From: Koichiro Den <den@valinux.co.jp>
To: "Jon Mason" <jdmason@kudzu.us>,
"Dave Jiang" <dave.jiang@intel.com>,
"Allen Hubbe" <allenbh@gmail.com>,
"Manivannan Sadhasivam" <mani@kernel.org>,
"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
"Kishon Vijay Abraham I" <kishon@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Frank Li" <Frank.Li@nxp.com>,
"Jerome Brunet" <jbrunet@baylibre.com>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Niklas Cassel" <cassel@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
ntb@lists.linux.dev
Subject: [PATCH v3 05/10] PCI: endpoint: pci-epf-vntb: Implement db_vector_count/mask for doorbells
Date: Mon, 23 Mar 2026 12:15:39 +0900 [thread overview]
Message-ID: <20260323031544.2598111-6-den@valinux.co.jp> (raw)
In-Reply-To: <20260323031544.2598111-1-den@valinux.co.jp>
Implement .db_vector_count and .db_vector_mask so ntb core/clients can map
doorbell events to per-vector work and avoid the thundering-herd behavior.
pci-epf-vntb reserves two slots in db_count: slot 0 for link events and
slot 1 which is historically unused. Therefore the number of doorbell
vectors is (db_count - 2).
Report vectors as 0..N-1 and return BIT_ULL(db_vector) for the
corresponding doorbell bit. While at it, use vntb_epf_db_vector_mask()
to simplify vntb_epf_db_valid_mask().
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
drivers/pci/endpoint/functions/pci-epf-vntb.c | 36 +++++++++++++++++--
1 file changed, 34 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index d91033ab8e03..d83a9be1113f 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -1266,12 +1266,42 @@ static int vntb_epf_peer_mw_count(struct ntb_dev *ntb)
return ntb_ndev(ntb)->num_mws;
}
+static int vntb_epf_db_vector_count(struct ntb_dev *ntb)
+{
+ struct epf_ntb *ndev = ntb_ndev(ntb);
+
+ /*
+ * ndev->db_count is the total number of doorbell slots exposed to
+ * the peer, including:
+ * - slot #0 reserved for link events
+ * - slot #1 historically unused (kept for protocol compatibility)
+ *
+ * Report only usable per-vector doorbell interrupts.
+ */
+ if (ndev->db_count < EPF_IRQ_DB_START)
+ return 0;
+
+ return ndev->db_count - EPF_IRQ_DB_START;
+}
+
static u64 vntb_epf_db_valid_mask(struct ntb_dev *ntb)
{
- if (ntb_ndev(ntb)->db_count < EPF_IRQ_DB_START)
+ return BIT_ULL(vntb_epf_db_vector_count(ntb)) - 1;
+}
+
+static u64 vntb_epf_db_vector_mask(struct ntb_dev *ntb, int db_vector)
+{
+ int nr_vec;
+
+ /*
+ * Doorbell vectors are numbered [0 .. nr_vec - 1], where nr_vec
+ * excludes the two reserved slots described above.
+ */
+ nr_vec = vntb_epf_db_vector_count(ntb);
+ if (db_vector < 0 || db_vector >= nr_vec)
return 0;
- return BIT_ULL(ntb_ndev(ntb)->db_count - EPF_IRQ_DB_START) - 1;
+ return BIT_ULL(db_vector);
}
static int vntb_epf_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
@@ -1508,6 +1538,8 @@ static const struct ntb_dev_ops vntb_epf_ops = {
.spad_count = vntb_epf_spad_count,
.peer_mw_count = vntb_epf_peer_mw_count,
.db_valid_mask = vntb_epf_db_valid_mask,
+ .db_vector_count = vntb_epf_db_vector_count,
+ .db_vector_mask = vntb_epf_db_vector_mask,
.db_set_mask = vntb_epf_db_set_mask,
.mw_set_trans = vntb_epf_mw_set_trans,
.mw_clear_trans = vntb_epf_mw_clear_trans,
--
2.51.0
next prev parent reply other threads:[~2026-03-23 3:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-23 3:15 [PATCH v3 00/10] PCI: endpoint: pci-epf-vntb / NTB: epf: Enable per-doorbell bit handling Koichiro Den
2026-03-23 3:15 ` [PATCH v3 01/10] PCI: endpoint: pci-epf-vntb: Document legacy MSI doorbell offset Koichiro Den
2026-03-23 3:15 ` [PATCH v3 02/10] PCI: endpoint: pci-epf-vntb: Defer pci_epc_raise_irq() out of atomic context Koichiro Den
2026-03-23 18:27 ` Frank Li
2026-05-01 16:26 ` Manivannan Sadhasivam
2026-05-11 7:54 ` Koichiro Den
2026-03-23 3:15 ` [PATCH v3 03/10] PCI: endpoint: pci-epf-vntb: Report 0-based doorbell vector via ntb_db_event() Koichiro Den
2026-03-23 3:15 ` [PATCH v3 04/10] PCI: endpoint: pci-epf-vntb: Exclude reserved slots from db_valid_mask Koichiro Den
2026-03-23 3:15 ` Koichiro Den [this message]
2026-03-23 3:15 ` [PATCH v3 06/10] NTB: epf: Document legacy doorbell slot offset in ntb_epf_peer_db_set() Koichiro Den
2026-03-23 3:15 ` [PATCH v3 07/10] NTB: epf: Make db_valid_mask cover only real doorbell bits Koichiro Den
2026-03-23 3:15 ` [PATCH v3 08/10] NTB: epf: Report 0-based doorbell vector via ntb_db_event() Koichiro Den
2026-03-23 3:15 ` [PATCH v3 09/10] NTB: epf: Fix doorbell bitmask handling in db_read/db_clear Koichiro Den
2026-05-01 16:29 ` Manivannan Sadhasivam
2026-05-11 9:15 ` Koichiro Den
2026-03-23 3:15 ` [PATCH v3 10/10] NTB: epf: Implement db_vector_count/mask for doorbells Koichiro Den
2026-03-23 15:43 ` [PATCH v3 00/10] PCI: endpoint: pci-epf-vntb / NTB: epf: Enable per-doorbell bit handling Koichiro Den
2026-03-25 6:23 ` Niklas Cassel
2026-03-25 8:44 ` Koichiro Den
2026-04-07 15:21 ` Koichiro Den
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