hpet/rtc: Rework RTC IRQ replacement by HPET

Allow the intercept the RTC IRQ for the HPET legacy mode. Then push
routing to IRQ8 completely into the HPET. This allows to turn
hpet_in_legacy_mode() into a private function. Furthermore, this stops
the RTC from clearing IRQ8 even if the HPET is in control.

This patch comes with a side effect: The RTC timers will no longer be
stoppend when there is no IRQ consumer, possibly causing a minor
performance degration. But as the guest may want to redirect the RTC to
the SCI in that mode, it should normally disable unused IRQ source
anyway.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

1 files changed, 21 insertions, 7 deletions

diff --git a/hw/hpet.c b/hw/hpet.c
index 041dd84cfd..edfe02eabf 100644
--- a/hw/hpet.c
+++ b/hw/hpet.c
@@ -30,6 +30,7 @@
 #include "qemu-timer.h"
 #include "hpet_emul.h"
 #include "sysbus.h"
+#include "mc146818rtc.h"
 
 //#define HPET_DEBUG
 #ifdef HPET_DEBUG
@@ -58,6 +59,7 @@ typedef struct HPETState {
     SysBusDevice busdev;
     uint64_t hpet_offset;
     qemu_irq irqs[HPET_NUM_IRQ_ROUTES];
+    uint8_t rtc_irq_level;
     HPETTimer timer[HPET_NUM_TIMERS];
 
     /* Memory-mapped, software visible registers */
@@ -69,12 +71,9 @@ typedef struct HPETState {
 
 static HPETState *hpet_statep;
 
-uint32_t hpet_in_legacy_mode(void)
+static uint32_t hpet_in_legacy_mode(HPETState *s)
 {
-    if (!hpet_statep) {
-        return 0;
-    }
-    return hpet_statep->config & HPET_CFG_LEGACY;
+    return s->config & HPET_CFG_LEGACY;
 }
 
 static uint32_t timer_int_route(struct HPETTimer *timer)
@@ -166,12 +165,12 @@ static void update_irq(struct HPETTimer *timer)
 {
     int route;
 
-    if (timer->tn <= 1 && hpet_in_legacy_mode()) {
+    if (timer->tn <= 1 && hpet_in_legacy_mode(timer->state)) {
         /* if LegacyReplacementRoute bit is set, HPET specification requires
          * timer0 be routed to IRQ0 in NON-APIC or IRQ2 in the I/O APIC,
          * timer1 be routed to IRQ8 in NON-APIC or IRQ8 in the I/O APIC.
          */
-        route = (timer->tn == 0) ? 0 : 8;
+        route = (timer->tn == 0) ? 0 : RTC_ISA_IRQ;
     } else {
         route = timer_int_route(timer);
     }
@@ -515,8 +514,10 @@ static void hpet_ram_writel(void *opaque, target_phys_addr_t addr,
             /* i8254 and RTC are disabled when HPET is in legacy mode */
             if (activating_bit(old_val, new_val, HPET_CFG_LEGACY)) {
                 hpet_pit_disable();
+                qemu_irq_lower(s->irqs[RTC_ISA_IRQ]);
             } else if (deactivating_bit(old_val, new_val, HPET_CFG_LEGACY)) {
                 hpet_pit_enable();
+                qemu_set_irq(s->irqs[RTC_ISA_IRQ], s->rtc_irq_level);
             }
             break;
         case HPET_CFG + 4:
@@ -607,6 +608,16 @@ static void hpet_reset(DeviceState *d)
     count = 1;
 }
 
+static void hpet_handle_rtc_irq(void *opaque, int n, int level)
+{
+    HPETState *s = FROM_SYSBUS(HPETState, opaque);
+
+    s->rtc_irq_level = level;
+    if (!hpet_in_legacy_mode(s)) {
+        qemu_set_irq(s->irqs[RTC_ISA_IRQ], level);
+    }
+}
+
 static int hpet_init(SysBusDevice *dev)
 {
     HPETState *s = FROM_SYSBUS(HPETState, dev);
@@ -625,6 +636,9 @@ static int hpet_init(SysBusDevice *dev)
         timer->state = s;
     }
 
+    isa_reserve_irq(RTC_ISA_IRQ);
+    qdev_init_gpio_in(&dev->qdev, hpet_handle_rtc_irq, 1);
+
     /* HPET Area */
     iomemtype = cpu_register_io_memory(hpet_ram_read,
                                        hpet_ram_write, s);