target/nios2: Move IIC code into CPU object proper

The Nios2 architecture supports two different interrupt controller
options:

 * The IIC (Internal Interrupt Controller) is part of the CPU itself;
   it has 32 IRQ input lines and no NMI support.  Interrupt status is
   queried and controlled via the CPU's ipending and istatus
   registers.

 * The EIC (External Interrupt Controller) interface allows the CPU
   to connect to an external interrupt controller.  The interface
   allows the interrupt controller to present a packet of information
   containing:
    - handler address
    - interrupt level
    - register set
    - NMI mode

QEMU does not model an EIC currently.  We do model the IIC, but its
implementation is split across code in hw/nios2/cpu_pic.c and
hw/intc/nios2_iic.c.  The code in those two files has no state of its
own -- the IIC state is in the Nios2CPU state struct.

Because CPU objects now inherit (indirectly) from TYPE_DEVICE, they
can have GPIO input lines themselves, so we can implement the IIC
directly in the CPU object the same way that real hardware does.

Create named "IRQ" GPIO inputs to the Nios2 CPU object, and make the
only user of the IIC wire up directly to those instead.

Note that the old code had an "NMI" concept which was entirely unused
and also as far as I can see not architecturally correct, since only
the EIC has a concept of an NMI.

This fixes a Coverity-reported trivial memory leak of the IRQ array
allocated in nios2_cpu_pic_init().

Fixes: Coverity CID 1421916
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20201129174022.26530-2-peter.maydell@linaro.org
Reviewed-by: Wentong Wu <wentong.wu@intel.com>
Tested-by: Wentong Wu <wentong.wu@intel.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/target/nios2/cpu.c b/target/nios2/cpu.c
index 8f7011fcb9..52ebda89ca 100644
--- a/target/nios2/cpu.c
+++ b/target/nios2/cpu.c
@@ -64,6 +64,27 @@ static void nios2_cpu_reset(DeviceState *dev)
 #endif
 }
 
+#ifndef CONFIG_USER_ONLY
+static void nios2_cpu_set_irq(void *opaque, int irq, int level)
+{
+    Nios2CPU *cpu = opaque;
+    CPUNios2State *env = &cpu->env;
+    CPUState *cs = CPU(cpu);
+
+    env->regs[CR_IPENDING] &= ~(1 << irq);
+    env->regs[CR_IPENDING] |= !!level << irq;
+
+    env->irq_pending = env->regs[CR_IPENDING] & env->regs[CR_IENABLE];
+
+    if (env->irq_pending && (env->regs[CR_STATUS] & CR_STATUS_PIE)) {
+        env->irq_pending = 0;
+        cpu_interrupt(cs, CPU_INTERRUPT_HARD);
+    } else if (!env->irq_pending) {
+        cpu_reset_interrupt(cs, CPU_INTERRUPT_HARD);
+    }
+}
+#endif
+
 static void nios2_cpu_initfn(Object *obj)
 {
     Nios2CPU *cpu = NIOS2_CPU(obj);
@@ -72,6 +93,15 @@ static void nios2_cpu_initfn(Object *obj)
 
 #if !defined(CONFIG_USER_ONLY)
     mmu_init(&cpu->env);
+
+    /*
+     * These interrupt lines model the IIC (internal interrupt
+     * controller). QEMU does not currently support the EIC
+     * (external interrupt controller) -- if we did it would be
+     * a separate device in hw/intc with a custom interface to
+     * the CPU, and boards using it would not wire up these IRQ lines.
+     */
+    qdev_init_gpio_in_named(DEVICE(cpu), nios2_cpu_set_irq, "IRQ", 32);
 #endif
 }