From: Yong-Xuan Wang <yongxuan.wang@sifive.com>

The section 4.5.2 of the RISC-V AIA specification says that any write
to a sourcecfg register of an APLIC might (or might not) cause the
corresponding interrupt-pending bit to be set to one if the rectified
input value is high (= 1) under the new source mode.

If an interrupt is asserted before the driver configs its interrupt
type to APLIC, it's pending bit will not be set except a relevant
write to a setip or setipnum register. When we write the interrupt
type to sourcecfg register, if the APLIC device doesn't check
rectified input value and update the pending bit, this interrupt
might never becomes pending.

For APLIC.m, we can manully set pending by setip or setipnum
registers in driver. But for APLIC.w, the pending status totally
depends on the rectified input value, we can't control the pending
status via mmio registers. In this case, hw should check and update
pending status for us when writing sourcecfg registers.

Update QEMU emulation to handle "pre-existing" interrupts.

Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20241004104649.13129-1-yongxuan.wang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
 hw/intc/riscv_aplic.c | 51 ++++++++++++++++++++++++++++---------------
 1 file changed, 33 insertions(+), 18 deletions(-)

diff --git a/hw/intc/riscv_aplic.c b/hw/intc/riscv_aplic.c
index 32edd6d07b..4a262c82f0 100644
--- a/hw/intc/riscv_aplic.c
+++ b/hw/intc/riscv_aplic.c
@@ -159,31 +159,42 @@ static bool is_kvm_aia(bool msimode)
     return kvm_irqchip_in_kernel() && msimode;
 }
 
+static bool riscv_aplic_irq_rectified_val(RISCVAPLICState *aplic,
+                                          uint32_t irq)
+{
+    uint32_t sourcecfg, sm, raw_input, irq_inverted;
+
+    if (!irq || aplic->num_irqs <= irq) {
+        return false;
+    }
+
+    sourcecfg = aplic->sourcecfg[irq];
+    if (sourcecfg & APLIC_SOURCECFG_D) {
+        return false;
+    }
+
+    sm = sourcecfg & APLIC_SOURCECFG_SM_MASK;
+    if (sm == APLIC_SOURCECFG_SM_INACTIVE) {
+        return false;
+    }
+
+    raw_input = (aplic->state[irq] & APLIC_ISTATE_INPUT) ? 1 : 0;
+    irq_inverted = (sm == APLIC_SOURCECFG_SM_LEVEL_LOW ||
+                    sm == APLIC_SOURCECFG_SM_EDGE_FALL) ? 1 : 0;
+
+    return !!(raw_input ^ irq_inverted);
+}
+
 static uint32_t riscv_aplic_read_input_word(RISCVAPLICState *aplic,
                                             uint32_t word)
 {
-    uint32_t i, irq, sourcecfg, sm, raw_input, irq_inverted, ret = 0;
+    uint32_t i, irq, rectified_val, ret = 0;
 
     for (i = 0; i < 32; i++) {
         irq = word * 32 + i;
-        if (!irq || aplic->num_irqs <= irq) {
-            continue;
-        }
 
-        sourcecfg = aplic->sourcecfg[irq];
-        if (sourcecfg & APLIC_SOURCECFG_D) {
-            continue;
-        }
-
-        sm = sourcecfg & APLIC_SOURCECFG_SM_MASK;
-        if (sm == APLIC_SOURCECFG_SM_INACTIVE) {
-            continue;
-        }
-
-        raw_input = (aplic->state[irq] & APLIC_ISTATE_INPUT) ? 1 : 0;
-        irq_inverted = (sm == APLIC_SOURCECFG_SM_LEVEL_LOW ||
-                        sm == APLIC_SOURCECFG_SM_EDGE_FALL) ? 1 : 0;
-        ret |= (raw_input ^ irq_inverted) << i;
+        rectified_val = riscv_aplic_irq_rectified_val(aplic, irq);
+        ret |= rectified_val << i;
     }
 
     return ret;
@@ -702,6 +713,10 @@ static void riscv_aplic_write(void *opaque, hwaddr addr, uint64_t value,
             (aplic->sourcecfg[irq] == 0)) {
             riscv_aplic_set_pending_raw(aplic, irq, false);
             riscv_aplic_set_enabled_raw(aplic, irq, false);
+        } else {
+            if (riscv_aplic_irq_rectified_val(aplic, irq)) {
+                riscv_aplic_set_pending_raw(aplic, irq, true);
+            }
         }
     } else if (aplic->mmode && aplic->msimode &&
                (addr == APLIC_MMSICFGADDR)) {
-- 
2.47.0