[PATCH v4 1/2] ARC: IRQ: Do not use hwirq as virq and vice versa

Yuriy Kolerov yuriy.kolerov at synopsys.com
Mon Nov 7 23:08:31 PST 2016

At first smp_ipi_irq_setup() takes a cpu number and a hwirq number for
the per core local interrupt line in the root interrupt controller and
registers an appropriate IPI handler per cpu. However this function tries
to bind a handler to the hwirq as virtual IRQ number and it is a wrong
behavior. It is necessary to find a mapping of hwirq in the root IRQ
domain to the actual virq using irq_find_mapping(). Also a declaration
of smp_ipi_irq_setup() is corrected to denote that this function takes
a hardware IRQ number but not a virtual IRQ number.

Also there is one more problem related to usage of IRQ numbers. Multicore
ARC configurations use IDU (Interrupt Distribution Unit) for distributing
of common interrupts. In fact IDU is a interrupt controller on top of
main per core interrupt controller.

All common IRQs are physically and linearly mapped to per core
interrupts. E.g. <0, 1, 2, 3> common IDU interrupts may be mapped to per
core <24, 25, 26, 27> interrupts. An initialization code of IDU
controller (idu_of_init()) creates mappings for all parent interrupts
<24, 25, ...> and sets a chained IDU handler for them. In the same
time idu_of_init() must save the first met parent hwirq (idu_first_irq)
thus in future it is possible to figure out what common hwirq has come
by subtracting of idu_first_irq from the current parent hwirq (see

The problem is that idu_of_init() and idu_cascade_isr() use parent virtual
IRQs as hardware IRQs and perform all the above-described manipulations
on virtual IRQs. But it is wrong and hardware IRQs must be used instead.

Signed-off-by: Yuriy Kolerov <yuriy.kolerov at synopsys.com>
 arch/arc/include/asm/smp.h |  4 ++--
 arch/arc/kernel/mcip.c     | 20 +++++++++-----------
 arch/arc/kernel/smp.c      | 13 +++++++++----
 3 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/arch/arc/include/asm/smp.h b/arch/arc/include/asm/smp.h
index 89fdd1b..0861007 100644
--- a/arch/arc/include/asm/smp.h
+++ b/arch/arc/include/asm/smp.h
@@ -37,9 +37,9 @@ extern const char *arc_platform_smp_cpuinfo(void);
  * API expected BY platform smp code (FROM arch smp code)
  * smp_ipi_irq_setup:
- *	Takes @cpu and @irq to which the arch-common ISR is hooked up
+ *	Takes @cpu and @hwirq to which the arch-common ISR is hooked up
-extern int smp_ipi_irq_setup(int cpu, int irq);
+extern int smp_ipi_irq_setup(int cpu, irq_hw_number_t hwirq);
  * struct plat_smp_ops	- SMP callbacks provided by platform to ARC SMP
diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
index 72f9179..4f4f04b 100644
--- a/arch/arc/kernel/mcip.c
+++ b/arch/arc/kernel/mcip.c
@@ -219,16 +219,14 @@ static struct irq_chip idu_irq_chip = {
-static int idu_first_irq;
+static irq_hw_number_t idu_first_hwirq;
 static void idu_cascade_isr(struct irq_desc *desc)
-	struct irq_domain *domain = irq_desc_get_handler_data(desc);
-	unsigned int core_irq = irq_desc_get_irq(desc);
-	unsigned int idu_irq;
-	idu_irq = core_irq - idu_first_irq;
-	generic_handle_irq(irq_find_mapping(domain, idu_irq));
+	struct irq_domain *idu_domain = irq_desc_get_handler_data(desc);
+	irq_hw_number_t core_hwirq = irqd_to_hwirq(irq_desc_get_irq_data(desc));
+	irq_hw_number_t idu_hwirq = core_hwirq - idu_first_hwirq;
+	generic_handle_irq(irq_find_mapping(idu_domain, idu_hwirq));
 static int idu_irq_map(struct irq_domain *d, unsigned int virq, irq_hw_number_t hwirq)
@@ -294,7 +292,7 @@ idu_of_init(struct device_node *intc, struct device_node *parent)
 	struct irq_domain *domain;
 	/* Read IDU BCR to confirm nr_irqs */
 	int nr_irqs = of_irq_count(intc);
-	int i, irq;
+	int i, virq;
 	if (!idu_detected)
 		panic("IDU not detected, but DeviceTree using it");
@@ -312,11 +310,11 @@ idu_of_init(struct device_node *intc, struct device_node *parent)
 		 * however we need it to get the parent virq and set IDU handler
 		 * as first level isr
-		irq = irq_of_parse_and_map(intc, i);
+		virq = irq_of_parse_and_map(intc, i);
 		if (!i)
-			idu_first_irq = irq;
+			idu_first_hwirq = irqd_to_hwirq(irq_get_irq_data(virq));
-		irq_set_chained_handler_and_data(irq, idu_cascade_isr, domain);
+		irq_set_chained_handler_and_data(virq, idu_cascade_isr, domain);
 	__mcip_cmd(CMD_IDU_ENABLE, 0);
diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c
index f183cc6..692ca51 100644
--- a/arch/arc/kernel/smp.c
+++ b/arch/arc/kernel/smp.c
@@ -22,6 +22,7 @@
 #include <linux/atomic.h>
 #include <linux/cpumask.h>
 #include <linux/reboot.h>
+#include <linux/irqdomain.h>
 #include <asm/processor.h>
 #include <asm/setup.h>
 #include <asm/mach_desc.h>
@@ -351,20 +352,24 @@ irqreturn_t do_IPI(int irq, void *dev_id)
 static DEFINE_PER_CPU(int, ipi_dev);
-int smp_ipi_irq_setup(int cpu, int irq)
+int smp_ipi_irq_setup(int cpu, irq_hw_number_t hwirq)
 	int *dev = per_cpu_ptr(&ipi_dev, cpu);
+	unsigned int virq = irq_find_mapping(NULL, hwirq);
+	if (!virq)
+		panic("Cannot find virq for root domain and hwirq=%lu", hwirq);
 	/* Boot cpu calls request, all call enable */
 	if (!cpu) {
 		int rc;
-		rc = request_percpu_irq(irq, do_IPI, "IPI Interrupt", dev);
+		rc = request_percpu_irq(virq, do_IPI, "IPI Interrupt", dev);
 		if (rc)
-			panic("Percpu IRQ request failed for %d\n", irq);
+			panic("Percpu IRQ request failed for %u\n", virq);
-	enable_percpu_irq(irq, 0);
+	enable_percpu_irq(virq, 0);
 	return 0;

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