linux-kernel - [PATCH 3.19.y-ckt 102/196] irqchip/gic-v3-its: Fix double ICC

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Message-Id: <1457483454-30115-103-git-send-email-kamal@canonical.com>
Date:	Tue,  8 Mar 2016 16:29:20 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Ashok Kumar <ashoks@...adcom.com>,
	Marc Zyngier <marc.zyngier@....com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 102/196] irqchip/gic-v3-its: Fix double ICC_EOIR write for LPI in EOImode==1

3.19.8-ckt16 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Ashok Kumar <ashoks@...adcom.com>

commit 004fa08d7aba2a13974446bf212a48c0b3b0d9fd upstream.

When the GIC is using EOImode==1, the EOI is done immediately,
leaving the deactivation to be performed when the EOI was
previously done.

Unfortunately, the ITS is not aware of the EOImode at all, and
blindly EOIs the interrupt again. On most systems, this is ignored
(despite being a programming error), but some others do raise a
SError exception as there is no priority drop to perform for this
interrupt.

The fix is to stop trying to be clever, and always call into the
underlying GIC to perform the right access, irrespective of the
more we're in.

[Marc: Reworked commit message]

Fixes: 0b996fd35957a ("irqchip/GICv3: Convert to EOImode == 1")
Acked-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Ashok Kumar <ashoks@...adcom.com>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/irqchip/irq-gic-v3-its.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index d8996bd..0b8e68e 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -564,11 +564,6 @@ static void its_unmask_irq(struct irq_data *d)
 	lpi_set_config(d, true);
 }
 
-static void its_eoi_irq(struct irq_data *d)
-{
-	gic_write_eoir(d->hwirq);
-}
-
 static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
 			    bool force)
 {
@@ -605,7 +600,7 @@ static struct irq_chip its_irq_chip = {
 	.name			= "ITS",
 	.irq_mask		= its_mask_irq,
 	.irq_unmask		= its_unmask_irq,
-	.irq_eoi		= its_eoi_irq,
+	.irq_eoi		= irq_chip_eoi_parent,
 	.irq_set_affinity	= its_set_affinity,
 	.irq_compose_msi_msg	= its_irq_compose_msi_msg,
 };
-- 
2.7.0