[3.11.y.z extended stable] Patch "irqchip: gic: Fix core ID calculation when topology is read from DT" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    irqchip: gic: Fix core ID calculation when topology is read from DT

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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>From 70554d7c0e007420b9aa097c2f7510ef519c1542 Mon Sep 17 00:00:00 2001
From: Tomasz Figa <t.figa at samsung.com>
Date: Thu, 17 Jul 2014 17:23:44 +0200
Subject: irqchip: gic: Fix core ID calculation when topology is read from DT

commit 29e697b11853d3f83b1864ae385abdad4aa2c361 upstream.

Certain GIC implementation, namely those found on earlier, single
cluster, Exynos SoCs, have registers mapped without per-CPU banking,
which means that the driver needs to use different offset for each CPU.

Currently the driver calculates the offset by multiplying value returned
by cpu_logical_map() by CPU offset parsed from DT. This is correct when
CPU topology is not specified in DT and aforementioned function returns
core ID alone. However when DT contains CPU topology, the function
changes to return cluster ID as well, which is non-zero on mentioned
SoCs and so breaks the calculation in GIC driver.

This patch fixes this by masking out cluster ID in CPU offset
calculation so that only core ID is considered. Multi-cluster Exynos
SoCs already have banked GIC implementations, so this simple fix should
be enough.

Reported-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
Reported-by: Bartlomiej Zolnierkiewicz <b.zolnierkie at samsung.com>
Signed-off-by: Tomasz Figa <t.figa at samsung.com>
Fixes: db0d4db22a78d ("ARM: gic: allow GIC to support non-banked setups")
Link: https://lkml.kernel.org/r/1405610624-18722-1-git-send-email-t.figa@samsung.com
Signed-off-by: Jason Cooper <jason at lakedaemon.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/irqchip/irq-gic.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index 97fd4bf56f3e..4e2347ad869d 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -42,6 +42,7 @@
 #include <linux/irqchip/chained_irq.h>
 #include <linux/irqchip/arm-gic.h>

+#include <asm/cputype.h>
 #include <asm/irq.h>
 #include <asm/exception.h>
 #include <asm/smp_plat.h>
@@ -754,7 +755,9 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
 		}

 		for_each_possible_cpu(cpu) {
-			unsigned long offset = percpu_offset * cpu_logical_map(cpu);
+			u32 mpidr = cpu_logical_map(cpu);
+			u32 core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
+			unsigned long offset = percpu_offset * core_id;
 			*per_cpu_ptr(gic->dist_base.percpu_base, cpu) = dist_base + offset;
 			*per_cpu_ptr(gic->cpu_base.percpu_base, cpu) = cpu_base + offset;
 		}
--
1.9.1