xen/riscv: introduce intc_init() and helpers

Introduce intc_init() to initialize the interrupt controller using the
registered hardware ops.
Also add intc_route_irq_to_xen() to route IRQs to Xen, with support for
setting IRQ type and priority via new internal helpers intc_set_irq_type()
and intc_set_irq_priority().

Call intc_init() to do basic initialization steps for APLIC and IMSIC.

Co-developed-by: Romain Caritey <Romain.Caritey@microchip.com>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/riscv/include/asm/intc.h

@@ -43,4 +43,8 @@ void intc_preinit(void);
 
 void register_intc_ops(const struct intc_hw_operations *ops);
 
+void intc_init(void);
+
+void intc_route_irq_to_xen(struct irq_desc *desc, unsigned int priority);
+
 #endif /* ASM__RISCV__INTERRUPT_CONTOLLER_H */

xen/arch/riscv/intc.c

@@ -1,9 +1,12 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
 #include <xen/acpi.h>
+#include <xen/bug.h>
 #include <xen/device_tree.h>
 #include <xen/init.h>
+#include <xen/irq.h>
 #include <xen/lib.h>
+#include <xen/spinlock.h>
 
 #include <asm/intc.h>
 
@@ -21,3 +24,41 @@ void __init intc_preinit(void)
     else
         panic("ACPI interrupt controller preinit() isn't implemented\n");
 }
+
+void __init intc_init(void)
+{
+    if ( intc_hw_ops->init() )
+        panic("Failed to initialize the interrupt controller drivers\n");
+}
+
+/* desc->irq needs to be disabled before calling this function */
+static void intc_set_irq_type(struct irq_desc *desc, unsigned int type)
+{
+    ASSERT(desc->status & IRQ_DISABLED);
+    ASSERT(spin_is_locked(&desc->lock));
+    ASSERT(type != IRQ_TYPE_INVALID);
+
+    if ( intc_hw_ops->set_irq_type )
+        intc_hw_ops->set_irq_type(desc, type);
+}
+
+static void intc_set_irq_priority(struct irq_desc *desc, unsigned int priority)
+{
+    ASSERT(spin_is_locked(&desc->lock));
+
+    if ( intc_hw_ops->set_irq_priority )
+        intc_hw_ops->set_irq_priority(desc, priority);
+}
+
+void intc_route_irq_to_xen(struct irq_desc *desc, unsigned int priority)
+{
+    ASSERT(desc->status & IRQ_DISABLED);
+    ASSERT(spin_is_locked(&desc->lock));
+    /* Can't route interrupts that don't exist */
+    ASSERT(intc_hw_ops && desc->irq < intc_hw_ops->info->num_irqs);
+
+    desc->handler = intc_hw_ops->host_irq_type;
+
+    intc_set_irq_type(desc, desc->arch.type);
+    intc_set_irq_priority(desc, priority);
+}

xen/arch/riscv/setup.c

@@ -134,6 +134,8 @@ void __init noreturn start_xen(unsigned long bootcpu_id,
 
     intc_preinit();
 
+    intc_init();
+
     printk("All set up\n");
 
     machine_halt();