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GET /api/patches/2216679/?format=api
{ "id": 2216679, "url": "http://patchwork.ozlabs.org/api/patches/2216679/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-pci/patch/20260327035422.4020455-8-den@valinux.co.jp/", "project": { "id": 28, "url": "http://patchwork.ozlabs.org/api/projects/28/?format=api", "name": "Linux PCI development", "link_name": "linux-pci", "list_id": "linux-pci.vger.kernel.org", "list_email": "linux-pci@vger.kernel.org", "web_url": null, "scm_url": null, "webscm_url": null, "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260327035422.4020455-8-den@valinux.co.jp>", "list_archive_url": null, "date": "2026-03-27T03:54:22", "name": "[v12,7/7] PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "90d41558dff34e9d99a4ab6c6b48dbde9f830283", "submitter": { "id": 91573, "url": "http://patchwork.ozlabs.org/api/people/91573/?format=api", "name": "Koichiro Den", "email": "den@valinux.co.jp" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linux-pci/patch/20260327035422.4020455-8-den@valinux.co.jp/mbox/", "series": [ { "id": 497685, "url": "http://patchwork.ozlabs.org/api/series/497685/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-pci/list/?series=497685", "date": "2026-03-27T03:54:17", "name": "PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback", "version": 12, "mbox": "http://patchwork.ozlabs.org/series/497685/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2216679/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2216679/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linux-pci+bounces-51252-incoming=patchwork.ozlabs.org@vger.kernel.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "linux-pci@vger.kernel.org" ], "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ 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h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1;\n bh=h/8fb8TGVZ2wRfIziBAcqkzxaIYB/us0nO/tCrP+47w=;\n b=lAydB4llHuuo8s4hD6w5jw3RxycAQyIUUEQhI+FIakqmdAF24x5+CILSAYlnDHYSrPmN0C++ukb4yR87Qum8uzGFkmFyCj8sljhNrDX4mzNjYjK4PtwF/2pM3TVOfIMZ2d5J9qpBJISWcsdQxt33P2gQt0lrfdkwhdOPSdSV9cSVNmyrOIV76jXHmA1/BBhLCBZWRGKiLKN7jRgYpF63VlrTnmp2Fa2GT+NSDVB1O9g0QtypCZBQAt2hJ7Zp+MLYaKIeHpljzsFby3Oi/JVdXFFNg3vzt0KUYojOJQ48q5/yxwW8s7XX+BLIyy4Jg9uNrYqLeA49P+O7ZPep4Qym+A==" ], "ARC-Authentication-Results": [ "i=2; smtp.subspace.kernel.org;\n dmarc=pass (p=none dis=none) header.from=valinux.co.jp;\n spf=pass smtp.mailfrom=valinux.co.jp;\n dkim=pass (1024-bit key) header.d=valinux.co.jp header.i=@valinux.co.jp\n header.b=wSaxy9Nm; arc=fail smtp.client-ip=52.101.229.114", "i=1; mx.microsoft.com 1; spf=pass\n smtp.mailfrom=valinux.co.jp; dmarc=pass action=none\n header.from=valinux.co.jp; dkim=pass header.d=valinux.co.jp; arc=none" ], "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed; d=valinux.co.jp;\n s=selector1;\n h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;\n bh=h/8fb8TGVZ2wRfIziBAcqkzxaIYB/us0nO/tCrP+47w=;\n b=wSaxy9Nm1a8bVklDQJb7gxbxk+eQPwCr/5aMNEtKqXHJ5ZJVuHd4bSqKtNHBwfnYLKnZqCa9lY2j4s+Z05J5+RzUa5d8lUbFiY9m+KjrDqpznmD59yXPWMH1bE5eiAf/mo8gR9WPhe8L7uazulzd0lNOdXEu3XiBT4CJEvfEG0M=", "From": "Koichiro Den <den@valinux.co.jp>", "To": "Jingoo Han <jingoohan1@gmail.com>,\n Manivannan Sadhasivam <mani@kernel.org>,\n Lorenzo Pieralisi <lpieralisi@kernel.org>, =?utf-8?q?Krzysztof_Wilczy=C5=84?=\n\t=?utf-8?q?ski?= <kwilczynski@kernel.org>, Rob Herring <robh@kernel.org>,\n Bjorn Helgaas <bhelgaas@google.com>,\n Kishon Vijay Abraham I <kishon@kernel.org>, Jon Mason <jdmason@kudzu.us>,\n Dave Jiang <dave.jiang@intel.com>, Allen Hubbe <allenbh@gmail.com>,\n Niklas Cassel <cassel@kernel.org>, Frank Li <Frank.Li@nxp.com>,\n Bhanu Seshu Kumar Valluri <bhanuseshukumar@gmail.com>,\n Marco Crivellari <marco.crivellari@suse.com>,\n Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>,\n Manikanta Maddireddy <mmaddireddy@nvidia.com>", "Cc": "linux-pci@vger.kernel.org,\n\tlinux-kernel@vger.kernel.org,\n\tntb@lists.linux.dev", "Subject": "[PATCH v12 7/7] PCI: endpoint: pci-ep-msi: Add embedded doorbell\n fallback", "Date": "Fri, 27 Mar 2026 12:54:22 +0900", "Message-ID": "<20260327035422.4020455-8-den@valinux.co.jp>", "X-Mailer": "git-send-email 2.51.0", "In-Reply-To": "<20260327035422.4020455-1-den@valinux.co.jp>", "References": "<20260327035422.4020455-1-den@valinux.co.jp>", "Content-Transfer-Encoding": "8bit", "Content-Type": "text/plain", "X-ClientProxiedBy": "TY4PR01CA0002.jpnprd01.prod.outlook.com\n (2603:1096:405:26e::19) To TY7P286MB7722.JPNP286.PROD.OUTLOOK.COM\n (2603:1096:405:38f::10)", "Precedence": "bulk", "X-Mailing-List": "linux-pci@vger.kernel.org", "List-Id": "<linux-pci.vger.kernel.org>", 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", "X-OriginatorOrg": "valinux.co.jp", "X-MS-Exchange-CrossTenant-Network-Message-Id": "\n aec3e780-6b7f-40a2-a75c-08de8bb48cdc", "X-MS-Exchange-CrossTenant-AuthSource": "TY7P286MB7722.JPNP286.PROD.OUTLOOK.COM", "X-MS-Exchange-CrossTenant-AuthAs": "Internal", "X-MS-Exchange-CrossTenant-OriginalArrivalTime": "27 Mar 2026 03:54:30.7524\n (UTC)", "X-MS-Exchange-CrossTenant-FromEntityHeader": "Hosted", "X-MS-Exchange-CrossTenant-Id": "7a57bee8-f73d-4c5f-a4f7-d72c91c8c111", "X-MS-Exchange-CrossTenant-MailboxType": "HOSTED", "X-MS-Exchange-CrossTenant-UserPrincipalName": "\n dezn0J2IiOlGeTBIvGd2QAsbUOM2qQl+CDPG1WbQCdvZ8ZUs1w/KZTsqdZYfmblCEmOkZ2AhUbGcUuRVH1TKcA==", "X-MS-Exchange-Transport-CrossTenantHeadersStamped": "TY7P286MB7090" }, "content": "Some endpoint platforms cannot use platform MSI / GIC ITS to implement\nEP-side doorbells. In those cases, EPF drivers cannot provide an\ninterrupt-driven doorbell and often fall back to polling.\n\nAdd an \"embedded\" doorbell backend that uses a controller-integrated\ndoorbell target (e.g. DesignWare integrated eDMA interrupt-emulation\ndoorbell).\n\nThe backend locates the doorbell register and a corresponding Linux IRQ\nvia the EPC aux-resource API. If the doorbell register is already\nexposed via a fixed BAR mapping, provide BAR+offset. Otherwise provide\nthe DMA address returned by dma_map_resource() (which may be an IOVA\nwhen an IOMMU is enabled) so EPF drivers can map it into BAR space.\n\nWhen MSI doorbell allocation fails with -ENODEV,\npci_epf_alloc_doorbell() falls back to this embedded backend.\n\nSuggested-by: Manivannan Sadhasivam <mani@kernel.org>\nSigned-off-by: Koichiro Den <den@valinux.co.jp>\n---\nChanges in v12:\n - Use the new pci_epc_count_aux_resources()\n - Add TODO comment and defer multiple DOORBELL_MMIO resources per EPC\n case.\n\n drivers/pci/endpoint/pci-ep-msi.c | 135 +++++++++++++++++++++++++++++-\n include/linux/pci-epf.h | 8 ++\n 2 files changed, 140 insertions(+), 3 deletions(-)", "diff": "diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c\nindex 85fe46103220..0d720556205b 100644\n--- a/drivers/pci/endpoint/pci-ep-msi.c\n+++ b/drivers/pci/endpoint/pci-ep-msi.c\n@@ -6,6 +6,8 @@\n * Author: Frank Li <Frank.Li@nxp.com>\n */\n \n+#include <linux/align.h>\n+#include <linux/cleanup.h>\n #include <linux/device.h>\n #include <linux/export.h>\n #include <linux/interrupt.h>\n@@ -36,6 +38,113 @@ static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)\n \tpci_epc_put(epc);\n }\n \n+static int pci_epf_alloc_doorbell_embedded(struct pci_epf *epf, u16 num_db)\n+{\n+\tconst struct pci_epc_aux_resource *doorbell = NULL;\n+\tstruct pci_epf_doorbell_msg *msg;\n+\tstruct pci_epc *epc = epf->epc;\n+\tsize_t map_size = 0, off = 0;\n+\tdma_addr_t iova_base = 0;\n+\tphys_addr_t phys_base;\n+\tint count, ret, i;\n+\tu64 addr;\n+\n+\tret = pci_epc_count_aux_resources(epc, epf->func_no, epf->vfunc_no,\n+\t\t\t\t\t &count);\n+\tif (ret == -EOPNOTSUPP)\n+\t\treturn -ENODEV;\n+\tif (ret)\n+\t\treturn ret;\n+\tif (!count)\n+\t\treturn -ENODEV;\n+\n+\tstruct pci_epc_aux_resource *res __free(kfree) =\n+\t\t\t\tkcalloc(count, sizeof(*res), GFP_KERNEL);\n+\tif (!res)\n+\t\treturn -ENOMEM;\n+\n+\tret = pci_epc_get_aux_resources(epc, epf->func_no, epf->vfunc_no,\n+\t\t\t\t\tres, count);\n+\tif (ret == -EOPNOTSUPP)\n+\t\treturn -ENODEV;\n+\tif (ret)\n+\t\treturn ret;\n+\n+\t/* TODO: Support multiple DOORBELL_MMIO resources per EPC. */\n+\tfor (i = 0; i < count; i++) {\n+\t\tif (res[i].type != PCI_EPC_AUX_DOORBELL_MMIO)\n+\t\t\tcontinue;\n+\n+\t\tdoorbell = &res[i];\n+\t\tbreak;\n+\t}\n+\tif (!doorbell)\n+\t\treturn -ENODEV;\n+\taddr = doorbell->phys_addr;\n+\tif (!IS_ALIGNED(addr, sizeof(u32)))\n+\t\treturn -EINVAL;\n+\n+\t/*\n+\t * Reuse the pre-exposed BAR window if available. Otherwise map the MMIO\n+\t * doorbell resource here. Any required IOMMU mapping is handled\n+\t * internally, matching the MSI doorbell semantics.\n+\t */\n+\tif (doorbell->bar == NO_BAR) {\n+\t\tphys_base = addr & PAGE_MASK;\n+\t\toff = addr - phys_base;\n+\t\tmap_size = PAGE_ALIGN(off + sizeof(u32));\n+\n+\t\tiova_base = dma_map_resource(epc->dev.parent, phys_base,\n+\t\t\t\t\t map_size, DMA_FROM_DEVICE, 0);\n+\t\tif (dma_mapping_error(epc->dev.parent, iova_base))\n+\t\t\treturn -EIO;\n+\n+\t\taddr = iova_base + off;\n+\t}\n+\n+\tmsg = kcalloc(num_db, sizeof(*msg), GFP_KERNEL);\n+\tif (!msg) {\n+\t\tret = -ENOMEM;\n+\t\tgoto err_unmap;\n+\t}\n+\n+\t/*\n+\t * Embedded doorbell backends (e.g. DesignWare eDMA interrupt emulation)\n+\t * typically provide a single IRQ and do not offer per-doorbell\n+\t * distinguishable address/data pairs. The EPC aux resource therefore\n+\t * exposes one DOORBELL_MMIO entry (u.db_mmio.irq).\n+\t *\n+\t * Still, pci_epf_alloc_doorbell() allows requesting multiple doorbells.\n+\t * For such backends we replicate the same address/data for each entry\n+\t * and mark the IRQ as shared (IRQF_SHARED). Consumers must treat them\n+\t * as equivalent \"kick\" doorbells.\n+\t */\n+\tfor (i = 0; i < num_db; i++)\n+\t\tmsg[i] = (struct pci_epf_doorbell_msg) {\n+\t\t\t.msg.address_lo = (u32)addr,\n+\t\t\t.msg.address_hi = (u32)(addr >> 32),\n+\t\t\t.msg.data = doorbell->u.db_mmio.data,\n+\t\t\t.virq = doorbell->u.db_mmio.irq,\n+\t\t\t.irq_flags = IRQF_SHARED,\n+\t\t\t.type = PCI_EPF_DOORBELL_EMBEDDED,\n+\t\t\t.bar = doorbell->bar,\n+\t\t\t.offset = (doorbell->bar == NO_BAR) ? 0 :\n+\t\t\t\t doorbell->bar_offset,\n+\t\t\t.iova_base = iova_base,\n+\t\t\t.iova_size = map_size,\n+\t\t};\n+\n+\tepf->num_db = num_db;\n+\tepf->db_msg = msg;\n+\treturn 0;\n+\n+err_unmap:\n+\tif (map_size)\n+\t\tdma_unmap_resource(epc->dev.parent, iova_base, map_size,\n+\t\t\t\t DMA_FROM_DEVICE, 0);\n+\treturn ret;\n+}\n+\n static int pci_epf_alloc_doorbell_msi(struct pci_epf *epf, u16 num_db)\n {\n \tstruct pci_epf_doorbell_msg *msg;\n@@ -109,18 +218,38 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)\n \tif (!ret)\n \t\treturn 0;\n \n-\tdev_err(dev, \"Failed to allocate doorbell: %d\\n\", ret);\n-\treturn ret;\n+\t/*\n+\t * Fall back to embedded doorbell only when platform MSI is unavailable\n+\t * for this EPC.\n+\t */\n+\tif (ret != -ENODEV)\n+\t\treturn ret;\n+\n+\tret = pci_epf_alloc_doorbell_embedded(epf, num_db);\n+\tif (ret) {\n+\t\tdev_err(dev, \"Failed to allocate doorbell: %d\\n\", ret);\n+\t\treturn ret;\n+\t}\n+\n+\tdev_info(dev, \"Using embedded (DMA) doorbell fallback\\n\");\n+\treturn 0;\n }\n EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);\n \n void pci_epf_free_doorbell(struct pci_epf *epf)\n {\n+\tstruct pci_epf_doorbell_msg *msg0;\n+\tstruct pci_epc *epc = epf->epc;\n+\n \tif (!epf->db_msg)\n \t\treturn;\n \n-\tif (epf->db_msg[0].type == PCI_EPF_DOORBELL_MSI)\n+\tmsg0 = &epf->db_msg[0];\n+\tif (msg0->type == PCI_EPF_DOORBELL_MSI)\n \t\tplatform_device_msi_free_irqs_all(epf->epc->dev.parent);\n+\telse if (msg0->type == PCI_EPF_DOORBELL_EMBEDDED && msg0->iova_size)\n+\t\tdma_unmap_resource(epc->dev.parent, msg0->iova_base,\n+\t\t\t\t msg0->iova_size, DMA_FROM_DEVICE, 0);\n \n \tkfree(epf->db_msg);\n \tepf->db_msg = NULL;\ndiff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h\nindex cd747447a1ea..8a6c64a35890 100644\n--- a/include/linux/pci-epf.h\n+++ b/include/linux/pci-epf.h\n@@ -171,6 +171,12 @@ enum pci_epf_doorbell_type {\n * (NO_BAR if not)\n * @offset: offset within @bar for the doorbell target (valid iff\n * @bar != NO_BAR)\n+ * @iova_base: Internal: base DMA address returned by dma_map_resource() for the\n+ * embedded doorbell MMIO window (used only for unmapping). Valid\n+ * when @type is PCI_EPF_DOORBELL_EMBEDDED and @iova_size is\n+ * non-zero.\n+ * @iova_size: Internal: size of the dma_map_resource() mapping at @iova_base.\n+ * Zero when no mapping was created (e.g. pre-exposed fixed BAR).\n */\n struct pci_epf_doorbell_msg {\n \tstruct msi_msg msg;\n@@ -179,6 +185,8 @@ struct pci_epf_doorbell_msg {\n \tenum pci_epf_doorbell_type type;\n \tenum pci_barno bar;\n \tresource_size_t offset;\n+\tdma_addr_t iova_base;\n+\tsize_t iova_size;\n };\n \n /**\n", "prefixes": [ "v12", "7/7" ] }