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 35B6BCCA479 for ; Mon, 18 Jul 2022 18:56:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229798AbiGRS4T (ORCPT ); Mon, 18 Jul 2022 14:56:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50918 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233328AbiGRS4R (ORCPT ); Mon, 18 Jul 2022 14:56:17 -0400 Received: from mail-ej1-x632.google.com (mail-ej1-x632.google.com [IPv6:2a00:1450:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A05492F03E for ; Mon, 18 Jul 2022 11:56:16 -0700 (PDT) Received: by mail-ej1-x632.google.com with SMTP id va17so23075712ejb.0 for ; Mon, 18 Jul 2022 11:56:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=C0WOvyoqadjpEITlMzRPBvEYMnXCNxGE7c+O0MJD504=; b=XJS5FZ5zhEAEbuqi8Y+6fkRVJQrliRRdil1M7NY2CTQks7BLEwTQuEAYfRgWfB3/Nn wT+tzwHbFutPe0fLqbfiThThbqHXRVSJ+eIqDsQQE6z7ZnhSZ8SgiCNJDQIjxGwtY7vO 6SIjv38OPKevyHhfzIXydxSSPltWYNqYa5fyw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=C0WOvyoqadjpEITlMzRPBvEYMnXCNxGE7c+O0MJD504=; b=C+Ys8rvlnjcymmIHeRzavNG3y2Okki4SgoApQYJju03wZNd1t6aK+NCj2qyEFdJAE+ EWu7/0WtNOSDz7fJ0ZNnNGcC3ap9DSymQSAQAVdFPPI678lx39IgZHmTiMHRQjkfTjHe fa6oT9fV/jwlmiwWVTJ/1lw9bSoRof3uZt8H4VZGaPt72rPZJeteNyWGcKiBhsHrn9/H 0duSnZ+HByHgb5a4tp4BTY0F6sNN936gxsKYqdz4imi08MXHdETi8cMgCSwnsOtJTgti G0CEA5K1b04iJij4rYp/09FueOTN0yU5o3631SgGj/tIQ+HSgjLdylSM9lZZl9v+10a0 6mzg== X-Gm-Message-State: AJIora8yHVpJAH/DmbGevcFeyh6IhshWOQWzPsGaMwTl8OM5lhWSDOdm NhzHOjW3XzSr0U8/R8aaFzYFcWvjT55fIop3oZ3NkQ== X-Google-Smtp-Source: AGRyM1uo031Zdy22MbXpwGfGpcKqCn6IvBlAnm7yWcskFnaXLXp81/Bd6TlVQEXSCslz3eJkrirRKWfcSpzZwaICnwg= X-Received: by 2002:a17:907:9809:b0:72f:817:d433 with SMTP id ji9-20020a170907980900b0072f0817d433mr14173469ejc.483.1658170575172; Mon, 18 Jul 2022 11:56:15 -0700 (PDT) MIME-Version: 1.0 References: <20220716222454.29914-3-jim2101024@gmail.com> <20220718181425.GA1431580@bhelgaas> In-Reply-To: <20220718181425.GA1431580@bhelgaas> From: Jim Quinlan Date: Mon, 18 Jul 2022 14:56:03 -0400 Message-ID: Subject: Re: [PATCH v2 2/6] PCI: brcmstb: Split brcm_pcie_setup() into two funcs To: Bjorn Helgaas Cc: Jim Quinlan , "open list:PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS" , Nicolas Saenz Julienne , Bjorn Helgaas , Lorenzo Pieralisi , Cyril Brulebois , "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" , Florian Fainelli , Lorenzo Pieralisi , Rob Herring , =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= , "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" , "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" , open list Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="0000000000001ffb6705e418eccc" Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org --0000000000001ffb6705e418eccc Content-Type: text/plain; charset="UTF-8" On Mon, Jul 18, 2022 at 2:14 PM Bjorn Helgaas wrote: > > On Sat, Jul 16, 2022 at 06:24:49PM -0400, Jim Quinlan wrote: > > Currently, the function does the setup for establishing PCIe link-up > > with the downstream device, and it does the actual link-up as well. > > The calling sequence is (roughly) the following in the probe: > > > > -> brcm_pcie_probe() > > -> brcm_pcie_setup(); /* Set-up and link-up */ > > -> pci_host_probe(bridge); > > > > This commit splits the setup function in two: brcm_pcie_setup(), which only > > does the set-up, and brcm_pcie_start_link(), which only does the link-up. > > The reason why we are doing this is to lay a foundation for subsequent > > commits so that we can turn on any power regulators, as described in the > > root port's DT node, prior to doing link-up. > > All drivers that care about power regulators turn them on before > link-up, but typically those regulators are described directly under > the host bridge itself. Hi Bjorn, Actually, what you describe is what I proposed with my v1 back in Nov 2020. The binding commit message said, "Quite similar to the regulator bindings found in "rockchip-pcie-host.txt", this allows optional regulators to be attached and controlled by the PCIe RC driver." > > IIUC the difference here is that you have regulators described under > Root Ports (not the host bridge/Root Complex itself), so you don't > know about them until you've enumerated the Root Ports. > brcm_pcie_probe() can't turn them on directly because it doesn't know > what Root Ports are present and doesn't know about regulators below > them. The reviewer's requested me to move the regulator node(s) elsewhere, and at some point later it was requested to be placed under the Root Port driver. I would love to return them under the host bridge, just say the word! > > So I think brcm_pcie_setup() does initialization that doesn't depend > on the link or any downstream devices, and brcm_pcie_start_link() does > things that depend on the link being up. Right? Yes. > > If so, "start_link" might be a slight misnomer since AFAICT > brcm_pcie_start_link() doesn't do anything to initiate link-up except > maybe deasserting fundamental reset. Some drivers start the LTSSM or > explicitly enable link training, but brcm_pcie_start_link() doesn't > seem to do anything like that. > > brcm_pcie_start_link() still does brcm_pcie_set_outbound_win(). Does > that really depend on the link being up? If that only affects the > Root Port, maybe it could be done before link-up? Some of the registers cannot be accessed until after linkup but these do not have that issue. I will change this. Jim Quinlan Broadcom STB > > > We do this by defining an > > add_bus() callback which is invoked during enumeraion. At the end of this > > patchset the probe function trace will look something like this: > > > > -> brcm_pcie_probe() > > -> brcm_pcie_setup(); /* Set-up only */ > > -> pci_host_probe(bridge); > > -> [enumeration] > > -> pci_alloc_child_bus() > > -> bus->ops->add_bus(bus); /* We've set this op */ > > -> brcm_pcie_add_bus() /* Our callback */ > > -> [turn on regulators] /* Main objective! */ > > -> brcm_pcie_start_link() /* Link-up */ --0000000000001ffb6705e418eccc Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIIQbgYJKoZIhvcNAQcCoIIQXzCCEFsCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg gg3FMIIFDTCCA/WgAwIBAgIQeEqpED+lv77edQixNJMdADANBgkqhkiG9w0BAQsFADBMMSAwHgYD VQQLExdHbG9iYWxTaWduIFJvb3QgQ0EgLSBSMzETMBEGA1UEChMKR2xvYmFsU2lnbjETMBEGA1UE AxMKR2xvYmFsU2lnbjAeFw0yMDA5MTYwMDAwMDBaFw0yODA5MTYwMDAwMDBaMFsxCzAJBgNVBAYT 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