[PATCH v8 10/11] irqchip/sifive-plic: Initialize the plic handler when cpu comes online

[Atish Patra]

Currently, plic threshold and priority are only initialized once in the
beginning. However, threshold can be set to disabled if cpu is marked
offline with cpu hotplug feature. This will not allow to change the
irq affinity to a cpu that just came online.

Add plic specific cpu hotplug callback and initialize the per cpu handler
when cpu comes online.

Signed-off-by: Atish Patra <atish.patra@xxxxxxx>
---
 drivers/irqchip/irq-sifive-plic.c | 34 ++++++++++++++++++++++++-------
 include/linux/cpuhotplug.h        |  1 +
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index 0aca5807a119..9b564b19f4bf 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -4,6 +4,7 @@
  * Copyright (C) 2018 Christoph Hellwig
  */
 #define pr_fmt(fmt) "plic: " fmt
+#include <linux/cpu.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/irq.h>
@@ -55,6 +56,8 @@
 #define     CONTEXT_THRESHOLD		0x00
 #define     CONTEXT_CLAIM		0x04
 
+#define	PLIC_DISABLE_THRESHOLD		0xffffffff
+
 static void __iomem *plic_regs;
 
 struct plic_handler {
@@ -208,6 +211,26 @@ static int plic_find_hart_id(struct device_node *node)
 	return -1;
 }
 
+static void plic_handler_init(struct plic_handler *handler, u32 threshold)
+{
+	irq_hw_number_t hwirq;
+
+	/* priority must be > threshold to trigger an interrupt */
+	writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
+	for (hwirq = 1; hwirq < plic_irqdomain->hwirq_max; hwirq++)
+		plic_toggle(handler, hwirq, 0);
+}
+
+static int plic_starting_cpu(unsigned int cpu)
+{
+	u32 threshold = 0;
+	struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
+
+	plic_handler_init(handler, threshold);
+
+	return 0;
+}
+
 static int __init plic_init(struct device_node *node,
 		struct device_node *parent)
 {
@@ -243,9 +266,7 @@ static int __init plic_init(struct device_node *node,
 	for (i = 0; i < nr_contexts; i++) {
 		struct of_phandle_args parent;
 		struct plic_handler *handler;
-		irq_hw_number_t hwirq;
 		int cpu, hartid;
-		u32 threshold = 0;
 
 		if (of_irq_parse_one(node, i, &parent)) {
 			pr_err("failed to parse parent for context %d.\n", i);
@@ -279,7 +300,7 @@ static int __init plic_init(struct device_node *node,
 		handler = per_cpu_ptr(&plic_handlers, cpu);
 		if (handler->present) {
 			pr_warn("handler already present for context %d.\n", i);
-			threshold = 0xffffffff;
+			plic_handler_init(handler, PLIC_DISABLE_THRESHOLD);
 			goto done;
 		}
 
@@ -291,13 +312,12 @@ static int __init plic_init(struct device_node *node,
 			plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;
 
 done:
-		/* priority must be > threshold to trigger an interrupt */
-		writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
-		for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
-			plic_toggle(handler, hwirq, 0);
 		nr_handlers++;
 	}
 
+	cpuhp_setup_state(CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
+				  "irqchip/sifive/plic:starting",
+				  plic_starting_cpu, NULL);
 	pr_info("mapped %d interrupts with %d handlers for %d contexts.\n",
 		nr_irqs, nr_handlers, nr_contexts);
 	set_handle_irq(plic_handle_irq);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index e51ee772b9f5..5360e03db08c 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -100,6 +100,7 @@ enum cpuhp_state {
 	CPUHP_AP_IRQ_ARMADA_XP_STARTING,
 	CPUHP_AP_IRQ_BCM2836_STARTING,
 	CPUHP_AP_IRQ_MIPS_GIC_STARTING,
+	CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
 	CPUHP_AP_ARM_MVEBU_COHERENCY,
 	CPUHP_AP_MICROCODE_LOADER,
 	CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
-- 
2.24.0