[PATCH] ARCv2: MCIP: Deprecate setting of affinity in Device Tree

[Yuriy Kolerov]

Ignore value of interrupt distribution mode for common interrupts in
IDU since setting of affinity using value from Device Tree is deprecated
in ARC. Originally it is done in idu_irq_xlate() function and it is
semantically wrong and does not guaranty that an affinity value will be
set properly.

However it is necessary to set a default affinity value manually for all
common interrupts since initially all of them are disabled by IDU (a
CPU mask for common interrupts is set to 0 after CPU reset) and in
some cases the kernel cannot do it itself after initialization of
endpoint devices (e.g. when IRQ chip below of IDU does not support
setting of affinity and it cannot propagate an affinity value to IDU).

By default send all common interrupts to the first online CPU.
Usually it is a boot CPU. If the kernel is built without support
of SMP then idu_irq_set_affinity() must be called manually since
irq_set_affinity() does nothing in this case.

Signed-off-by: Yuriy Kolerov <yuriy.kolerov@xxxxxxxxxxxx>
---
 .../interrupt-controller/snps,archs-idu-intc.txt   |  3 ++
 arch/arc/kernel/mcip.c                             | 51 +++++++++-------------
 2 files changed, 24 insertions(+), 30 deletions(-)

diff --git a/Documentation/devicetree/bindings/interrupt-controller/snps,archs-idu-intc.txt b/Documentation/devicetree/bindings/interrupt-controller/snps,archs-idu-intc.txt
index 0dcb7c7..0607bab 100644
--- a/Documentation/devicetree/bindings/interrupt-controller/snps,archs-idu-intc.txt
+++ b/Documentation/devicetree/bindings/interrupt-controller/snps,archs-idu-intc.txt
@@ -15,6 +15,9 @@ Properties:
   Second cell specifies the irq distribution mode to cores
      0=Round Robin; 1=cpu0, 2=cpu1, 4=cpu2, 8=cpu3
 
+  The second cell in interrupts property is deprecated and ignored. All common
+  interrupts are sent to the boot CPU core by default.
+
   intc accessed via the special ARC AUX register interface, hence "reg" property
   is not specified.
 
diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
index 6d90e4b..f36b8d7 100644
--- a/arch/arc/kernel/mcip.c
+++ b/arch/arc/kernel/mcip.c
@@ -174,7 +174,6 @@ static void idu_irq_unmask(struct irq_data *data)
 	raw_spin_unlock_irqrestore(&mcip_lock, flags);
 }
 
-#ifdef CONFIG_SMP
 static int
 idu_irq_set_affinity(struct irq_data *data, const struct cpumask *cpumask,
 		     bool force)
@@ -204,7 +203,6 @@ idu_irq_set_affinity(struct irq_data *data, const struct cpumask *cpumask,
 
 	return IRQ_SET_MASK_OK;
 }
-#endif
 
 static struct irq_chip idu_irq_chip = {
 	.name			= "MCIP IDU Intc",
@@ -228,9 +226,24 @@ 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 affinity;
+
 	irq_set_chip_and_handler(virq, &idu_irq_chip, handle_level_irq);
 	irq_set_status_flags(virq, IRQ_MOVE_PCNTXT);
 
+	/* By default send all common interrupts to the first online CPU.
+	 * Usually it is a boot CPU. If the kernel is built without support
+	 * of SMP then idu_irq_set_affinity() must be called manually since
+	 * irq_set_affinity() does nothing in this case.
+	 */
+	cpumask_copy(&affinity, cpumask_of(cpumask_first(cpu_online_mask)));
+
+#ifdef CONFIG_SMP
+	irq_set_affinity(virq, &affinity);
+#else
+	idu_irq_set_affinity(irq_get_irq_data(virq), &affinity, false);
+#endif
+
 	return 0;
 }
 
@@ -238,36 +251,14 @@ static int idu_irq_xlate(struct irq_domain *d, struct device_node *n,
 			 const u32 *intspec, unsigned int intsize,
 			 irq_hw_number_t *out_hwirq, unsigned int *out_type)
 {
-	irq_hw_number_t hwirq = *out_hwirq = intspec[0];
-	int distri = intspec[1];
-	unsigned long flags;
-
+	/*
+	 * Ignore value of interrupt distribution mode for common interrupts in
+	 * IDU which resides in intspec[1] since setting an affinity using value
+	 * from Device Tree is deprecated in ARC.
+	 */
+	*out_hwirq = intspec[0];
 	*out_type = IRQ_TYPE_NONE;
 
-	/* XXX: validate distribution scheme again online cpu mask */
-	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);
-		raw_spin_unlock_irqrestore(&mcip_lock, flags);
-	} else {
-		/*
-		 * DEST based distribution for Level Triggered intr can only
-		 * have 1 CPU, so generalize it to always contain 1 cpu
-		 */
-		int cpu = ffs(distri);
-
-		if (cpu != fls(distri))
-			pr_warn("IDU irq %lx distri mode set to cpu %x\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);
-		raw_spin_unlock_irqrestore(&mcip_lock, flags);
-	}
-
 	return 0;
 }
 
-- 
2.7.4