[Skiboot] [RFC] hw/fake-rtc: Add support for emulated rtc clock
Vaibhav Jain
vaibhav at linux.vnet.ibm.com
Mon Sep 7 19:04:20 AEST 2015
This patch adds support for an emulated rtc clock over existing fake rtc
implementation for generic platform (e.g BML). Presently a fake rtc
clock is initialized when reserved region named 'ibm,fake-rtc' is
present in the boot device tree. This mem-region points to the initial
value of bcd coded date-time values. However as this region is in system
memory hence its not updated with time. This results in an error from
hwclock tool which tries to detect a change in system clock and then
complains "Timed out waiting for time change."
The patch overcomes this issue by emulating an rtc clock that's driven
by a periodically scheduled timer. The initial epoch is set from the
values at "ibm,fake-rtc" memory region. It then creates the periodic
timer and on each tick the rtc counter is incremented.
Signed-off-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
---
hw/fake-rtc.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 75 insertions(+), 9 deletions(-)
diff --git a/hw/fake-rtc.c b/hw/fake-rtc.c
index 1b7c473..7b447fc 100644
--- a/hw/fake-rtc.c
+++ b/hw/fake-rtc.c
@@ -17,14 +17,30 @@
#include <skiboot.h>
#include <opal.h>
#include <mem_region.h>
+#include <device.h>
+#include <timebase.h>
+#include <timer.h>
+#include <time-utils.h>
+#include <lock.h>
-static uint32_t *fake_ymd;
-static uint64_t *fake_hmsm;
+/* use it to store and hold rtc value */
+static struct timer emulation_timer;
+
+/* timebase when last synchronization happened */
+static unsigned long tb_synctime;
+
+/* current rtc value */
+struct tm tm_offset;
+
+/* protects tm_offset & tb_synctime */
+struct lock emulation_lock;
static int64_t fake_rtc_write(uint32_t ymd, uint64_t hmsm)
{
- *fake_ymd = ymd;
- *fake_hmsm = hmsm;
+ lock(&emulation_lock);
+ datetime_to_tm(ymd, hmsm, &tm_offset);
+ tb_synctime = mftb();
+ unlock(&emulation_lock);
return OPAL_SUCCESS;
}
@@ -34,16 +50,51 @@ static int64_t fake_rtc_read(uint32_t *ymd, uint64_t *hmsm)
if (!ymd || !hmsm)
return OPAL_PARAMETER;
- *ymd = *fake_ymd;
- *hmsm = *fake_hmsm;
+ /* Read emulated clock */
+ lock(&emulation_lock);
+ tm_to_datetime(&tm_offset, ymd, hmsm);
+ unlock(&emulation_lock);
return OPAL_SUCCESS;
}
+/* update the emulated rtc. In case more than 60 seconds have passed
+ * since last sync then recompute the tm_offset.
+ */
+static void __emulated_rtc_update(struct timer *tm __unused,
+ void *data __unused)
+{
+ time_t sec;
+
+ if (try_lock(&emulation_lock)) {
+
+ sec = tb_to_secs(mftb() - tb_synctime);
+ tb_synctime = mftb();
+
+ if ((sec + tm_offset.tm_sec) >= 60) {
+ sec += mktime(&tm_offset);
+ gmtime_r(&sec, &tm_offset);
+ } else {
+ tm_offset.tm_sec += sec;
+ }
+
+ unlock(&emulation_lock);
+ }
+ /* reschedule the timer */
+ schedule_timer(&emulation_timer, secs_to_tb(1));
+}
+
void fake_rtc_init(void)
{
struct mem_region *rtc_region = NULL;
- uint32_t *rtc = NULL;
+ uint32_t *rtc = NULL, *fake_ymd;
+ uint64_t *fake_hmsm;
+ struct dt_node *np;
+ const time_t inittime = 0;
+
+ /* Init the timer to 0 epoch */
+ gmtime_r(&inittime, &tm_offset);
+ tb_synctime = mftb();
/* Read initial values from reserved memory */
rtc_region = find_mem_region("ibm,fake-rtc");
@@ -54,14 +105,29 @@ void fake_rtc_init(void)
return;
}
+ /* Fetch the initial rtc values */
rtc = (uint32_t *) rtc_region->start;
fake_ymd = rtc;
fake_hmsm = ((uint64_t *) &rtc[1]);
- prlog(PR_TRACE, "Init fake RTC to 0x%x 0x%llx\n",
- *fake_ymd, *fake_hmsm);
+ datetime_to_tm(*fake_ymd, *fake_hmsm, &tm_offset);
+ init_lock(&emulation_lock);
+
+ /* Schedule Tick Timer */
+ init_timer(&emulation_timer, __emulated_rtc_update, NULL);
+ schedule_timer(&emulation_timer, secs_to_tb(1));
+
+ /* Register opal calls */
opal_register(OPAL_RTC_READ, fake_rtc_read, 2);
opal_register(OPAL_RTC_WRITE, fake_rtc_write, 2);
+
+ /* add the fake rtc dt node */
+ np = dt_new(opal_node, "rtc");
+ dt_add_property_strings(np, "compatible", "ibm,opal-rtc");
+
+ prlog(PR_TRACE, "Init fake RTC to Date:%d-%d-%d Time:%d-%d-%d\n",
+ tm_offset.tm_mon, tm_offset.tm_mday, tm_offset.tm_year,
+ tm_offset.tm_hour, tm_offset.tm_min, tm_offset.tm_sec);
}
--
2.2.1
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