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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 55D94C43457 for ; Tue, 20 Oct 2020 09:13:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E9D622242F for ; Tue, 20 Oct 2020 09:13:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391087AbgJTJND (ORCPT ); Tue, 20 Oct 2020 05:13:03 -0400 Received: from foss.arm.com ([217.140.110.172]:48364 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390971AbgJTJNC (ORCPT ); Tue, 20 Oct 2020 05:13:02 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 77E2E101E; Tue, 20 Oct 2020 02:13:01 -0700 (PDT) Received: from e121166-lin.cambridge.arm.com (e121166-lin.cambridge.arm.com [10.1.196.255]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3E2C43F66E; Tue, 20 Oct 2020 02:13:00 -0700 (PDT) Date: Tue, 20 Oct 2020 10:12:55 +0100 From: Lorenzo Pieralisi To: "Z.q. Hou" Cc: Kishon Vijay Abraham I , Bjorn Helgaas , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "robh@kernel.org" , "bhelgaas@google.com" , "gustavo.pimentel@synopsys.com" Subject: Re: [PATCH] PCI: dwc: Added link up check in map_bus of dw_child_pcie_ops Message-ID: <20201020091255.GA21678@e121166-lin.cambridge.arm.com> References: <20200916054130.8685-1-Zhiqiang.Hou@nxp.com> <20201015224738.GA24466@bjorn-Precision-5520> <7778161f-b87c-5499-b4e6-de0550bc165c@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 20, 2020 at 02:13:13AM +0000, Z.q. Hou wrote: [...] > > > For NXP Layerscape platforms (the ls1028a and ls2088a are also NXP > > Layerscape platform), as the error response to AXI/AHB was enabled, it will > > get UR error and trigger SError on AXI bus when it accesses a non-existent > > BDF on a link down bus. I'm not clear about how it happens on dra7xxx and > > imx6, since they doesn't enable the error response to AXI/AHB. > > > > That's exactly the case with DRA7xx as the error response is enabled by > > default in the platform integration. > > Got feedback from the imx6 owner that imx6 like the dra7xx has the > error response enabled by default. Now it's clear that the problem on > all these platforms is the same. Ok. Now the question is: on these platforms we trigger an SError because the link is down. If the link is down there is no point in enumerating the PCI hierarchy, is there ? If I am right the link-up check should be moved at probe time and skip enumeration if the link is down, map_bus() is not really the place where it should be - having it there is misleading and it is racy code whatever we do. We may still merge this code as a temporary workaround but the DWC drivers should be reworked to skip enumeration if the link is down. Please let me know if my reading is correct. Thanks, Lorenzo > Thanks, > Zhiqiang > > > > > Thanks > > Kishon > > > > > > > >> > > >> The backtrace below contains a bunch of irrelevant info. The > > >> timestamps are pointless. The backtrace past > > >> pci_scan_single_device+0x80/0x100 or so really doesn't add anything > > either. > > >> > > >> It'd be nice to have a comment in the code because the code *looks* > > >> wrong and racy. Without a hint, everybody who sees it will have to > > >> dig through the history to see why we tolerate the race. > > > > > > Yes, agree, but seems the cause of the SError on dra7xx and imx6 is > > different from Layerscape platforms, we need to make it clear first. > > > > > > Thanks, > > > Zhiqiang > > > > > >> > > >>> [ 0.807773] SError Interrupt on CPU2, code 0xbf000002 -- SError > > >>> [ 0.807775] CPU: 2 PID: 1 Comm: swapper/0 Not tainted > > >> 5.9.0-rc5-next-20200914-00001-gf965d3ec86fa #67 > > >>> [ 0.807776] Hardware name: LS1046A RDB Board (DT) > > >>> [ 0.807777] pstate: 20000085 (nzCv daIf -PAN -UAO BTYPE=--) > > >>> [ 0.807778] pc : pci_generic_config_read+0x3c/0xe0 > > >>> [ 0.807778] lr : pci_generic_config_read+0x24/0xe0 > > >>> [ 0.807779] sp : ffff80001003b7b0 > > >>> [ 0.807780] x29: ffff80001003b7b0 x28: ffff80001003ba74 > > >>> [ 0.807782] x27: ffff000971d96800 x26: ffff00096e77e0a8 > > >>> [ 0.807784] x25: ffff80001003b874 x24: ffff80001003b924 > > >>> [ 0.807786] x23: 0000000000000004 x22: 0000000000000000 > > >>> [ 0.807788] x21: 0000000000000000 x20: ffff80001003b874 > > >>> [ 0.807790] x19: 0000000000000004 x18: ffffffffffffffff > > >>> [ 0.807791] x17: 00000000000000c0 x16: fffffe0025981840 > > >>> [ 0.807793] x15: ffffb94c75b69948 x14: 62203a383634203a > > >>> [ 0.807795] x13: 666e6f635f726568 x12: 202c31203d207265 > > >>> [ 0.807797] x11: 626d756e3e2d7375 x10: 656877202c307830 > > >>> [ 0.807799] x9 : 203d206e66766564 x8 : 0000000000000908 > > >>> [ 0.807801] x7 : 0000000000000908 x6 : ffff800010900000 > > >>> [ 0.807802] x5 : ffff00096e77e080 x4 : 0000000000000000 > > >>> [ 0.807804] x3 : 0000000000000003 x2 : 84fa3440ff7e7000 > > >>> [ 0.807806] x1 : 0000000000000000 x0 : ffff800010034000 > > >>> [ 0.807808] Kernel panic - not syncing: Asynchronous SError > > Interrupt > > >>> [ 0.807809] CPU: 2 PID: 1 Comm: swapper/0 Not tainted > > >> 5.9.0-rc5-next-20200914-00001-gf965d3ec86fa #67 > > >>> [ 0.807810] Hardware name: LS1046A RDB Board (DT) > > >>> [ 0.807811] Call trace: > > >>> [ 0.807812] dump_backtrace+0x0/0x1c0 > > >>> [ 0.807813] show_stack+0x18/0x28 > > >>> [ 0.807814] dump_stack+0xd8/0x134 > > >>> [ 0.807814] panic+0x180/0x398 > > >>> [ 0.807815] add_taint+0x0/0xb0 > > >>> [ 0.807816] arm64_serror_panic+0x78/0x88 > > >>> [ 0.807817] do_serror+0x68/0x180 > > >>> [ 0.807818] el1_error+0x84/0x100 > > >>> [ 0.807818] pci_generic_config_read+0x3c/0xe0 > > >>> [ 0.807819] dw_pcie_rd_other_conf+0x78/0x110 > > >>> [ 0.807820] pci_bus_read_config_dword+0x88/0xe8 > > >>> [ 0.807821] pci_bus_generic_read_dev_vendor_id+0x30/0x1b0 > > >>> [ 0.807822] pci_bus_read_dev_vendor_id+0x4c/0x78 > > >>> [ 0.807823] pci_scan_single_device+0x80/0x100 > > >>> [ 0.807824] pci_scan_slot+0x38/0x130 > > >>> [ 0.807825] pci_scan_child_bus_extend+0x54/0x2a0 > > >>> [ 0.807826] pci_scan_child_bus+0x14/0x20 > > >>> [ 0.807827] pci_scan_bridge_extend+0x230/0x570 > > >>> [ 0.807828] pci_scan_child_bus_extend+0x134/0x2a0 > > >>> [ 0.807829] pci_scan_root_bus_bridge+0x64/0xf0 > > >>> [ 0.807829] pci_host_probe+0x18/0xc8 > > >>> [ 0.807830] dw_pcie_host_init+0x220/0x378 > > >>> [ 0.807831] ls_pcie_probe+0x104/0x140 > > >>> [ 0.807832] platform_drv_probe+0x54/0xa8 > > >>> [ 0.807833] really_probe+0x118/0x3e0 > > >>> [ 0.807834] driver_probe_device+0x5c/0xc0 > > >>> [ 0.807835] device_driver_attach+0x74/0x80 > > >>> [ 0.807835] __driver_attach+0x8c/0xd8 > > >>> [ 0.807836] bus_for_each_dev+0x7c/0xd8 > > >>> [ 0.807837] driver_attach+0x24/0x30 > > >>> [ 0.807838] bus_add_driver+0x154/0x200 > > >>> [ 0.807839] driver_register+0x64/0x120 > > >>> [ 0.807839] __platform_driver_probe+0x7c/0x148 > > >>> [ 0.807840] ls_pcie_driver_init+0x24/0x30 > > >>> [ 0.807841] do_one_initcall+0x60/0x1d8 > > >>> [ 0.807842] kernel_init_freeable+0x1f4/0x24c > > >>> [ 0.807843] kernel_init+0x14/0x118 > > >>> [ 0.807843] ret_from_fork+0x10/0x34 > > >>> [ 0.807854] SMP: stopping secondary CPUs > > >>> [ 0.807855] Kernel Offset: 0x394c64080000 from > > 0xffff800010000000 > > >>> [ 0.807856] PHYS_OFFSET: 0xffff8bfd40000000 > > >>> [ 0.807856] CPU features: 0x0240022,21806000 > > >>> [ 0.807857] Memory Limit: none > > >>> > > >>> Fixes: c2b0c098fbd1 ("PCI: dwc: Use generic config accessors") > > >>> Signed-off-by: Hou Zhiqiang > > >>> --- > > >>> drivers/pci/controller/dwc/pcie-designware-host.c | 6 ++++++ > > >>> 1 file changed, 6 insertions(+) > > >>> > > >>> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c > > >>> b/drivers/pci/controller/dwc/pcie-designware-host.c > > >>> index c01c9d2fb3f9..e82b518430c5 100644 > > >>> --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > >>> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > >>> @@ -442,6 +442,9 @@ static void __iomem > > >> *dw_pcie_other_conf_map_bus(struct pci_bus *bus, > > >>> struct pcie_port *pp = bus->sysdata; > > >>> struct dw_pcie *pci = to_dw_pcie_from_pp(pp); > > >>> > > >>> + if (!dw_pcie_link_up(pci)) > > >>> + return NULL; > > >>> + > > >>> busdev = PCIE_ATU_BUS(bus->number) | > > >> PCIE_ATU_DEV(PCI_SLOT(devfn)) | > > >>> PCIE_ATU_FUNC(PCI_FUNC(devfn)); > > >>> > > >>> -- > > >>> 2.17.1 > > >>>