linux-kernel - [PATCH] PCI: endpoint: pci-epf-test: Move DMA check into read/write/copy functions

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Message-Id: <20240806162756.607002-1-rick.wertenbroek@gmail.com>
Date: Tue,  6 Aug 2024 18:27:54 +0200
From: Rick Wertenbroek <rick.wertenbroek@...il.com>
To: rick.wertenbroek@...g-vd.ch
Cc: dlemoal@...nel.org,
	alberto.dassatti@...g-vd.ch,
	Rick Wertenbroek <rick.wertenbroek@...il.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Niklas Cassel <cassel@...nel.org>,
	Frank Li <Frank.Li@....com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] PCI: endpoint: pci-epf-test: Move DMA check into read/write/copy functions

The test for a DMA transfer was done in pci_epf_test_cmd_handler, which
if not supported would lead to the endpoint function just printing an
error message and waiting for further commands. This would leave the
host side PCI driver waiting for an interrupt because the call to
pci_epf_test_raise_irq is skipped. The host side driver
drivers/misc/pci_endpoint_test.c would hang indefinitely when sending
a transfer request with DMA if the endpoint does not support it.
This is because wait_for_completion() is used in the host side driver.

Move the DMA check into the read/write/copy functions so that they
report a transfer (IO) error so that pci_epf_test_raise_irq() is
called when a transfer with DMA is requested, even if unsupported.

The host side driver will still report an error on transfer thanks
to the checksum, because no data was moved, but will not hang anymore
waiting for an interrupt that will never arrive.

Signed-off-by: Rick Wertenbroek <rick.wertenbroek@...il.com>
---
 drivers/pci/endpoint/functions/pci-epf-test.c | 29 +++++++++++++++----
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 7c2ed6eae53a..bd4b37f46f41 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -314,6 +314,17 @@ static void pci_epf_test_print_rate(struct pci_epf_test *epf_test,
 		 (u64)ts.tv_sec, (u32)ts.tv_nsec, rate);
 }
 
+static int pci_epf_test_check_dma(struct pci_epf_test *epf_test,
+				   struct pci_epf_test_reg *reg)
+{
+	if ((READ_ONCE(reg->flags) & FLAG_USE_DMA) &&
+	    !epf_test->dma_supported) {
+		dev_err(&epf_test->epf->dev, "Cannot transfer data using DMA\n");
+		return -EIO;
+	}
+	return 0;
+}
+
 static void pci_epf_test_copy(struct pci_epf_test *epf_test,
 			      struct pci_epf_test_reg *reg)
 {
@@ -327,6 +338,10 @@ static void pci_epf_test_copy(struct pci_epf_test *epf_test,
 	struct device *dev = &epf->dev;
 	struct pci_epc *epc = epf->epc;
 
+	ret = pci_epf_test_check_dma(epf_test, reg);
+	if (ret)
+		goto err;
+
 	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");
@@ -423,6 +438,10 @@ static void pci_epf_test_read(struct pci_epf_test *epf_test,
 	struct pci_epc *epc = epf->epc;
 	struct device *dma_dev = epf->epc->dev.parent;
 
+	ret = pci_epf_test_check_dma(epf_test, reg);
+	if (ret)
+		goto err;
+
 	src_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, reg->size);
 	if (!src_addr) {
 		dev_err(dev, "Failed to allocate address\n");
@@ -507,6 +526,10 @@ static void pci_epf_test_write(struct pci_epf_test *epf_test,
 	struct pci_epc *epc = epf->epc;
 	struct device *dma_dev = epf->epc->dev.parent;
 
+	ret = pci_epf_test_check_dma(epf_test, reg);
+	if (ret)
+		goto err;
+
 	dst_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, reg->size);
 	if (!dst_addr) {
 		dev_err(dev, "Failed to allocate address\n");
@@ -647,12 +670,6 @@ static void pci_epf_test_cmd_handler(struct work_struct *work)
 	WRITE_ONCE(reg->command, 0);
 	WRITE_ONCE(reg->status, 0);
 
-	if ((READ_ONCE(reg->flags) & FLAG_USE_DMA) &&
-	    !epf_test->dma_supported) {
-		dev_err(dev, "Cannot transfer data using DMA\n");
-		goto reset_handler;
-	}
-
 	if (reg->irq_type > IRQ_TYPE_MSIX) {
 		dev_err(dev, "Failed to detect IRQ type\n");
 		goto reset_handler;
-- 
2.25.1