From nobody Tue Feb 10 05:44:45 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 58BF51EDA2C; Fri, 2 Jan 2026 15:35:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767368105; cv=none; b=p8i29vxLIpwTiWVZ8euU5p9EYtSWgsaak+mVsk4Kj4Dam2vIwI1Z9nABBaRPAPETrDvs1DAXHxg70NiwXgvBVr9ePCGnIpfRM8ps2WACta6Qq7k8++xjiXaNADdoDwnw0tj8UplasERINeZK5haQPWuT2/NvS6PQIRfAT0fvhKg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767368105; c=relaxed/simple; bh=1TILJpA94tm+NjdIdR07UOJcYaE5858nIVxioO1NGMI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Sjd3FzSj10hduITREmtpR0acgm8cQ5Iv7ugDLSJ37xmtoJYmgPwJxa+kD0wGs9vANwgmckEyJjRml5WWyMyimM0/EmGei7CBhjtqtudXQJS3yjob5sjqgwoW3C/kVL6e6AHN1Tm9XiAotHsRCEdDBplL59Pl5gw/cYJJ6ICKH18= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=N6qnuSRk; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="N6qnuSRk" Received: by smtp.kernel.org (Postfix) with ESMTPS id 721B9C116D0; Fri, 2 Jan 2026 15:35:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767368104; bh=1TILJpA94tm+NjdIdR07UOJcYaE5858nIVxioO1NGMI=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=N6qnuSRkrvEWVnBqyYtCTYC9Lol5VkOc29JzXXnqjJBfu35/hYItKoLx970sCqftc d0WKm9j+dcGywT+8dercKKJRbJfgey2qqF3fTMYv19uVQLukB3xTgQ0YVS0ToIMFos N42/Be6Jrp86UsVBswkXnsicQF8xjjR1utHMn9bs+7DYttQ3R/+OsZc2Yn6zf+aSsT RybdDAOhboySkxTRCzXM7AbM+KBOWulR4m9+Wmma5DQw0oJhYM5G1VwutqW228akUU inHDRCEm+GK4vYDMftmx00uD6OdQwVsa4TT2jumMq5DXO31phrPZQWjpw2FYiqAvqw 6zRNc6dLtNAJw== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 599A7FA3752; Fri, 2 Jan 2026 15:35:04 +0000 (UTC) From: Manivannan Sadhasivam via B4 Relay Date: Fri, 02 Jan 2026 21:04:47 +0530 Subject: [PATCH v3 1/4] PCI: Enable ACS only after configuring IOMMU for OF platforms Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260102-pci_acs-v3-1-72280b94d288@oss.qualcomm.com> References: <20260102-pci_acs-v3-0-72280b94d288@oss.qualcomm.com> In-Reply-To: <20260102-pci_acs-v3-0-72280b94d288@oss.qualcomm.com> To: Bjorn Helgaas Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, Naresh Kamboju , Pavankumar Kondeti , Xingang Wang , Marek Szyprowski , Robin Murphy , Jason Gunthorpe , Manivannan Sadhasivam , Manivannan Sadhasivam X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=3997; i=manivannan.sadhasivam@oss.qualcomm.com; h=from:subject:message-id; bh=5UbTaCqlSfsZh3mFkk650olnLwfrJC/TA0PViCutZMg=; b=owEBbQGS/pANAwAKAVWfEeb+kc71AcsmYgBpV+Wm1DB6YPxGpFaNimOGigjiqMZEILNVe2hId 3WdA7gPUuuJATMEAAEKAB0WIQRnpUMqgUjL2KRYJ5dVnxHm/pHO9QUCaVflpgAKCRBVnxHm/pHO 9QyWCACWSH1UrGgxuShZFc3H/mSHakZIiuUJWYNWLHowr0+LG8fEbpljGe1qbrPwdfHJmvIq7Nr 4dhgOIWLCncoAc8uEbHVP7XhFQCoYrdIF5fQQR4mgAFUgPSBzY2LF6Fzt3YRNvMJQqWb7QIpknh 1qbq7JPK+S4tG4ggD28ap67z4rmqU/11MNPQ65qzR9toO1KCeLPc12WFBG0AbLI5uWgNqTuyYgy 2xgi/XqW+/8jf3NpQKwpJCAxA5u01SMJtFvLSZ1UgAFiU9sIaW7MGLDjSfAuWKa0kXGbYLwrhjo 0VNbn2LxYQvyN2+kZMgz3K7NOdcE9F+KX/1jtC1PZvtHFirE X-Developer-Key: i=manivannan.sadhasivam@oss.qualcomm.com; a=openpgp; fpr=C668AEC3C3188E4C611465E7488550E901166008 X-Endpoint-Received: by B4 Relay for manivannan.sadhasivam@oss.qualcomm.com/default with auth_id=461 X-Original-From: Manivannan Sadhasivam Reply-To: manivannan.sadhasivam@oss.qualcomm.com From: Manivannan Sadhasivam For enabling ACS without the cmdline params, the platform drivers are expected to call pci_request_acs() API which sets a static flag, 'pci_acs_enable' in drivers/pci/pci.c. And this flag is used to enable ACS in pci_enable_acs() helper, which gets called during pci_acs_init(), as per this call stack: -> pci_device_add() -> pci_init_capabilities() -> pci_acs_init() /* check for pci_acs_enable */ -> pci_enable_acs() For the OF platforms, pci_request_acs() is called during of_iommu_configure() during device_add(), as per this call stack: -> device_add() -> iommu_bus_notifier() -> iommu_probe_device() -> pci_dma_configure() -> of_dma_configure() -> of_iommu_configure() /* set pci_acs_enable */ -> pci_request_acs() As seen from both call stacks, pci_enable_acs() is called way before the invocation of pci_request_acs() for the OF platforms. This means, pci_enable_acs() will not enable ACS for the first device that gets enumerated, which is usally the Root Port device. But since the static flag, 'pci_acs_enable' is set *afterwards*, ACS will be enabled for the ACS capable devices enumerated later. To fix this issue, do not call pci_enable_acs() from pci_acs_init(), but only from pci_dma_configure() after calling of_dma_configure(). This makes sure that pci_enable_acs() only gets called after the IOMMU framework has called pci_request_acs(). The ACS enablement flow now looks like: -> pci_device_add() -> pci_init_capabilities() /* Just store the ACS cap */ -> pci_acs_init() -> device_add() ... -> pci_dma_configure() -> of_dma_configure() -> pci_request_acs() -> pci_enable_acs() For the ACPI platforms, pci_request_acs() is called during ACPI initialization time itself, independent of the IOMMU framework. Tested-by: Marek Szyprowski Tested-by: Naresh Kamboju Signed-off-by: Manivannan Sadhasivam --- drivers/pci/pci-driver.c | 8 ++++++++ drivers/pci/pci.c | 8 -------- drivers/pci/pci.h | 1 + 3 files changed, 9 insertions(+), 8 deletions(-) diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 7c2d9d596258..301a9418e38e 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -1650,6 +1650,14 @@ static int pci_dma_configure(struct device *dev) ret =3D acpi_dma_configure(dev, acpi_get_dma_attr(adev)); } =20 + /* + * Attempt to enable ACS regardless of capability because some Root + * Ports (e.g. those quirked with *_intel_pch_acs_*) do not have + * the standard ACS capability but still support ACS via those + * quirks. + */ + pci_enable_acs(to_pci_dev(dev)); + pci_put_host_bridge_device(bridge); =20 /* @drv may not be valid when we're called from the IOMMU layer */ diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 13dbb405dc31..2c3d0a2d6973 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3648,14 +3648,6 @@ bool pci_acs_path_enabled(struct pci_dev *start, void pci_acs_init(struct pci_dev *dev) { dev->acs_cap =3D pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS); - - /* - * Attempt to enable ACS regardless of capability because some Root - * Ports (e.g. those quirked with *_intel_pch_acs_*) do not have - * the standard ACS capability but still support ACS via those - * quirks. - */ - pci_enable_acs(dev); } =20 /** diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 0e67014aa001..4592ede0ebcc 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -939,6 +939,7 @@ static inline resource_size_t pci_resource_alignment(st= ruct pci_dev *dev, } =20 void pci_acs_init(struct pci_dev *dev); +void pci_enable_acs(struct pci_dev *dev); #ifdef CONFIG_PCI_QUIRKS int pci_dev_specific_acs_enabled(struct pci_dev *dev, u16 acs_flags); int pci_dev_specific_enable_acs(struct pci_dev *dev); --=20 2.48.1