[RFC 06/12] riscv: Allow requesting irq as pseudo NMI

[Xu Lu]

This commit implements pseudo NMI callbacks for riscv_intc_irq chip. We
use an immediate macro to denote NMIs of each cpu. Each bit of it
represents an irq. Bit 1 means corresponding irq is registered as NMI
while bit 0 means not.

Signed-off-by: Xu Lu <luxu.kernel@xxxxxxxxxxxxx>
Signed-off-by: Hangjing Li <lihangjing@xxxxxxxxxxxxx>
Reviewed-by: Liang Deng <dengliang.1214@xxxxxxxxxxxxx>
Reviewed-by: Yu Li <liyu.yukiteru@xxxxxxxxxxxxx>
---
 arch/riscv/include/asm/irqflags.h | 17 ++++++++++++++
 drivers/irqchip/irq-riscv-intc.c  | 38 +++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/arch/riscv/include/asm/irqflags.h b/arch/riscv/include/asm/irqflags.h
index 60c19f8b57f0..9700a17a003a 100644
--- a/arch/riscv/include/asm/irqflags.h
+++ b/arch/riscv/include/asm/irqflags.h
@@ -12,6 +12,23 @@
 
 #ifdef CONFIG_RISCV_PSEUDO_NMI
 
+#define __ALLOWED_NMI_MASK			0
+#define ALLOWED_NMI_MASK			(__ALLOWED_NMI_MASK & irqs_enabled_ie)
+
+static inline bool nmi_allowed(int irq)
+{
+	return (BIT(irq) & ALLOWED_NMI_MASK);
+}
+
+static inline bool is_nmi(int irq)
+{
+	return (BIT(irq) & ALLOWED_NMI_MASK);
+}
+
+static inline void set_nmi(int irq) {}
+
+static inline void unset_nmi(int irq) {}
+
 static inline void local_irq_switch_on(void)
 {
 	csr_set(CSR_STATUS, SR_IE);
diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
index 7fad1ba37e5c..83a0a744fce6 100644
--- a/drivers/irqchip/irq-riscv-intc.c
+++ b/drivers/irqchip/irq-riscv-intc.c
@@ -67,11 +67,49 @@ static void riscv_intc_irq_eoi(struct irq_data *d)
 	 */
 }
 
+#ifdef CONFIG_RISCV_PSEUDO_NMI
+
+static int riscv_intc_irq_nmi_setup(struct irq_data *d)
+{
+	unsigned int hwirq = d->hwirq;
+	struct irq_desc *desc = irq_to_desc(d->irq);
+
+	if (WARN_ON((hwirq >= BITS_PER_LONG) || !nmi_allowed(hwirq)))
+		return -EINVAL;
+
+	desc->handle_irq = handle_percpu_devid_fasteoi_nmi;
+	set_nmi(hwirq);
+
+	return 0;
+}
+
+static void riscv_intc_irq_nmi_teardown(struct irq_data *d)
+{
+	unsigned int hwirq = d->hwirq;
+	struct irq_desc *desc = irq_to_desc(d->irq);
+
+	if (WARN_ON(hwirq >= BITS_PER_LONG))
+		return;
+
+	if (WARN_ON(!is_nmi(hwirq)))
+		return;
+
+	desc->handle_irq = handle_percpu_devid_irq;
+	unset_nmi(hwirq);
+}
+
+#endif /* CONFIG_RISCV_PSEUDO_NMI */
+
 static struct irq_chip riscv_intc_chip = {
 	.name = "RISC-V INTC",
 	.irq_mask = riscv_intc_irq_mask,
 	.irq_unmask = riscv_intc_irq_unmask,
 	.irq_eoi = riscv_intc_irq_eoi,
+#ifdef CONFIG_RISCV_PSEUDO_NMI
+	.irq_nmi_setup = riscv_intc_irq_nmi_setup,
+	.irq_nmi_teardown = riscv_intc_irq_nmi_teardown,
+	.flags = IRQCHIP_SUPPORTS_NMI,
+#endif
 };
 
 static int riscv_intc_domain_map(struct irq_domain *d, unsigned int irq,
-- 
2.20.1