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diff --git a/sys/dev/acpica/acpi_ec.c b/sys/dev/acpica/acpi_ec.c
--- a/sys/dev/acpica/acpi_ec.c
+++ b/sys/dev/acpica/acpi_ec.c
@@ -232,6 +232,7 @@
static int acpi_ec_probe(device_t dev);
static int acpi_ec_attach(device_t dev);
static int acpi_ec_suspend(device_t dev);
+static void acpi_ec_rearm_events(struct acpi_ec_softc *sc);
static int acpi_ec_resume(device_t dev);
static int acpi_ec_shutdown(device_t dev);
static int acpi_ec_read_method(device_t dev, u_int addr,
@@ -556,12 +557,49 @@
return (0);
}
+/*
+ * Some embedded controllers (e.g., the Lenovo H8 EC found in ThinkPad
+ * E14 laptops) stop reporting SCI events after a suspend/resume cycle:
+ * events are neither queued nor signalled until the host performs a
+ * burst enable/disable handshake. Perform that handshake to re-arm
+ * the EC event engine. It is part of the ACPI EC protocol and is
+ * harmless for ECs that do not need it.
+ */
+static void
+acpi_ec_rearm_events(struct acpi_ec_softc *sc)
+{
+ ACPI_STATUS status;
+
+ /*
+ * Waits are polled (ec_suspending is still TRUE), since the EC GPE
+ * is not yet re-enabled when this runs.
+ */
+ status = EcLock(sc);
+ if (ACPI_FAILURE(status))
+ return;
+ status = EcWaitEvent(sc, EC_EVENT_INPUT_BUFFER_EMPTY, 0);
+ if (ACPI_SUCCESS(status)) {
+ EC_SET_CSR(sc, EC_COMMAND_BURST_ENABLE);
+ (void)EcWaitEvent(sc, EC_EVENT_OUTPUT_BUFFER_FULL, sc->ec_gencount);
+ /* Consume the burst acknowledge byte, if any. */
+ if (EC_GET_CSR(sc) & EC_FLAG_OUTPUT_BUFFER)
+ (void)EC_GET_DATA(sc);
+
+ /* Leaving burst mode re-arms EC event reporting. */
+ status = EcWaitEvent(sc, EC_EVENT_INPUT_BUFFER_EMPTY, 0);
+ if (ACPI_SUCCESS(status))
+ EC_SET_CSR(sc, EC_COMMAND_BURST_DISABLE);
+ }
+ EcUnlock(sc);
+}
+
static int
acpi_ec_resume(device_t dev)
{
struct acpi_ec_softc *sc;
sc = device_get_softc(dev);
+ acpi_ec_rearm_events(sc);
sc->ec_suspending = FALSE;
return (0);
}

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