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[v2,1/2] platform/surface: aggregator: Defer probing when serdev is not ready

Message ID 20240503030900.1334763-2-weifeng.liu.z@gmail.com
State New
Headers show
Series [v2,1/2] platform/surface: aggregator: Defer probing when serdev is not ready | expand

Commit Message

Weifeng Liu May 3, 2024, 3:08 a.m. UTC 
This is an attempt to alleviate race conditions in the SAM driver where
essential resources like serial device and GPIO pins are not ready at
the time ssam_serial_hub_probe() is called.  Instead of giving up
probing, a better way would be to defer the probing by returning
-EPROBE_DEFER, allowing the kernel try again later.

However, there is no way of identifying all such cases from other real
errors in a few days.  So let's take a gradual approach identify and
address these cases as they arise.  This commit marks the initial step
in this process.

Suggested-by: Maximilian Luz <luzmaximilian@gmail.com>
Reviewed-by: Maximilian Luz <luzmaximilian@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Weifeng Liu <weifeng.liu.z@gmail.com>
---
 drivers/platform/surface/aggregator/core.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/platform/surface/aggregator/core.c b/drivers/platform/surface/aggregator/core.c
index 9591a28bc38a..87dea91f91fe 100644
--- a/drivers/platform/surface/aggregator/core.c
+++ b/drivers/platform/surface/aggregator/core.c
@@ -645,9 +645,22 @@  static int ssam_serial_hub_probe(struct serdev_device *serdev)
 	/* Set up serdev device. */
 	serdev_device_set_drvdata(serdev, ctrl);
 	serdev_device_set_client_ops(serdev, &ssam_serdev_ops);
+
+	/*
+	 * The following step can fail when it's called too early before the
+	 * underlying UART device is ready (in this case -ENXIO is returned).
+	 * Instead of simply giving up and losing everything, we can defer
+	 * the probing by returning -EPROBE_DEFER so that the kernel would be
+	 * able to retry later.
+	 */
 	status = serdev_device_open(serdev);
-	if (status)
+	if (status == -ENXIO)
+		status = -EPROBE_DEFER;
+	if (status) {
+		dev_err_probe(&serdev->dev, status,
+			      "failed to open serdev device\n");
 		goto err_devopen;
+	}
 
 	astatus = ssam_serdev_setup_via_acpi(ssh->handle, serdev);
 	if (ACPI_FAILURE(astatus)) {