[PATCH 1/2] misc: pci_endpoint_test: Fix doorbell success logic

[Niklas Cassel <cassel@kernel.org>]

The following was observed:
pci-endpoint-test 0000:01:00.0: Failed to trigger doorbell in endpoint
ok 23 pcie_ep_doorbell.DOORBELL_TEST

We observed a bug where an EPC driver would send two IRQs during ENABLE
DOORBELL command.

Because we got two IRQs for a single command, test->irq_raised.done was
never decreased to zero by complete(), so the
wait_for_completion_timeout() after the writel() that rings the doorbell
would return immediately, before the endpoint had managed to set
STATUS_DOORBELL_SUCCESS and triggered an IRQ corresponding to that write.

Later, when re-reading the status after disabling the doorbell,
STATUS_DOORBELL_SUCCESS will have been set by the endpoint, thus we would
not fail the test case.

Improve the test case logic such that if we failed to trigger the doorbell
in the endpoint, we make sure that we also fail the test case.

Fixes: eefb83790a0d ("misc: pci_endpoint_test: Add doorbell test case")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/misc/pci_endpoint_test.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
index 3635741c3e7a..26ab9252251f 100644
--- a/drivers/misc/pci_endpoint_test.c
+++ b/drivers/misc/pci_endpoint_test.c
@@ -1071,6 +1071,7 @@ static int pci_endpoint_test_doorbell(struct pci_endpoint_test *test)
 	struct pci_dev *pdev = test->pdev;
 	struct device *dev = &pdev->dev;
 	int irq_type = test->irq_type;
+	int ret = 0;
 	enum pci_barno bar;
 	u32 data, status;
 	u32 addr;
@@ -1119,8 +1120,11 @@ static int pci_endpoint_test_doorbell(struct pci_endpoint_test *test)
 
 	status = pci_endpoint_test_readl(test, PCI_ENDPOINT_TEST_STATUS);
 
-	if (!left || !(status & STATUS_DOORBELL_SUCCESS))
+	if (!left || !(status & STATUS_DOORBELL_SUCCESS)) {
 		dev_err(dev, "Failed to trigger doorbell in endpoint\n");
+		/* Store error code, but continue to disable doorbell. */
+		ret = -EINVAL;
+	}
 
 	pci_endpoint_test_writel(test, PCI_ENDPOINT_TEST_COMMAND,
 				 COMMAND_DISABLE_DOORBELL);
@@ -1134,10 +1138,7 @@ static int pci_endpoint_test_doorbell(struct pci_endpoint_test *test)
 		return -EINVAL;
 	}
 
-	if (!(status & STATUS_DOORBELL_SUCCESS))
-		return -EINVAL;
-
-	return 0;
+	return ret;
 }
 
 static long pci_endpoint_test_ioctl(struct file *file, unsigned int cmd,
-- 
2.55.0