On multiple devices I work on, we noticed that
/sys/firmware/acpi/interrupts/sci_not is non-zero and keeps increasing
over time.
It turns out that there is a race condition between servicing a GPE
interrupt and handling task driven transactions.
If a GPE interrupt is received at the same time ec_poll() is running,
the advance_transaction() clears the GPE flag and the interrupt is not
serviced as acpi_ev_detect_gpe() relies on the GPE flag to call the
handler. As a result, `sci_not' is increased.
Signed-off-by: Jeremy Compostella <jeremy.compostella@xxxxxxxxx>
---
drivers/acpi/ec.c | 31 ++++++++++++++++---------------
1 file changed, 16 insertions(+), 15 deletions(-)
diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 928899ab9502..8569f55e55b6 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -662,21 +662,6 @@ static void advance_transaction(struct acpi_ec *ec, bool interrupt)
ec_dbg_stm("%s (%d)", interrupt ? "IRQ" : "TASK", smp_processor_id());
- /*
- * Clear GPE_STS upfront to allow subsequent hardware GPE_STS 0->1
- * changes to always trigger a GPE interrupt.
- *
- * GPE STS is a W1C register, which means:
- *
- * 1. Software can clear it without worrying about clearing the other
- * GPEs' STS bits when the hardware sets them in parallel.
- *
- * 2. As long as software can ensure only clearing it when it is set,
- * hardware won't set it in parallel.
- */
- if (ec->gpe >= 0 && acpi_ec_gpe_status_set(ec))
- acpi_clear_gpe(NULL, ec->gpe);
-
status = acpi_ec_read_status(ec);
/*
@@ -1287,6 +1272,22 @@ static void acpi_ec_handle_interrupt(struct acpi_ec *ec)
unsigned long flags;
spin_lock_irqsave(&ec->lock, flags);
+
+ /*
+ * Clear GPE_STS upfront to allow subsequent hardware GPE_STS 0->1
+ * changes to always trigger a GPE interrupt.
+ *
+ * GPE STS is a W1C register, which means:
+ *
+ * 1. Software can clear it without worrying about clearing the other
+ * GPEs' STS bits when the hardware sets them in parallel.
+ *
+ * 2. As long as software can ensure only clearing it when it is set,
+ * hardware won't set it in parallel.
+ */
+ if (ec->gpe >= 0 && acpi_ec_gpe_status_set(ec))
+ acpi_clear_gpe(NULL, ec->gpe);
+
advance_transaction(ec, true);
spin_unlock_irqrestore(&ec->lock, flags);
}
--
2.40.1
