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PCI: endpoint: pci-epf-vntb: Implement .db_vector_count()/mask() for doorbells

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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. Build db_valid_mask from a validated vector
count so out-of-range db_count values cannot create invalid shifts.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260513024923.451765-8-den@valinux.co.jp
This commit is contained in:
Koichiro Den
2026-05-13 11:49:18 +09:00
committed by Bjorn Helgaas
parent 823468a4ea
commit 2579f3f7f5
1 changed files with 41 additions and 3 deletions
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44
drivers/pci/endpoint/functions/pci-epf-vntb.c
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@@ -1362,12 +1362,48 @@ static int vntb_epf_peer_mw_count(struct ntb_dev *ntb)
return ntb_ndev(ntb)->num_mws;
}
static u64 vntb_epf_db_valid_mask(struct ntb_dev *ntb)
static int vntb_epf_db_vector_count(struct ntb_dev *ntb)
{
if (ntb_ndev(ntb)->db_count < EPF_IRQ_DB_START)
struct epf_ntb *ndev = ntb_ndev(ntb);
u32 db_count = READ_ONCE(ndev->db_count);
/*
* 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 (db_count < MIN_DB_COUNT || db_count > MAX_DB_COUNT)
return 0;
return BIT_ULL(ntb_ndev(ntb)->db_count - EPF_IRQ_DB_START) - 1;
return db_count - EPF_IRQ_DB_START;
}
static u64 vntb_epf_db_valid_mask(struct ntb_dev *ntb)
{
int nr_vec = vntb_epf_db_vector_count(ntb);
if (!nr_vec)
return 0;
return GENMASK_ULL(nr_vec - 1, 0);
}
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(db_vector);
}
static int vntb_epf_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
@@ -1617,6 +1653,8 @@ 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,