[PATCH v2] hw/rtc/pl031: Send RTC_CHANGE QMP event

[Eric Auger <eric.auger@redhat.com>]

The PL031 currently is not able to report guest RTC change to the QMP
monitor as opposed to mc146818 or spapr RTCs. This patch adds the call
to qapi_event_send_rtc_change() when the Load Register is written. The
value which is reported corresponds to the difference between the guest
reference time and the reference time kept in softmmu/rtc.c.

For instance adding 20s to the guest RTC value will report 20. Adding
an extra 20s to the guest RTC value will report 20 + 20 = 40.

The inclusion of qapi/qapi-types-misc-target.h in hw/rtl/pl031.c
require to compile the PL031 with specific_ss.add() to avoid
./qapi/qapi-types-misc-target.h:18:13: error: attempt to use poisoned
"TARGET_<ARCH>".

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

---

v1 -> v2:
- Use Peter's implementation and remove subsection

Tested with the following script run on guest:

  #!/bin/sh
  old=$(hwclock --show | cut -f1-7 -d' ')
  oldabs=$(date +%s -d "$old")
  newabs=$(expr $oldabs + $1)
  new=$(date -d @"$newabs")
  echo Old: $oldabs $old
  echo New: $newabs $new
  hwclock --set --date "$new"

and compared with x86 behavior.
---
 hw/rtc/meson.build |  2 +-
 hw/rtc/pl031.c     | 10 +++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/hw/rtc/meson.build b/hw/rtc/meson.build
index 7cecdee5ddb..8fd8d8f9a71 100644
--- a/hw/rtc/meson.build
+++ b/hw/rtc/meson.build
@@ -2,7 +2,7 @@
 softmmu_ss.add(when: 'CONFIG_DS1338', if_true: files('ds1338.c'))
 softmmu_ss.add(when: 'CONFIG_M41T80', if_true: files('m41t80.c'))
 softmmu_ss.add(when: 'CONFIG_M48T59', if_true: files('m48t59.c'))
-softmmu_ss.add(when: 'CONFIG_PL031', if_true: files('pl031.c'))
+specific_ss.add(when: 'CONFIG_PL031', if_true: files('pl031.c'))
 softmmu_ss.add(when: 'CONFIG_TWL92230', if_true: files('twl92230.c'))
 softmmu_ss.add(when: ['CONFIG_ISA_BUS', 'CONFIG_M48T59'], if_true: files('m48t59-isa.c'))
 softmmu_ss.add(when: 'CONFIG_XLNX_ZYNQMP', if_true: files('xlnx-zynqmp-rtc.c'))
diff --git a/hw/rtc/pl031.c b/hw/rtc/pl031.c
index 2bbb2062ac8..e7ced90b025 100644
--- a/hw/rtc/pl031.c
+++ b/hw/rtc/pl031.c
@@ -24,6 +24,7 @@
 #include "qemu/log.h"
 #include "qemu/module.h"
 #include "trace.h"
+#include "qapi/qapi-events-misc-target.h"
 
 #define RTC_DR      0x00    /* Data read register */
 #define RTC_MR      0x04    /* Match register */
@@ -136,10 +137,17 @@ static void pl031_write(void * opaque, hwaddr offset,
     trace_pl031_write(offset, value);
 
     switch (offset) {
-    case RTC_LR:
+    case RTC_LR: {
+        struct tm tm;
+
         s->tick_offset += value - pl031_get_count(s);
+
+        qemu_get_timedate(&tm, s->tick_offset);
+        qapi_event_send_rtc_change(qemu_timedate_diff(&tm));
+
         pl031_set_alarm(s);
         break;
+    }
     case RTC_MR:
         s->mr = value;
         pl031_set_alarm(s);
-- 
2.26.3