 51CE7CE7B08 for ; Thu, 28 Sep 2023 07:52:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230497AbjI1Hwe (ORCPT ); Thu, 28 Sep 2023 03:52:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49564 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230435AbjI1Hwe (ORCPT ); Thu, 28 Sep 2023 03:52:34 -0400 Received: from fllv0015.ext.ti.com (fllv0015.ext.ti.com [198.47.19.141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3FB38F; Thu, 28 Sep 2023 00:52:32 -0700 (PDT) Received: from lelv0266.itg.ti.com ([10.180.67.225]) by fllv0015.ext.ti.com (8.15.2/8.15.2) with ESMTP id 38S7q3jD043240; Thu, 28 Sep 2023 02:52:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1695887523; bh=8+LtU1GWGtZKrm76UQzPWGPiwukPzZ3p1SrdAE68OKY=; h=Date:Subject:To:CC:References:From:In-Reply-To; b=n8vUYXefbk48fkOKgox4HfoIjPn/so74vwZO0Q3DDjEIWs/uJDWUv63KF8G5ygJyQ bsADS/msBoSHMR6WTJrM6I2OXhCPU2A+AbvcCvcU9PwNj/GOtiVfDvKqlGXIvD5J93 Uz9p0lK47h7/EsdaWYg4wqYg7Trccclwnp3omtJE= Received: from DFLE100.ent.ti.com (dfle100.ent.ti.com [10.64.6.21]) by lelv0266.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 38S7q3q0083043 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 28 Sep 2023 02:52:03 -0500 Received: from DFLE109.ent.ti.com (10.64.6.30) by DFLE100.ent.ti.com (10.64.6.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.23; Thu, 28 Sep 2023 02:52:03 -0500 Received: from fllv0040.itg.ti.com (10.64.41.20) by DFLE109.ent.ti.com (10.64.6.30) 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; Thu, 28 Sep 2023 02:52:03 -0500 Received: from [172.24.227.83] (ileaxei01-snat.itg.ti.com [10.180.69.5]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id 38S7px6C066514; Thu, 28 Sep 2023 02:52:00 -0500 Message-ID: <3f0ba0d6-6027-6f2c-b548-4bbd0f69bc89@ti.com> Date: Thu, 28 Sep 2023 13:21:58 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH v3] PCI: keystone: Fix race condition when initializing PHYs Content-Language: en-US To: Siddharth Vadapalli , , , , CC: , , , , , References: <20230927041845.1222080-1-s-vadapalli@ti.com> From: Ravi Gunasekaran In-Reply-To: <20230927041845.1222080-1-s-vadapalli@ti.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 9/27/23 9:48 AM, Siddharth Vadapalli wrote: > The PCI driver invokes the PHY APIs using the ks_pcie_enable_phy() > function. The PHY in this case is the Serdes. It is possible that the > PCI instance is configured for 2 lane operation across two different > Serdes instances, using 1 lane of each Serdes. In such a configuration, > if the reference clock for one Serdes is provided by the other Serdes, > it results in a race condition. After the Serdes providing the reference > clock is initialized by the PCI driver by invoking its PHY APIs, it is > not guaranteed that this Serdes remains powered on long enough for the > PHY APIs based initialization of the dependent Serdes. In such cases, > the PLL of the dependent Serdes fails to lock due to the absence of the > reference clock from the former Serdes which has been powered off by the > PM Core. > > Fix this by obtaining reference to the PHYs before invoking the PHY > initialization APIs and releasing reference after the initialization is > complete. Sounds reasonable. Acked-by: Ravi Gunasekaran Ravi > > Fixes: 49229238ab47 ("PCI: keystone: Cleanup PHY handling") > Signed-off-by: Siddharth Vadapalli > --- > > NOTE: This patch is based on linux-next tagged next-20230927. > > v2: > https://lore.kernel.org/r/20230926063638.1005124-1-s-vadapalli@ti.com/ > > Changes since v2: > - Implement suggestion by Ilpo Järvinen > moving the phy_pm_runtime_put_sync() For-Loop section before the > return value of ks_pcie_enable_phy(ks_pcie) is checked, thereby > preventing duplication of the For-Loop. > - Rebase patch on next-20230927. > > v1: > https://lore.kernel.org/r/20230926054200.963803-1-s-vadapalli@ti.com/ > > Changes since v1: > - Add code to release reference(s) to the phy(s) when > ks_pcie_enable_phy(ks_pcie) fails. > > Regards, > Siddharth. > > drivers/pci/controller/dwc/pci-keystone.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/pci/controller/dwc/pci-keystone.c b/drivers/pci/controller/dwc/pci-keystone.c > index 49aea6ce3e87..0ec6720cc2df 100644 > --- a/drivers/pci/controller/dwc/pci-keystone.c > +++ b/drivers/pci/controller/dwc/pci-keystone.c > @@ -1218,7 +1218,16 @@ static int __init ks_pcie_probe(struct platform_device *pdev) > goto err_link; > } > > + /* Obtain reference(s) to the phy(s) */ > + for (i = 0; i < num_lanes; i++) > + phy_pm_runtime_get_sync(ks_pcie->phy[i]); > + > ret = ks_pcie_enable_phy(ks_pcie); > + > + /* Release reference(s) to the phy(s) */ > + for (i = 0; i < num_lanes; i++) > + phy_pm_runtime_put_sync(ks_pcie->phy[i]); > + > if (ret) { > dev_err(dev, "failed to enable phy\n"); > goto err_link; -- Regards, Ravi