linux-kernel - [PATCH 3.2 33/94] ACPI / EC: Don't count a SCI interrupt as a false one

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Message-ID: <lsq.1407170912.755420222@decadent.org.uk>
Date:	Mon, 04 Aug 2014 17:48:32 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"Feng Tang" <feng.tang@...el.com>
Subject: [PATCH 3.2 33/94] ACPI / EC: Don't count a SCI interrupt as a
 false one

3.2.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Feng Tang <feng.tang@...el.com>

commit a3cd8d2789c2e265e09377f260e7d2ac9cec81bb upstream.

Currently when advance_transaction() is called in EC interrupt handler,
if there is nothing driver can do with the interrupt, it will be taken
as a false one.

But this is not always true, as there may be a SCI EC interrupt fired
during normal read/write operation, which should not be counted as a
false one. This patch fixes the problem.

Signed-off-by: Feng Tang <feng.tang@...el.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/acpi/ec.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -205,9 +205,13 @@ static void advance_transaction(struct a
 		t->done = true;
 	goto unlock;
 err:
-	/* false interrupt, state didn't change */
-	if (in_interrupt())
+	/*
+	 * If SCI bit is set, then don't think it's a false IRQ
+	 * otherwise will take a not handled IRQ as a false one.
+	 */
+	if (in_interrupt() && !(status & ACPI_EC_FLAG_SCI))
 		++t->irq_count;
+
 unlock:
 	spin_unlock_irqrestore(&ec->curr_lock, flags);
 }

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