PCI: endpoint: pci-epf-test: Reuse pre-exposed doorbell targets

pci-epf-test advertises the doorbell target to the RC as a BAR number
and an offset, and the RC rings the doorbell with a single DWORD MMIO
write.

Some doorbell backends may report that the doorbell target is already
exposed via a platform-owned fixed BAR (db_msg[0].bar/offset). In that
case, reuse the pre-exposed window and do not reprogram the BAR with
pci_epc_set_bar().

Also honor db_msg[0].irq_flags when requesting the doorbell IRQ, and
only restore the original BAR mapping on disable if pci-epf-test
programmed it.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
[bhelgaas: wrap comment]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260414141514.1341429-7-den@valinux.co.jp

1 files changed, 59 insertions, 27 deletions

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 591d301fa89d..4802d4f80f78 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -94,6 +94,7 @@ struct pci_epf_test {
 	bool			dma_private;
 	const struct pci_epc_features *epc_features;
 	struct pci_epf_bar	db_bar;
+	bool			db_bar_programmed;
 	size_t			bar_size[PCI_STD_NUM_BARS];
 };
 
@@ -733,7 +734,9 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
 {
 	u32 status = le32_to_cpu(reg->status);
 	struct pci_epf *epf = epf_test->epf;
+	struct pci_epf_doorbell_msg *db;
 	struct pci_epc *epc = epf->epc;
+	unsigned long irq_flags;
 	struct msi_msg *msg;
 	enum pci_barno bar;
 	size_t offset;
@@ -743,13 +746,28 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
 	if (ret)
 		goto set_status_err;
 
-	msg = &epf->db_msg[0].msg;
-	bar = pci_epc_get_next_free_bar(epf_test->epc_features, epf_test->test_reg_bar + 1);
-	if (bar < BAR_0)
-		goto err_doorbell_cleanup;
+	db = &epf->db_msg[0];
+	msg = &db->msg;
+	epf_test->db_bar_programmed = false;
+
+	if (db->bar != NO_BAR) {
+		/*
+		 * The doorbell target is already exposed via a platform-owned
+		 * fixed BAR
+		 */
+		bar = db->bar;
+		offset = db->offset;
+	} else {
+		bar = pci_epc_get_next_free_bar(epf_test->epc_features,
+						epf_test->test_reg_bar + 1);
+		if (bar < BAR_0)
+			goto err_doorbell_cleanup;
+	}
+
+	irq_flags = epf->db_msg[0].irq_flags | IRQF_ONESHOT;
 
 	ret = request_threaded_irq(epf->db_msg[0].virq, NULL,
-				   pci_epf_test_doorbell_handler, IRQF_ONESHOT,
+				   pci_epf_test_doorbell_handler, irq_flags,
 				   "pci-ep-test-doorbell", epf_test);
 	if (ret) {
 		dev_err(&epf->dev,
@@ -761,22 +779,30 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
 	reg->doorbell_data = cpu_to_le32(msg->data);
 	reg->doorbell_bar = cpu_to_le32(bar);
 
-	msg = &epf->db_msg[0].msg;
-	ret = pci_epf_align_inbound_addr(epf, bar, ((u64)msg->address_hi << 32) | msg->address_lo,
-					 &epf_test->db_bar.phys_addr, &offset);
+	if (db->bar == NO_BAR) {
+		ret = pci_epf_align_inbound_addr(epf, bar,
+						 ((u64)msg->address_hi << 32) |
+						 msg->address_lo,
+						 &epf_test->db_bar.phys_addr,
+						 &offset);
 
-	if (ret)
-		goto err_free_irq;
+		if (ret)
+			goto err_free_irq;
+	}
 
 	reg->doorbell_offset = cpu_to_le32(offset);
 
-	epf_test->db_bar.barno = bar;
-	epf_test->db_bar.size = epf->bar[bar].size;
-	epf_test->db_bar.flags = epf->bar[bar].flags;
+	if (db->bar == NO_BAR) {
+		epf_test->db_bar.barno = bar;
+		epf_test->db_bar.size = epf->bar[bar].size;
+		epf_test->db_bar.flags = epf->bar[bar].flags;
 
-	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf_test->db_bar);
-	if (ret)
-		goto err_free_irq;
+		ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf_test->db_bar);
+		if (ret)
+			goto err_free_irq;
+
+		epf_test->db_bar_programmed = true;
+	}
 
 	status |= STATUS_DOORBELL_ENABLE_SUCCESS;
 	reg->status = cpu_to_le32(status);
@@ -806,17 +832,23 @@ static void pci_epf_test_disable_doorbell(struct pci_epf_test *epf_test,
 	free_irq(epf->db_msg[0].virq, epf_test);
 	pci_epf_test_doorbell_cleanup(epf_test);
 
-	/*
-	 * The doorbell feature temporarily overrides the inbound translation
-	 * to point to the address stored in epf_test->db_bar.phys_addr, i.e.,
-	 * it calls set_bar() twice without ever calling clear_bar(), as
-	 * calling clear_bar() would clear the BAR's PCI address assigned by
-	 * the host. Thus, when disabling the doorbell, restore the inbound
-	 * translation to point to the memory allocated for the BAR.
-	 */
-	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf->bar[bar]);
-	if (ret)
-		goto set_status_err;
+	if (epf_test->db_bar_programmed) {
+		/*
+		 * The doorbell feature temporarily overrides the inbound
+		 * translation to point to the address stored in
+		 * epf_test->db_bar.phys_addr, i.e., it calls set_bar()
+		 * twice without ever calling clear_bar(), as calling
+		 * clear_bar() would clear the BAR's PCI address assigned
+		 * by the host. Thus, when disabling the doorbell, restore
+		 * the inbound translation to point to the memory allocated
+		 * for the BAR.
+		 */
+		ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf->bar[bar]);
+		if (ret)
+			goto set_status_err;
+
+		epf_test->db_bar_programmed = false;
+	}
 
 	status |= STATUS_DOORBELL_DISABLE_SUCCESS;
 	reg->status = cpu_to_le32(status);