hw/mips: implement GIC Interval Timer

The interval timer is similar to the CP0 Count/Compare timer within
each processor. The difference is the GIC_SH_COUNTER register is global
to the system so that all processors have the same time reference.

To ease implementation, all VPs are having its own QEMU timer but sharing
global settings and registers such as GIC_SH_CONFIG.COUTNSTOP and
GIC_SH_COUNTER.

MIPS GIC Interval Timer does support upto 64 bits of Count register but
in this implementation it is limited to 32 bits only.

Signed-off-by: Yongbok Kim <yongbok.kim@imgtec.com>
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>

1 files changed, 142 insertions, 0 deletions

diff --git a/hw/timer/mips_gictimer.c b/hw/timer/mips_gictimer.c
new file mode 100644
index 0000000000..3698889475
--- /dev/null
+++ b/hw/timer/mips_gictimer.c
@@ -0,0 +1,142 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2016 Imagination Technologies
+ */
+
+#include "qemu/osdep.h"
+#include "hw/hw.h"
+#include "hw/sysbus.h"
+#include "qemu/timer.h"
+#include "hw/timer/mips_gictimer.h"
+
+#define TIMER_PERIOD 10 /* 10 ns period for 100 Mhz frequency */
+
+static void gic_vptimer_update(MIPSGICTimerState *gictimer,
+                                   uint32_t vp_index, uint64_t now)
+{
+    uint64_t next;
+    uint32_t wait;
+
+    wait = gictimer->vptimers[vp_index].comparelo - gictimer->sh_counterlo -
+           (uint32_t)(now / TIMER_PERIOD);
+    next = now + (uint64_t)wait * TIMER_PERIOD;
+
+    timer_mod(gictimer->vptimers[vp_index].qtimer, next);
+}
+
+static void gic_vptimer_expire(MIPSGICTimerState *gictimer, uint32_t vp_index,
+                               uint64_t now)
+{
+    if (gictimer->countstop) {
+        /* timer stopped */
+        return;
+    }
+    gictimer->cb(gictimer->opaque, vp_index);
+    gic_vptimer_update(gictimer, vp_index, now);
+}
+
+static void gic_vptimer_cb(void *opaque)
+{
+    MIPSGICTimerVPState *vptimer = opaque;
+    MIPSGICTimerState *gictimer = vptimer->gictimer;
+    gic_vptimer_expire(gictimer, vptimer->vp_index,
+                       qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
+}
+
+uint32_t mips_gictimer_get_sh_count(MIPSGICTimerState *gictimer)
+{
+    int i;
+    if (gictimer->countstop) {
+        return gictimer->sh_counterlo;
+    } else {
+        uint64_t now;
+        now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+        for (i = 0; i < gictimer->num_vps; i++) {
+            if (timer_pending(gictimer->vptimers[i].qtimer)
+                && timer_expired(gictimer->vptimers[i].qtimer, now)) {
+                /* The timer has already expired.  */
+                gic_vptimer_expire(gictimer, i, now);
+            }
+        }
+        return gictimer->sh_counterlo + (uint32_t)(now / TIMER_PERIOD);
+    }
+}
+
+void mips_gictimer_store_sh_count(MIPSGICTimerState *gictimer, uint64_t count)
+{
+    int i;
+    uint64_t now;
+
+    if (gictimer->countstop || !gictimer->vptimers[0].qtimer) {
+        gictimer->sh_counterlo = count;
+    } else {
+        /* Store new count register */
+        now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+        gictimer->sh_counterlo = count - (uint32_t)(now / TIMER_PERIOD);
+        /* Update timer timer */
+        for (i = 0; i < gictimer->num_vps; i++) {
+            gic_vptimer_update(gictimer, i, now);
+        }
+    }
+}
+
+uint32_t mips_gictimer_get_vp_compare(MIPSGICTimerState *gictimer,
+                                      uint32_t vp_index)
+{
+    return gictimer->vptimers[vp_index].comparelo;
+}
+
+void mips_gictimer_store_vp_compare(MIPSGICTimerState *gictimer,
+                                    uint32_t vp_index, uint64_t compare)
+{
+    gictimer->vptimers[vp_index].comparelo = (uint32_t) compare;
+    gic_vptimer_update(gictimer, vp_index,
+                       qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
+}
+
+uint8_t mips_gictimer_get_countstop(MIPSGICTimerState *gictimer)
+{
+    return gictimer->countstop;
+}
+
+void mips_gictimer_start_count(MIPSGICTimerState *gictimer)
+{
+    gictimer->countstop = 0;
+    mips_gictimer_store_sh_count(gictimer, gictimer->sh_counterlo);
+}
+
+void mips_gictimer_stop_count(MIPSGICTimerState *gictimer)
+{
+    int i;
+
+    gictimer->countstop = 1;
+    /* Store the current value */
+    gictimer->sh_counterlo +=
+        (uint32_t)(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / TIMER_PERIOD);
+    for (i = 0; i < gictimer->num_vps; i++) {
+        timer_del(gictimer->vptimers[i].qtimer);
+    }
+}
+
+MIPSGICTimerState *mips_gictimer_init(void *opaque, uint32_t nvps,
+                                      MIPSGICTimerCB *cb)
+{
+    int i;
+    MIPSGICTimerState *gictimer = g_new(MIPSGICTimerState, 1);
+    gictimer->vptimers = g_new(MIPSGICTimerVPState, nvps);
+    gictimer->countstop = 1;
+    gictimer->num_vps = nvps;
+    gictimer->opaque = opaque;
+    gictimer->cb = cb;
+    for (i = 0; i < nvps; i++) {
+        gictimer->vptimers[i].gictimer = gictimer;
+        gictimer->vptimers[i].vp_index = i;
+        gictimer->vptimers[i].qtimer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
+                                            &gic_vptimer_cb,
+                                            &gictimer->vptimers[i]);
+    }
+    return gictimer;
+}