diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index f630393e8208..9b791f4a7ffb 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -330,6 +330,10 @@ static int pci_epf_test_copy(struct pci_epf_test *epf_test, bool use_dma)
 	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
 	volatile struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
 
+	dev_dbg(&epf->dev,
+		"COPY src addr 0x%llx, dst addr 0x%llx, %u B\n",
+		reg->src_addr, reg->dst_addr, reg->size);
+
 	src_addr = pci_epc_mem_alloc_addr(epc, &src_phys_addr, reg->size);
 	if (!src_addr) {
 		dev_err(dev, "Failed to allocate source address\n");
@@ -380,6 +384,8 @@ static int pci_epf_test_copy(struct pci_epf_test *epf_test, bool use_dma)
 
 		buf = kzalloc(reg->size, GFP_KERNEL);
 		if (!buf) {
+			dev_err(dev, "Alloc %zu B for copy failed\n",
+				(size_t)reg->size);
 			ret = -ENOMEM;
 			goto err_map_addr;
 		}
@@ -424,6 +430,9 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test, bool use_dma)
 	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
 	volatile struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
 
+	dev_dbg(&epf->dev, "READ src addr 0x%llx, %u B\n",
+		reg->src_addr, reg->size);
+
 	src_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, reg->size);
 	if (!src_addr) {
 		dev_err(dev, "Failed to allocate address\n");
@@ -442,6 +451,8 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test, bool use_dma)
 
 	buf = kzalloc(reg->size, GFP_KERNEL);
 	if (!buf) {
+		dev_err(dev, "Alloc %zu B for read failed\n",
+			(size_t)reg->size);
 		ret = -ENOMEM;
 		goto err_map_addr;
 	}
@@ -506,6 +517,9 @@ static int pci_epf_test_write(struct pci_epf_test *epf_test, bool use_dma)
 	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
 	volatile struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
 
+	dev_dbg(&epf->dev, "WRITE dst addr 0x%llx, %u B\n",
+		reg->dst_addr, reg->size);
+
 	dst_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, reg->size);
 	if (!dst_addr) {
 		dev_err(dev, "Failed to allocate address\n");
@@ -524,6 +538,8 @@ static int pci_epf_test_write(struct pci_epf_test *epf_test, bool use_dma)
 
 	buf = kzalloc(reg->size, GFP_KERNEL);
 	if (!buf) {
+		dev_err(dev, "Alloc %zu B for write failed\n",
+			(size_t)reg->size);
 		ret = -ENOMEM;
 		goto err_map_addr;
 	}
@@ -580,7 +596,7 @@ static int pci_epf_test_write(struct pci_epf_test *epf_test, bool use_dma)
 	return ret;
 }
 
-static void pci_epf_test_raise_irq(struct pci_epf_test *epf_test, u8 irq_type,
+static int pci_epf_test_raise_irq(struct pci_epf_test *epf_test, u8 irq_type,
 				   u16 irq)
 {
 	struct pci_epf *epf = epf_test->epf;
@@ -588,26 +604,35 @@ static void pci_epf_test_raise_irq(struct pci_epf_test *epf_test, u8 irq_type,
 	struct pci_epc *epc = epf->epc;
 	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
 	volatile struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
+	int ret;
 
 	reg->status |= STATUS_IRQ_RAISED;
 
 	switch (irq_type) {
 	case IRQ_TYPE_LEGACY:
-		pci_epc_raise_irq(epc, epf->func_no, epf->vfunc_no,
-				  PCI_EPC_IRQ_LEGACY, 0);
+		dev_dbg(&epf->dev, "RAISE legacy IRQ\n");
+		ret = pci_epc_raise_irq(epc, epf->func_no, epf->vfunc_no,
+					PCI_EPC_IRQ_LEGACY, 0);
 		break;
 	case IRQ_TYPE_MSI:
-		pci_epc_raise_irq(epc, epf->func_no, epf->vfunc_no,
-				  PCI_EPC_IRQ_MSI, irq);
+		dev_dbg(&epf->dev, "RAISE MSI IRQ %d\n", (int)irq);
+		ret = pci_epc_raise_irq(epc, epf->func_no, epf->vfunc_no,
+					PCI_EPC_IRQ_MSI, irq);
 		break;
 	case IRQ_TYPE_MSIX:
-		pci_epc_raise_irq(epc, epf->func_no, epf->vfunc_no,
-				  PCI_EPC_IRQ_MSIX, irq);
+		dev_dbg(&epf->dev, "RAISE MSIX IRQ %d\n", (int)irq);
+		ret = pci_epc_raise_irq(epc, epf->func_no, epf->vfunc_no,
+					PCI_EPC_IRQ_MSIX, irq);
 		break;
 	default:
 		dev_err(dev, "Failed to raise IRQ, unknown type\n");
-		break;
+		return -EINVAL;
 	}
+
+	if (ret)
+		dev_err(dev, "Raise IRQ failed %d\n", ret);
+
+	return ret;
 }
 
 static void pci_epf_test_cmd_handler(struct work_struct *work)
@@ -684,8 +709,11 @@ static void pci_epf_test_cmd_handler(struct work_struct *work)
 
 	if (command & COMMAND_RAISE_MSI_IRQ) {
 		count = pci_epc_get_msi(epc, epf->func_no, epf->vfunc_no);
-		if (reg->irq_number > count || count <= 0)
+		if (reg->irq_number > count || count <= 0) {
+			dev_err(dev, "Invalid MSI %d / %d\n",
+				(int)reg->irq_number, (int)count);
 			goto reset_handler;
+		}
 		reg->status = STATUS_IRQ_RAISED;
 		pci_epc_raise_irq(epc, epf->func_no, epf->vfunc_no,
 				  PCI_EPC_IRQ_MSI, reg->irq_number);
@@ -694,14 +722,19 @@ static void pci_epf_test_cmd_handler(struct work_struct *work)
 
 	if (command & COMMAND_RAISE_MSIX_IRQ) {
 		count = pci_epc_get_msix(epc, epf->func_no, epf->vfunc_no);
-		if (reg->irq_number > count || count <= 0)
+		if (reg->irq_number > count || count <= 0) {
+			dev_err(dev, "Invalid MSIX %d / %d\n",
+				(int)reg->irq_number, (int)count);
 			goto reset_handler;
+		}
 		reg->status = STATUS_IRQ_RAISED;
 		pci_epc_raise_irq(epc, epf->func_no, epf->vfunc_no,
 				  PCI_EPC_IRQ_MSIX, reg->irq_number);
 		goto reset_handler;
 	}
 
+	dev_err(dev, "Unknown command 0x%x\n", command);
+
 reset_handler:
 	queue_delayed_work(kpcitest_workqueue, &epf_test->cmd_handler,
 			   msecs_to_jiffies(1));
@@ -828,12 +861,14 @@ static int pci_epf_test_notifier(struct notifier_block *nb, unsigned long val,
 
 	switch (val) {
 	case CORE_INIT:
+		dev_dbg(&epf->dev, "CORE_INIT event\n");
 		ret = pci_epf_test_core_init(epf);
 		if (ret)
 			return NOTIFY_BAD;
 		break;
 
 	case LINK_UP:
+		dev_dbg(&epf->dev, "LINK_UP event\n");
 		queue_delayed_work(kpcitest_workqueue, &epf_test->cmd_handler,
 				   msecs_to_jiffies(1));
 		break;
@@ -875,8 +910,12 @@ static int pci_epf_test_alloc_space(struct pci_epf *epf)
 	test_reg_size = test_reg_bar_size + msix_table_size + pba_size;
 
 	if (epc_features->bar_fixed_size[test_reg_bar]) {
-		if (test_reg_size > bar_size[test_reg_bar])
+		if (test_reg_size > bar_size[test_reg_bar]) {
+			dev_err(&epf->dev, "BAR %d: %zu B > %zu B\n",
+				(int)test_reg_bar, test_reg_size,
+				(size_t)bar_size[test_reg_bar]);
 			return -ENOMEM;
+		}
 		test_reg_size = bar_size[test_reg_bar];
 	}
 
@@ -938,8 +977,10 @@ static int pci_epf_test_bind(struct pci_epf *epf)
 	bool linkup_notifier = false;
 	bool core_init_notifier = false;
 
-	if (WARN_ON_ONCE(!epc))
+	if (WARN_ON_ONCE(!epc)) {
+		dev_err(&epf->dev, "No controller\n");
 		return -EINVAL;
+	}
 
 	epc_features = pci_epc_get_features(epc, epf->func_no, epf->vfunc_no);
 	if (!epc_features) {
@@ -950,8 +991,10 @@ static int pci_epf_test_bind(struct pci_epf *epf)
 	linkup_notifier = epc_features->linkup_notifier;
 	core_init_notifier = epc_features->core_init_notifier;
 	test_reg_bar = pci_epc_get_first_free_bar(epc_features);
-	if (test_reg_bar < 0)
+	if (test_reg_bar < 0) {
+		dev_err(&epf->dev, "No free BAR\n");
 		return -EINVAL;
+	}
 	pci_epf_configure_bar(epf, epc_features);
 
 	epf_test->test_reg_bar = test_reg_bar;
