From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zhou Wang Subject: Re: [PATCH] ACPI/IORT: Fix PCI ACS enablement Date: Thu, 21 Sep 2017 19:32:58 +0800 Message-ID: <59C3A36A.2060202@hisilicon.com> References: <20170919170539.6265-1-lorenzo.pieralisi@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: Received: from szxga04-in.huawei.com ([45.249.212.190]:6960 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751436AbdIULdF (ORCPT ); Thu, 21 Sep 2017 07:33:05 -0400 In-Reply-To: <20170919170539.6265-1-lorenzo.pieralisi@arm.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Lorenzo Pieralisi , linux-acpi@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, Will Deacon , Robin Murphy , Alex Williamson On 2017/9/20 1:05, Lorenzo Pieralisi wrote: > commit f6810c15cf97 ("iommu/arm-smmu: Clean up early-probing > workarounds") removed kernel code that was allowing to initialize > and probe the SMMU devices early (ie earlier than PCI devices through > linker script callback entries) in the boot process because it was not > needed any longer in that the SMMU devices/drivers now support deferred > probing. > > Since the SMMUs probe routines are also in charge of requesting global > PCI ACS kernel enablement, commit f6810c15cf97 ("iommu/arm-smmu: Clean > up early-probing workarounds") also postponed PCI ACS enablement to > SMMUs devices probe time, which may be too late given that PCI devices > needs to detect if PCI ACS is enabled to init the respective capability > through the following call path: > > pci_device_add() > -> pci_init_capabilities() > -> pci_enable_acs() > > Add code in the ACPI IORT SMMU platform devices initialization path > (that is called before ACPI PCI enumeration) to detect if an SMMU is > present in HW and enable PCI ACS if it actually is, restoring the > correct PCI ACS enablement sequencing. > > Fixes: f6810c15cf97 ("iommu/arm-smmu: Clean up early-probing > Signed-workarounds") > Signed-off-by: Lorenzo Pieralisi > Cc: Will Deacon > Cc: Robin Murphy > Cc: Zhou Wang > Cc: Alex Williamson > --- > drivers/acpi/arm64/iort.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c > index 9565d57..71a7694 100644 > --- a/drivers/acpi/arm64/iort.c > +++ b/drivers/acpi/arm64/iort.c > @@ -1184,6 +1184,7 @@ static void __init iort_init_platform_devices(void) > struct acpi_table_iort *iort; > struct fwnode_handle *fwnode; > int i, ret; > + bool smmu_detected = false; > > /* > * iort_table and iort both point to the start of IORT table, but > @@ -1218,11 +1219,21 @@ static void __init iort_init_platform_devices(void) > acpi_free_fwnode_static(fwnode); > return; > } > + > + smmu_detected = true; > } > > iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort_node, > iort_node->length); > } > + > + /* > + * If IORT reports an SMMU component make sure PCI ACS is > + * requested so that PCI devices can enable it in their > + * capabilities. > + */ > + if (smmu_detected) > + pci_request_acs(); > } > > void __init acpi_iort_init(void) > Hi Lorenzo, I tested this patch, it works well in my HiSilicon Hip08 based system. However, setting ACS flag at the stage of SMMU device init seems not good, I mean what if in one system there are only platform devices connected to SMMU device. Best, Zhou