From 97ccc71cfd0b15b8cc7b54405c1231e0e63c7f9c Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 26 May 2024 23:35:16 -0400
Subject: kernel/amd64: Support fetching time since startup

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/arch/amd64/amd64/hpet.c | 25 +++++++++++++++++++++++++
 sys/include/sys/timer.h     |  2 ++
 2 files changed, 27 insertions(+)

diff --git a/sys/arch/amd64/amd64/hpet.c b/sys/arch/amd64/amd64/hpet.c
index 71557eb..f63b47e 100644
--- a/sys/arch/amd64/amd64/hpet.c
+++ b/sys/arch/amd64/amd64/hpet.c
@@ -51,6 +51,9 @@ __KERNEL_META("$Hyra$: hpet.c, Ian Marco Moffett, "
 #define CAP_VENDOR_ID(caps)         __SHIFTOUT(caps, 0xFFFF << 16)
 #define CAP_CLK_PERIOD(caps)        (caps >> 32)
 
+#define FSEC_PER_SECOND 1000000000000000ULL
+#define USEC_PER_SECOND 1000000ULL
+
 static struct timer timer = { 0 };
 static struct hpet *acpi_hpet = NULL;
 static void *hpet_base = NULL;
@@ -129,6 +132,26 @@ hpet_nsleep(size_t ns)
     return hpet_sleep(ns, 1000000);
 }
 
+static size_t
+hpet_time_usec(void)
+{
+    uint64_t period, freq, caps;
+    uint64_t counter;
+
+    caps = hpet_read(HPET_REG_CAPS);
+    period = CAP_CLK_PERIOD(caps);
+    freq = FSEC_PER_SECOND / period;
+
+    counter = hpet_read(HPET_REG_MAIN_COUNTER);
+    return (counter * USEC_PER_SECOND) / freq;
+}
+
+static size_t
+hpet_time_sec(void)
+{
+    return hpet_time_usec() / USEC_PER_SECOND;
+}
+
 int
 hpet_init(void)
 {
@@ -172,6 +195,8 @@ hpet_init(void)
     timer.msleep = hpet_msleep;
     timer.usleep = hpet_usleep;
     timer.nsleep = hpet_nsleep;
+    timer.get_time_usec = hpet_time_usec;
+    timer.get_time_sec = hpet_time_sec;
     register_timer(TIMER_GP, &timer);
 
     /* Not faulty */
diff --git a/sys/include/sys/timer.h b/sys/include/sys/timer.h
index a255bab..e33b2d3 100644
--- a/sys/include/sys/timer.h
+++ b/sys/include/sys/timer.h
@@ -72,6 +72,8 @@ typedef int tmrr_status_t;
 struct timer {
     const char *name;               /* e.g "HPET" */
     size_t(*calibrate)(void);       /* Returns frequency, 0 for unspecified */
+    size_t(*get_time_usec)(void);   /* Time since init (microseconds) */
+    size_t(*get_time_sec)(void);    /* Time since init (seconds) */
     int(*msleep)(size_t ms);
     int(*usleep)(size_t us);
     int(*nsleep)(size_t ns);
-- 
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