[PATCH 4/5] ARC: MCIP: Set an initial affinity value in idu_irq_map

From: Yuriy Kolerov
Date: Fri Oct 21 2016 - 18:17:08 EST

Originally an initial distribution mode (its value resides in Device Tree)
for each common interrupt is set in idu_irq_xlate. This leads to the
following problems. idu_irq_xlate may be called several times during parsing
of the Device Tree and it is semantically wrong to configure an initial
distribution mode here. Also a value of affinity (CPUs bitmap) is not saved
to irq_desc structure for the virq - later (after parsing of the DT) kernel
sees that affinity is not set and sets a default value of affinity (all
cores in round robin mode). As a result a value of affinity from Device
Tree is ignored.

To fix it I created a buffer for initial CPUs bitmaps from Device Tree.
In idu_irq_xlate those bitmaps are saved to the buffer. Then affinity
for virq is set manually in idu_irq_map. It works because idu_irq_xlate
is always called before idu_irq_map.

Despite the fact that it works I think that it must be rewritten to
eliminate usage of the buffer and move all logic to idu_irq_map but
I do not know how to do it correctly.

Signed-off-by: Yuriy Kolerov <yuriy.kolerov@xxxxxxxxxxxx>
arch/arc/kernel/mcip.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
index 51a218c..090f0a1 100644
--- a/arch/arc/kernel/mcip.c
+++ b/arch/arc/kernel/mcip.c
@@ -12,12 +12,15 @@
#include <linux/irq.h>
#include <linux/spinlock.h>
#include <linux/irqdomain.h>
+#include <linux/interrupt.h>
+#include <linux/cpumask.h>
#include <asm/irqflags-arcv2.h>
#include <asm/mcip.h>
#include <asm/setup.h>

static char smp_cpuinfo_buf[128];
static int idu_detected;
+static unsigned long idu_cirq_to_dest[CONFIG_ARC_NUMBER_OF_INTERRUPTS];

static DEFINE_RAW_SPINLOCK(mcip_lock);

@@ -232,9 +235,15 @@ static void idu_cascade_isr(struct irq_desc *desc)

static int idu_irq_map(struct irq_domain *d, unsigned int virq, irq_hw_number_t hwirq)
+ cpumask_t mask;
irq_set_chip_and_handler(virq, &idu_irq_chip, handle_level_irq);
irq_set_status_flags(virq, IRQ_MOVE_PCNTXT);

+ cpumask_clear(&mask);
+ cpumask_bits(&mask)[0] |= idu_cirq_to_dest[hwirq];
+ irq_set_affinity(virq, &mask);
return 0;

@@ -252,8 +261,7 @@ static int idu_irq_xlate(struct irq_domain *d, struct device_node *n,
if (distri == 0) {
/* 0 - Round Robin to all cpus, otherwise 1 bit per core */
raw_spin_lock_irqsave(&mcip_lock, flags);
- idu_set_dest(hwirq, BIT(num_online_cpus()) - 1);
- idu_set_mode(hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_RR);
+ idu_cirq_to_dest[hwirq] = BIT(num_online_cpus()) - 1;
raw_spin_unlock_irqrestore(&mcip_lock, flags);
} else {
@@ -267,8 +275,7 @@ static int idu_irq_xlate(struct irq_domain *d, struct device_node *n,
hwirq, cpu);

raw_spin_lock_irqsave(&mcip_lock, flags);
- idu_set_dest(hwirq, cpu);
- idu_set_mode(hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_DEST);
+ idu_cirq_to_dest[hwirq] = cpu;
raw_spin_unlock_irqrestore(&mcip_lock, flags);