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@xxxxxxxxx>
Reviewed-by: Maximilian Luz <luzmaximilian@xxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Acked-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Signed-off-by: Weifeng Liu <weifeng.liu.z@xxxxxxxxx>
---
drivers/platform/surface/aggregator/core.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/platform/surface/aggregator/core.c b/drivers/platform/surface/aggregator/core.c
index ba550eaa06fc..7b1871eb7a6f 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)) {
--
2.44.0
