{"id":2197148,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2197148/?format=json","project":{"id":28,"url":"http://patchwork.ozlabs.org/api/1.0/projects/28/?format=json","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},"msgid":"<20260217080601.3808847-10-den@valinux.co.jp>","date":"2026-02-17T08:06:01","name":"[v8,9/9] PCI: endpoint: pci-ep-msi: Add embedded eDMA doorbell fallback","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"55357f1fd7cc1a6d2d467aed2d6a22da302092d0","submitter":{"id":91573,"url":"http://patchwork.ozlabs.org/api/1.0/people/91573/?format=json","name":"Koichiro Den","email":"den@valinux.co.jp"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-pci/patch/20260217080601.3808847-10-den@valinux.co.jp/mbox/","series":[{"id":492390,"url":"http://patchwork.ozlabs.org/api/1.0/series/492390/?format=json","date":"2026-02-17T08:05:52","name":"PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback","version":8,"mbox":"http://patchwork.ozlabs.org/series/492390/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2197148/checks/","tags":{},"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=valinux.co.jp header.i=@valinux.co.jp\n header.a=rsa-sha256 header.s=selector1 header.b=ufXPRn6i;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n 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bh=grlMiPTDP7Nc9QwHhLGOZLZFADyNdipGVN7Bdny519A=;\n b=ufXPRn6iSMIfDk9NON+7LH+MhJzAnlcZBZdvWvGSM7ODYlYjc9qF/yMzaw8I7rPSckoWR9Y9ZDlHcdLKkX09boVDpLv0o7YI39uBMXihPGWsISa9X4u48VRejbUkcf3nXFIVEez9ubmXoWgAkRB0P978uxiWhhNpDs58RbtFD98=","From":"Koichiro Den ","To":"jingoohan1@gmail.com,\n\tmani@kernel.org,\n\tlpieralisi@kernel.org,\n\tkwilczynski@kernel.org,\n\trobh@kernel.org,\n\tbhelgaas@google.com,\n\theiko@sntech.de,\n\tkishon@kernel.org,\n\tjdmason@kudzu.us,\n\tdave.jiang@intel.com,\n\tallenbh@gmail.com,\n\tcassel@kernel.org,\n\tshawn.lin@rock-chips.com,\n\tFrank.Li@nxp.com","Cc":"linux-pci@vger.kernel.org,\n\tlinux-kernel@vger.kernel.org,\n\tlinux-arm-kernel@lists.infradead.org,\n\tlinux-rockchip@lists.infradead.org,\n\tntb@lists.linux.dev","Subject":"[PATCH v8 9/9] PCI: endpoint: pci-ep-msi: Add embedded eDMA doorbell\n fallback","Date":"Tue, 17 Feb 2026 17:06:01 +0900","Message-ID":"<20260217080601.3808847-10-den@valinux.co.jp>","X-Mailer":"git-send-email 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7c509650-cc41-44a2-f211-08de6dfb6c0c","X-MS-Exchange-CrossTenant-AuthSource":"TY7P286MB7722.JPNP286.PROD.OUTLOOK.COM","X-MS-Exchange-CrossTenant-AuthAs":"Internal","X-MS-Exchange-CrossTenant-OriginalArrivalTime":"17 Feb 2026 08:06:15.0993\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 LG3SrRWUpQvyLZDfhnNiIVsuIsOsqabzbUiayWJBkOgvlYT7AAMPPOqjTweqIXIsRcHPMQSmrLSkrmLieeT65Q==","X-MS-Exchange-Transport-CrossTenantHeadersStamped":"OS7P286MB7132"},"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 physical address 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\nSigned-off-by: Koichiro Den \n---\nChanges since v7:\n - Use designated initializer for consistent styling.\n - Clean up the pci_epf_alloc_doorbell() error path.\n\n drivers/pci/endpoint/pci-ep-msi.c | 96 ++++++++++++++++++++++++++++++-\n 1 file changed, 94 insertions(+), 2 deletions(-)","diff":"diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c\nindex 50badffa9d72..66f5a68c81b0 100644\n--- a/drivers/pci/endpoint/pci-ep-msi.c\n+++ b/drivers/pci/endpoint/pci-ep-msi.c\n@@ -6,6 +6,7 @@\n * Author: Frank Li \n */\n \n+#include \n #include \n #include \n #include \n@@ -36,6 +37,84 @@ 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+\tstruct device *dev = &epf->dev;\n+\tint count, ret, i;\n+\tu64 addr;\n+\n+\tcount = pci_epc_get_aux_resources(epc, epf->func_no, epf->vfunc_no,\n+\t\t\t\t\t NULL, 0);\n+\tif (count == -EOPNOTSUPP || count == 0)\n+\t\treturn -ENODEV;\n+\tif (count < 0)\n+\t\treturn count;\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 || ret == 0)\n+\t\treturn -ENODEV;\n+\tif (ret < 0)\n+\t\treturn ret;\n+\n+\tcount = ret;\n+\n+\tfor (i = 0; i < count; i++) {\n+\t\tif (res[i].type == PCI_EPC_AUX_DOORBELL_MMIO) {\n+\t\t\tif (doorbell) {\n+\t\t\t\tdev_warn(dev,\n+\t\t\t\t\t \"Duplicate DOORBELL_MMIO resource found\\n\");\n+\t\t\t\tcontinue;\n+\t\t\t}\n+\t\t\tdoorbell = &res[i];\n+\t\t}\n+\t}\n+\tif (!doorbell)\n+\t\treturn -ENODEV;\n+\n+\tmsg = kcalloc(num_db, sizeof(*msg), GFP_KERNEL);\n+\tif (!msg)\n+\t\treturn -ENOMEM;\n+\n+\taddr = doorbell->phys_addr;\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};\n+\n+\tepf->num_db = num_db;\n+\tepf->db_msg = msg;\n+\treturn 0;\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@@ -109,8 +188,21 @@ 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","prefixes":["v8","9/9"]}