[RFC PATCH 3/9] irqchip: GIC: Convert to EOImode == 1

[Marc Zyngier]

So far, GICv2 has been used in with EOImode == 0. The effect of this
mode is to perform the priority drop and the deactivation of the
interrupt at the same time.

While this works perfectly for Linux (we only have a single priority),
it causes issues when an interrupt is forwarded to a guest, and when
we want the guest to perform the EOI itself.

For this case, the GIC architecture provides EOImode == 1, where:
- A write to the EOI register drops the priority of the interrupt and leaves
it active. Other interrupts at the same priority level can now be taken,
but the active interrupt cannot be taken again
- A write to the DIR marks the interrupt as inactive, meaning it can
now be taken again.

We only enable this feature when booted in HYP mode. Also, as most device
trees are broken (they report the CPU interface size to be 4kB, while
the GICv2 CPU interface size is 8kB), output a warning if we're booted
in HYP mode, and disable the feature.

Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
 drivers/irqchip/irq-gic.c       | 61 +++++++++++++++++++++++++++++++++++++----
 include/linux/irqchip/arm-gic.h |  4 +++
 2 files changed, 59 insertions(+), 6 deletions(-)

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index 508b815..9295bf2 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -45,6 +45,7 @@
 #include <asm/irq.h>
 #include <asm/exception.h>
 #include <asm/smp_plat.h>
+#include <asm/virt.h>
 
 #include "irq-gic-common.h"
 #include "irqchip.h"
@@ -94,6 +95,10 @@ struct irq_chip gic_arch_extn = {
 	.irq_set_wake	= NULL,
 };
 
+static struct irq_chip *gic_chip;
+
+static bool supports_deactivate = false;
+
 #ifndef MAX_GIC_NR
 #define MAX_GIC_NR	1
 #endif
@@ -185,6 +190,12 @@ static void gic_eoi_irq(struct irq_data *d)
 	writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI);
 }
 
+static void gic_eoi_dir_irq(struct irq_data *d)
+{
+	gic_eoi_irq(d);
+	writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_DEACTIVATE);
+}
+
 static int gic_set_type(struct irq_data *d, unsigned int type)
 {
 	void __iomem *base = gic_dist_base(d);
@@ -277,6 +288,7 @@ static void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
 		}
 		if (irqnr < 16) {
 			writel_relaxed(irqstat, cpu_base + GIC_CPU_EOI);
+			writel_relaxed(irqstat, cpu_base + GIC_CPU_DEACTIVATE);
 #ifdef CONFIG_SMP
 			handle_IPI(irqnr, regs);
 #endif
@@ -313,7 +325,7 @@ static void gic_handle_cascade_irq(unsigned int irq, struct irq_desc *desc)
 	chained_irq_exit(chip, desc);
 }
 
-static struct irq_chip gic_chip = {
+static struct irq_chip gicv1_chip = {
 	.name			= "GIC",
 	.irq_mask		= gic_mask_irq,
 	.irq_unmask		= gic_unmask_irq,
@@ -326,6 +338,19 @@ static struct irq_chip gic_chip = {
 	.irq_set_wake		= gic_set_wake,
 };
 
+static struct irq_chip gicv2_chip = {
+	.name			= "GIC",
+	.irq_mask		= gic_mask_irq,
+	.irq_unmask		= gic_unmask_irq,
+	.irq_eoi		= gic_eoi_dir_irq,
+	.irq_set_type		= gic_set_type,
+	.irq_retrigger		= gic_retrigger,
+#ifdef CONFIG_SMP
+	.irq_set_affinity	= gic_set_affinity,
+#endif
+	.irq_set_wake		= gic_set_wake,
+};
+
 void __init gic_cascade_irq(unsigned int gic_nr, unsigned int irq)
 {
 	if (gic_nr >= MAX_GIC_NR)
@@ -377,6 +402,16 @@ static void __init gic_dist_init(struct gic_chip_data *gic)
 	writel_relaxed(1, base + GIC_DIST_CTRL);
 }
 
+static void gic_cpu_if_up(void)
+{
+	void __iomem *cpu_base = gic_data_cpu_base(&gic_data[0]);
+	u32 val = 0;
+
+	if (supports_deactivate)
+		val = GIC_CPU_CTRL_EOImodeNS;
+	writel_relaxed(val | 1, cpu_base + GIC_CPU_CTRL);
+}
+
 static void gic_cpu_init(struct gic_chip_data *gic)
 {
 	void __iomem *dist_base = gic_data_dist_base(gic);
@@ -402,7 +437,7 @@ static void gic_cpu_init(struct gic_chip_data *gic)
 	gic_cpu_config(dist_base, NULL);
 
 	writel_relaxed(0xf0, base + GIC_CPU_PRIMASK);
-	writel_relaxed(1, base + GIC_CPU_CTRL);
+	gic_cpu_if_up();
 }
 
 void gic_cpu_if_down(void)
@@ -543,7 +578,7 @@ static void gic_cpu_restore(unsigned int gic_nr)
 		writel_relaxed(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4);
 
 	writel_relaxed(0xf0, cpu_base + GIC_CPU_PRIMASK);
-	writel_relaxed(1, cpu_base + GIC_CPU_CTRL);
+	gic_cpu_if_up();
 }
 
 static int gic_notifier(struct notifier_block *self, unsigned long cmd,	void *v)
@@ -770,11 +805,11 @@ static int gic_irq_domain_map(struct irq_domain *d, unsigned int irq,
 {
 	if (hw < 32) {
 		irq_set_percpu_devid(irq);
-		irq_set_chip_and_handler(irq, &gic_chip,
+		irq_set_chip_and_handler(irq, gic_chip,
 					 handle_percpu_devid_irq);
 		set_irq_flags(irq, IRQF_VALID | IRQF_NOAUTOEN);
 	} else {
-		irq_set_chip_and_handler(irq, &gic_chip,
+		irq_set_chip_and_handler(irq, gic_chip,
 					 handle_fasteoi_irq);
 		set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);
 
@@ -951,6 +986,11 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
 
 	gic_irqs -= hwirq_base; /* calculate # of irqs to allocate */
 
+	if (!supports_deactivate)
+		gic_chip = &gicv1_chip;
+	else
+		gic_chip = &gicv2_chip;
+
 	if (of_property_read_u32(node, "arm,routable-irqs",
 				 &nr_routable_irqs)) {
 		irq_base = irq_alloc_descs(irq_start, 16, gic_irqs,
@@ -980,7 +1020,7 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
 		set_handle_irq(gic_handle_irq);
 	}
 
-	gic_chip.flags |= gic_arch_extn.flags;
+	gic_chip->flags |= gic_arch_extn.flags;
 	gic_dist_init(gic);
 	gic_cpu_init(gic);
 	gic_pm_init(gic);
@@ -994,6 +1034,7 @@ gic_of_init(struct device_node *node, struct device_node *parent)
 {
 	void __iomem *cpu_base;
 	void __iomem *dist_base;
+	struct resource cpu_res;
 	u32 percpu_offset;
 	int irq;
 
@@ -1006,6 +1047,14 @@ gic_of_init(struct device_node *node, struct device_node *parent)
 	cpu_base = of_iomap(node, 1);
 	WARN(!cpu_base, "unable to map gic cpu registers\n");
 
+	of_address_to_resource(node, 1, &cpu_res);
+	if (is_hyp_mode_available()) {
+		if (resource_size(&cpu_res) >= SZ_8K)
+			supports_deactivate = true;
+		else
+			pr_warn("GIC: CPU interface size is %x, DT is probably wrong\n", (int)resource_size(&cpu_res));
+	}
+
 	if (of_property_read_u32(node, "cpu-offset", &percpu_offset))
 		percpu_offset = 0;
 
diff --git a/include/linux/irqchip/arm-gic.h b/include/linux/irqchip/arm-gic.h
index 45e2d8c..ffe3911 100644
--- a/include/linux/irqchip/arm-gic.h
+++ b/include/linux/irqchip/arm-gic.h
@@ -21,6 +21,10 @@
 #define GIC_CPU_ACTIVEPRIO		0xd0
 #define GIC_CPU_IDENT			0xfc
 
+#define GIC_CPU_DEACTIVATE		0x1000
+
+#define GIC_CPU_CTRL_EOImodeNS		(1 << 9)
+
 #define GICC_IAR_INT_ID_MASK		0x3ff
 
 #define GIC_DIST_CTRL			0x000
-- 
1.8.3.4

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