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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 9D5CDC001DE for ; Wed, 2 Aug 2023 09:08:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:CC:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=rNwJjl/84VgZK68W1BkN9If4sWJ4S6M/TkPcexRZ3cs=; b=mniSnwmckurbPQ rXx5tzDm8A0ZJLMFLCLv02aTlBYZdp2xm8C1QbrqhEtcR8lu9HLvvGZOMoGelmFbvAmXQq/eOQtOO 3w/24llc+bnwxYXchpCtKLRCt2uz1PdQmTwJL3vuTBt6YlT+QBaWnIcnbH/BVzQdAEcAbu3uIXCJI IbczEHCAEieCHod1HPp5KfUWndWs2eqmCAIBJky207AGOgB3Nm0MYN8p6NmqiCatjKg9z3WSynbu+ V9MarjBmbyTkx08Wms30ITAceD+hMlh4daqHbrNu7Y0F0BzF2CgVXvwaRtRczFVsipRfvFokcM+Rz WP5FexF3r0xcOJl1dsiw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qR7qA-004RpM-1k; Wed, 02 Aug 2023 09:08:22 +0000 Received: from lelv0143.ext.ti.com ([198.47.23.248]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qR7q7-004Rlz-2E for linux-arm-kernel@lists.infradead.org; Wed, 02 Aug 2023 09:08:21 +0000 Received: from fllv0034.itg.ti.com ([10.64.40.246]) by lelv0143.ext.ti.com (8.15.2/8.15.2) with ESMTP id 372988cG025542; Wed, 2 Aug 2023 04:08:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1690967288; bh=sVfGcElZUqw1E2kyfrVI8It33Bquda6ZK7Bym2RIWlg=; h=Date:Subject:To:CC:References:From:In-Reply-To; b=A1WQmC15S+g2k4FIBBgdiz2C1eMHcX6Jsv2vkNsniyPe6cobYkcTJtwg/cKmLAbB6 OHE3n+JQ7Oi+a1fBvijrfM/827b3NX/+vrqyC4Vx5upJOnuroGo3MqoyQKyFMAU9oW pkA5r8dkqfd/i9v56XJNKab2qD6aY/PcsM9Q1tcc= Received: from DLEE111.ent.ti.com (dlee111.ent.ti.com [157.170.170.22]) by fllv0034.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 372988xu024201 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 2 Aug 2023 04:08:08 -0500 Received: from DLEE105.ent.ti.com (157.170.170.35) by DLEE111.ent.ti.com (157.170.170.22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.23; Wed, 2 Aug 2023 04:08:08 -0500 Received: from fllv0040.itg.ti.com (10.64.41.20) by DLEE105.ent.ti.com (157.170.170.35) 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; Wed, 2 Aug 2023 04:08:08 -0500 Received: from [172.24.19.15] (ileaxei01-snat2.itg.ti.com [10.180.69.6]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id 372983Nh119753; Wed, 2 Aug 2023 04:08:03 -0500 Message-ID: <8951d4fd-279d-8a78-65a3-daeb4befa899@ti.com> Date: Wed, 2 Aug 2023 14:38:02 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [EXTERNAL] Re: [PATCH v3] PCI: j721e: Delay 100ms T_PVPERL from power stable to PERST# inactive To: Bjorn Helgaas CC: Vignesh Raghavendra , Lorenzo Pieralisi , Krzysztof Wilczy_ski , Rob Herring , Bjorn Helgaas , , , , , Achal Verma References: <20230718155515.GA483233@bhelgaas> Content-Language: en-US From: "Verma, Achal" In-Reply-To: <20230718155515.GA483233@bhelgaas> X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230802_020819_828353_FB6D87A4 X-CRM114-Status: GOOD ( 31.20 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 7/18/2023 9:25 PM, Bjorn Helgaas wrote: > On Fri, Jul 07, 2023 at 03:21:19PM +0530, Achal Verma wrote: >> As per the PCIe Card Electromechanical specification REV. 5.0, PERST# >> signal should be de-asserted after minimum 100ms from the time power-rails >> become stable. So, to ensure 100ms delay to give sufficient time for >> power-rails and refclk to become stable, change delay from 100us to 100ms. >> >> From PCIe Card Electromechanical specification REV. 5.0 section 2.9.2: >> TPVPERL: Power stable to PERST# inactive - 100ms >> >> Fixes: f3e25911a430 ("PCI: j721e: Add TI J721E PCIe driver") >> Signed-off-by: Achal Verma >> --- >> >> Changes from v2: >> * Fix commit message. >> >> Change from v1: >> * Add macro for delay value. >> >> drivers/pci/controller/cadence/pci-j721e.c | 11 +++++------ >> drivers/pci/pci.h | 2 ++ >> 2 files changed, 7 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c >> index e70213c9060a..32b6a7dc3cff 100644 >> --- a/drivers/pci/controller/cadence/pci-j721e.c >> +++ b/drivers/pci/controller/cadence/pci-j721e.c >> @@ -498,14 +498,13 @@ static int j721e_pcie_probe(struct platform_device *pdev) >> >> /* >> * "Power Sequencing and Reset Signal Timings" table in >> - * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 3.0 >> - * indicates PERST# should be deasserted after minimum of 100us >> - * once REFCLK is stable. The REFCLK to the connector in RC >> - * mode is selected while enabling the PHY. So deassert PERST# >> - * after 100 us. >> + * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 5.0 >> + * indicates PERST# should be deasserted after minimum of 100ms >> + * after power rails achieve specified operating limits and >> + * within this period reference clock should also become stable. > > I think the problem is not that the current code is *wrong*, because > we do need to observe T_PERST-CLK, but that it failed to *also* > account for T_PVPERL. > > There are two delays before deasserting PERST#: > > T_PVPERL: delay after power becomes stable > T_PERST-CLK: delay after REFCLK becomes stable > > I assume power is enabled by phy_power_on(), and REFCLK is enabled by > clk_prepare_enable(): > > cdns_pcie_init_phy > cdns_pcie_enable_phy > phy_power_on <-- power becomes stable > clk_prepare_enable <-- REFCLK becomes stable > if (gpiod) > usleep_range > gpiod_set_value_cansleep(gpiod, 1) <-- deassert PERST# > > I don't actually know if phy_power_on() guarantees that power is > stable before it returns. But I guess that's our assumption? > Similarly for clk_prepare_enable(). > > In any case, we have to observe both delays. They overlap, and > T_PVPERL is 1000 times longer than T_PERST-CLK, so there might be > enough slop in an msleep(100) to cover both, but I think I would do > the simple-minded: > > msleep(PCIE_TPVPERL_MS); > usleep_range(PCIE_TPERST_CLK_US, 2 * PCIE_TPERST_CLK_US); > I think adding 100us more is not required since as you said and as also mentioned in CEM spec, 100ms covers for both power rails and refclock to get stable and 2 consecutive sleep call looks different to me. But if still required (please let me know), will do the suggested change, along with other fixes you asked below. > This is slightly more conservative than necessary because they > overlap, but at least it shows that we thought about both of them. > >> if (gpiod) { >> - usleep_range(100, 200); >> + msleep(PCIE_TPVPERL_DELAY_MS); >> gpiod_set_value_cansleep(gpiod, 1); > > I wish this local variable were named something like "perst_gpiod" > instead of "gpiod". We already know from its use in > gpiod_set_value_cansleep() that it's a GPIO. What's NOT obvious from > the context is that this is the PERST# signal. sure will change variable name to perst_gpiod. > > Tangent: it looks like the DT "reset" property that I'm assuming > controls PERST# is optional. How do we enforce these delays if that > property is missing? > yes gpiod_get shouldn't be optional, will fix this too. >> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h >> index a4c397434057..6ab2367e5867 100644 >> --- a/drivers/pci/pci.h >> +++ b/drivers/pci/pci.h >> @@ -13,6 +13,8 @@ >> >> #define PCIE_LINK_RETRAIN_TIMEOUT_MS 1000 >> >> +#define PCIE_TPVPERL_DELAY_MS 100 /* see PCIe CEM r5.0, sec 2.9.2 */ >> + >> extern const unsigned char pcie_link_speed[]; >> extern bool pci_early_dump; >> >> -- >> 2.25.1 >> >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel