target/nios2: Implement EIC interrupt processing

This is the cpu side of the operation.  Register one irq line,
called EIC.  Split out the rather different processing to a
separate function.

Delay initialization of gpio irqs until realize.  We need to
provide a window after init in which the board can set eic_present.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220421151735.31996-57-richard.henderson@linaro.org>

3 files changed, 129 insertions, 22 deletions

diff --git a/target/nios2/cpu.c b/target/nios2/cpu.c
index d043c02fcd..19b2409974 100644
--- a/target/nios2/cpu.c
+++ b/target/nios2/cpu.c
@@ -63,7 +63,19 @@ static void nios2_cpu_reset(DeviceState *dev)
 }
 
 #ifndef CONFIG_USER_ONLY
-static void nios2_cpu_set_irq(void *opaque, int irq, int level)
+static void eic_set_irq(void *opaque, int irq, int level)
+{
+    Nios2CPU *cpu = opaque;
+    CPUState *cs = CPU(cpu);
+
+    if (level) {
+        cpu_interrupt(cs, CPU_INTERRUPT_HARD);
+    } else {
+        cpu_reset_interrupt(cs, CPU_INTERRUPT_HARD);
+    }
+}
+
+static void iic_set_irq(void *opaque, int irq, int level)
 {
     Nios2CPU *cpu = opaque;
     CPUNios2State *env = &cpu->env;
@@ -87,15 +99,6 @@ 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
 }
 
@@ -128,10 +131,18 @@ static void realize_cr_status(CPUState *cs)
     RO_REG(CR_EXCEPTION);
     WR_REG(CR_BADADDR);
 
-    /* TODO: These control registers are not present with the EIC. */
-    RO_FIELD(CR_STATUS, RSIE);
-    WR_REG(CR_IENABLE);
-    RO_REG(CR_IPENDING);
+    if (cpu->eic_present) {
+        WR_FIELD(CR_STATUS, RSIE);
+        RO_FIELD(CR_STATUS, NMI);
+        WR_FIELD(CR_STATUS, PRS);
+        RO_FIELD(CR_STATUS, CRS);
+        WR_FIELD(CR_STATUS, IL);
+        WR_FIELD(CR_STATUS, IH);
+    } else {
+        RO_FIELD(CR_STATUS, RSIE);
+        WR_REG(CR_IENABLE);
+        RO_REG(CR_IPENDING);
+    }
 
     if (cpu->mmu_present) {
         WR_FIELD(CR_STATUS, U);
@@ -170,6 +181,14 @@ static void nios2_cpu_realizefn(DeviceState *dev, Error **errp)
     Nios2CPUClass *ncc = NIOS2_CPU_GET_CLASS(dev);
     Error *local_err = NULL;
 
+#ifndef CONFIG_USER_ONLY
+    if (cpu->eic_present) {
+        qdev_init_gpio_in_named(DEVICE(cpu), eic_set_irq, "EIC", 1);
+    } else {
+        qdev_init_gpio_in_named(DEVICE(cpu), iic_set_irq, "IRQ", 32);
+    }
+#endif
+
     cpu_exec_realizefn(cs, &local_err);
     if (local_err != NULL) {
         error_propagate(errp, local_err);
@@ -187,18 +206,49 @@ static void nios2_cpu_realizefn(DeviceState *dev, Error **errp)
 }
 
 #ifndef CONFIG_USER_ONLY
-static bool nios2_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
+static bool eic_take_interrupt(Nios2CPU *cpu)
 {
-    Nios2CPU *cpu = NIOS2_CPU(cs);
     CPUNios2State *env = &cpu->env;
+    const uint32_t status = env->ctrl[CR_STATUS];
 
-    if ((interrupt_request & CPU_INTERRUPT_HARD) &&
-        (env->ctrl[CR_STATUS] & CR_STATUS_PIE) &&
-        (env->ctrl[CR_IPENDING] & env->ctrl[CR_IENABLE])) {
-        cs->exception_index = EXCP_IRQ;
-        nios2_cpu_do_interrupt(cs);
+    if (cpu->rnmi) {
+        return !(status & CR_STATUS_NMI);
+    }
+    if (!(status & CR_STATUS_PIE)) {
+        return false;
+    }
+    if (cpu->ril <= FIELD_EX32(status, CR_STATUS, IL)) {
+        return false;
+    }
+    if (cpu->rrs != FIELD_EX32(status, CR_STATUS, CRS)) {
         return true;
     }
+    return status & CR_STATUS_RSIE;
+}
+
+static bool iic_take_interrupt(Nios2CPU *cpu)
+{
+    CPUNios2State *env = &cpu->env;
+
+    if (!(env->ctrl[CR_STATUS] & CR_STATUS_PIE)) {
+        return false;
+    }
+    return env->ctrl[CR_IPENDING] & env->ctrl[CR_IENABLE];
+}
+
+static bool nios2_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
+{
+    Nios2CPU *cpu = NIOS2_CPU(cs);
+
+    if (interrupt_request & CPU_INTERRUPT_HARD) {
+        if (cpu->eic_present
+            ? eic_take_interrupt(cpu)
+            : iic_take_interrupt(cpu)) {
+            cs->exception_index = EXCP_IRQ;
+            nios2_cpu_do_interrupt(cs);
+            return true;
+        }
+    }
     return false;
 }
 #endif /* !CONFIG_USER_ONLY */
diff --git a/target/nios2/cpu.h b/target/nios2/cpu.h
index eb171a33e6..5474b1c404 100644
--- a/target/nios2/cpu.h
+++ b/target/nios2/cpu.h
@@ -114,6 +114,7 @@ FIELD(CR_STATUS, CRS, 10, 6)
 FIELD(CR_STATUS, PRS, 16, 6)
 FIELD(CR_STATUS, NMI, 22, 1)
 FIELD(CR_STATUS, RSIE, 23, 1)
+FIELD(CR_STATUS, SRS, 31, 1)  /* only in sstatus */
 
 #define CR_STATUS_PIE    R_CR_STATUS_PIE_MASK
 #define CR_STATUS_U      R_CR_STATUS_U_MASK
@@ -121,6 +122,7 @@ FIELD(CR_STATUS, RSIE, 23, 1)
 #define CR_STATUS_IH     R_CR_STATUS_IH_MASK
 #define CR_STATUS_NMI    R_CR_STATUS_NMI_MASK
 #define CR_STATUS_RSIE   R_CR_STATUS_RSIE_MASK
+#define CR_STATUS_SRS    R_CR_STATUS_SRS_MASK
 
 FIELD(CR_EXCEPTION, CAUSE, 2, 5)
 FIELD(CR_EXCEPTION, ECCFTL, 31, 1)
@@ -234,6 +236,12 @@ struct ArchCPU {
 
     /* Bits within each control register which are reserved or readonly. */
     ControlRegState cr_state[NUM_CR_REGS];
+
+    /* External Interrupt Controller Interface */
+    uint32_t rha; /* Requested handler address */
+    uint32_t ril; /* Requested interrupt level */
+    uint32_t rrs; /* Requested register set */
+    bool rnmi;    /* Requested nonmaskable interrupt */
 };
 
 
diff --git a/target/nios2/helper.c b/target/nios2/helper.c
index 2e9fea4a01..e256d1528e 100644
--- a/target/nios2/helper.c
+++ b/target/nios2/helper.c
@@ -37,6 +37,10 @@ static void do_exception(Nios2CPU *cpu, uint32_t exception_addr,
     uint32_t old_status = env->ctrl[CR_STATUS];
     uint32_t new_status = old_status;
 
+    /* With shadow regs, exceptions are always taken into CRS 0. */
+    new_status &= ~R_CR_STATUS_CRS_MASK;
+    env->regs = env->shadow_regs[0];
+
     if ((old_status & CR_STATUS_EH) == 0) {
         int r_ea = R_EA, cr_es = CR_ESTATUS;
 
@@ -60,6 +64,14 @@ static void do_exception(Nios2CPU *cpu, uint32_t exception_addr,
                                        CR_TLBMISC_DBL);
             env->ctrl[CR_TLBMISC] |= tlbmisc_set;
         }
+
+        /*
+         * With shadow regs, and EH == 0, PRS is set from CRS.
+         * At least, so says Table 3-9, and some other text,
+         * though Table 3-38 says otherwise.
+         */
+        new_status = FIELD_DP32(new_status, CR_STATUS, PRS,
+                                FIELD_EX32(old_status, CR_STATUS, CRS));
     }
 
     new_status &= ~(CR_STATUS_PIE | CR_STATUS_U);
@@ -77,6 +89,39 @@ static void do_iic_irq(Nios2CPU *cpu)
     do_exception(cpu, cpu->exception_addr, 0, false);
 }
 
+static void do_eic_irq(Nios2CPU *cpu)
+{
+    CPUNios2State *env = &cpu->env;
+    uint32_t old_status = env->ctrl[CR_STATUS];
+    uint32_t new_status = old_status;
+    uint32_t old_rs = FIELD_EX32(old_status, CR_STATUS, CRS);
+    uint32_t new_rs = cpu->rrs;
+
+    new_status = FIELD_DP32(new_status, CR_STATUS, CRS, new_rs);
+    new_status = FIELD_DP32(new_status, CR_STATUS, IL, cpu->ril);
+    new_status = FIELD_DP32(new_status, CR_STATUS, NMI, cpu->rnmi);
+    new_status &= ~(CR_STATUS_RSIE | CR_STATUS_U);
+    new_status |= CR_STATUS_IH;
+
+    if (!(new_status & CR_STATUS_EH)) {
+        new_status = FIELD_DP32(new_status, CR_STATUS, PRS, old_rs);
+        if (new_rs == 0) {
+            env->ctrl[CR_ESTATUS] = old_status;
+        } else {
+            if (new_rs != old_rs) {
+                old_status |= CR_STATUS_SRS;
+            }
+            env->shadow_regs[new_rs][R_SSTATUS] = old_status;
+        }
+        env->shadow_regs[new_rs][R_EA] = env->pc + 4;
+    }
+
+    env->ctrl[CR_STATUS] = new_status;
+    nios2_update_crs(env);
+
+    env->pc = cpu->rha;
+}
+
 void nios2_cpu_do_interrupt(CPUState *cs)
 {
     Nios2CPU *cpu = NIOS2_CPU(cs);
@@ -142,7 +187,11 @@ void nios2_cpu_do_interrupt(CPUState *cs)
 
     switch (cs->exception_index) {
     case EXCP_IRQ:
-        do_iic_irq(cpu);
+        if (cpu->eic_present) {
+            do_eic_irq(cpu);
+        } else {
+            do_iic_irq(cpu);
+        }
         break;
 
     case EXCP_TLB_D: