[PATCH] fsl-imx: Add simple RTC emulation for i.MX6 and i.MX7 boards

[Nikita Ostrenkov <n.ostrenkov@gmail.com>]

Signed-off-by: Nikita Ostrenkov <n.ostrenkov@gmail.com>
---
 hw/misc/imx7_snvs.c         | 59 ++++++++++++++++++++++++++++++++-----
 hw/misc/trace-events        |  4 +--
 include/hw/misc/imx7_snvs.h | 14 ++++++++-
 3 files changed, 67 insertions(+), 10 deletions(-)

diff --git a/hw/misc/imx7_snvs.c b/hw/misc/imx7_snvs.c
index a245f96cd4..7ef3e4901a 100644
--- a/hw/misc/imx7_snvs.c
+++ b/hw/misc/imx7_snvs.c
@@ -13,29 +13,74 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/timer.h"
 #include "hw/misc/imx7_snvs.h"
 #include "qemu/module.h"
+#include "sysemu/sysemu.h"
 #include "sysemu/runstate.h"
 #include "trace.h"
 
+#define RTC_FREQ    32768ULL
+
+static uint64_t imx7_snvs_get_count(IMX7SNVSState *s)
+{
+    int64_t now_ms = qemu_clock_get_ns(rtc_clock) / 1000000;
+    return s->tick_offset + now_ms * RTC_FREQ / 1000;
+}
+
 static uint64_t imx7_snvs_read(void *opaque, hwaddr offset, unsigned size)
 {
-    trace_imx7_snvs_read(offset, 0);
+    IMX7SNVSState *s = opaque;
+    uint64_t ret = 0;
+
+    switch (offset) {
+    case SNVS_LPSRTCMR:
+        ret = (imx7_snvs_get_count(s) >> 32) & 0x7fffU;
+        break;
+    case SNVS_LPSRTCLR:
+        ret = imx7_snvs_get_count(s) & 0xffffffffU;
+        break;
+    case SNVS_LPCR:
+        ret = s->lpcr;
+        break;
+    }
+
+    trace_imx7_snvs_read(offset, ret, size);
 
-    return 0;
+    return ret;
 }
 
 static void imx7_snvs_write(void *opaque, hwaddr offset,
                             uint64_t v, unsigned size)
 {
-    const uint32_t value = v;
-    const uint32_t mask  = SNVS_LPCR_TOP | SNVS_LPCR_DP_EN;
+    trace_imx7_snvs_write(offset, v, size);
 
-    trace_imx7_snvs_write(offset, value);
+    IMX7SNVSState *s = opaque;
 
-    if (offset == SNVS_LPCR && ((value & mask) == mask)) {
-        qemu_system_shutdown_request(SHUTDOWN_CAUSE_GUEST_SHUTDOWN);
+    uint64_t new_value = 0;
+
+    switch (offset) {
+    case SNVS_LPSRTCMR:
+        new_value = (imx7_snvs_get_count(s) & 0xffffffffU) | (v << 32);
+        break;
+    case SNVS_LPSRTCLR:
+        new_value = (imx7_snvs_get_count(s) & 0x7fff00000000ULL) | v;
+        break;
+    case SNVS_LPCR: {
+        s->lpcr = v;
+
+        const uint32_t value = v;
+        const uint32_t mask  = SNVS_LPCR_TOP | SNVS_LPCR_DP_EN;
+
+        if ((value & mask) == mask)
+            qemu_system_shutdown_request(SHUTDOWN_CAUSE_GUEST_SHUTDOWN);
+
+        break;
+    }
     }
+
+    if (offset == SNVS_LPSRTCMR || offset == SNVS_LPSRTCLR)
+        s->tick_offset += new_value - imx7_snvs_get_count(s);
 }
 
 static const struct MemoryRegionOps imx7_snvs_ops = {
diff --git a/hw/misc/trace-events b/hw/misc/trace-events
index 05ff692441..85725506bf 100644
--- a/hw/misc/trace-events
+++ b/hw/misc/trace-events
@@ -116,8 +116,8 @@ imx7_gpr_read(uint64_t offset) "addr 0x%08" PRIx64
 imx7_gpr_write(uint64_t offset, uint64_t value) "addr 0x%08" PRIx64 "value 0x%08" PRIx64
 
 # imx7_snvs.c
-imx7_snvs_read(uint64_t offset, uint32_t value) "addr 0x%08" PRIx64 "value 0x%08" PRIx32
-imx7_snvs_write(uint64_t offset, uint32_t value) "addr 0x%08" PRIx64 "value 0x%08" PRIx32
+imx7_snvs_read(uint64_t offset, uint64_t value, unsigned size) "i.MX SNVS read: offset 0x%08" PRIx64 " value 0x%08" PRIx64 " size %u"
+imx7_snvs_write(uint64_t offset, uint64_t value, unsigned size) "i.MX SNVS write: offset 0x%08" PRIx64 " value 0x%08" PRIx64 " size %u"
 
 # mos6522.c
 mos6522_set_counter(int index, unsigned int val) "T%d.counter=%d"
diff --git a/include/hw/misc/imx7_snvs.h b/include/hw/misc/imx7_snvs.h
index 14a1d6fe6b..406c1fe97f 100644
--- a/include/hw/misc/imx7_snvs.h
+++ b/include/hw/misc/imx7_snvs.h
@@ -20,7 +20,9 @@
 enum IMX7SNVSRegisters {
     SNVS_LPCR = 0x38,
     SNVS_LPCR_TOP   = BIT(6),
-    SNVS_LPCR_DP_EN = BIT(5)
+    SNVS_LPCR_DP_EN = BIT(5),
+    SNVS_LPSRTCMR = 0x050, /* Secure Real Time Counter MSB Register */
+    SNVS_LPSRTCLR = 0x054, /* Secure Real Time Counter LSB Register */
 };
 
 #define TYPE_IMX7_SNVS "imx7.snvs"
@@ -31,6 +33,16 @@ struct IMX7SNVSState {
     SysBusDevice parent_obj;
 
     MemoryRegion mmio;
+
+    /*
+     * Needed to preserve the tick_count across migration, even if the
+     * absolute value of the rtc_clock is different on the source and
+     * destination.
+     */
+    int64_t tick_offset_vmstate;
+    int64_t tick_offset;
+
+    uint64_t lpcr;
 };
 
 #endif /* IMX7_SNVS_H */
-- 
2.34.1