[PATCH 07/12] i386/pit: Tune delays

[Damien Zammit]

- Add half a clock tick for more accuracy
- Start the pit countdown during pit_sleep
- Add pit_mdelay and pit_udelay functions
---
 i386/i386/pit.c | 24 ++++++++++++++++++++----
 i386/i386/pit.h |  2 ++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/i386/i386/pit.c b/i386/i386/pit.c
index 0ead8c9b..7373a38e 100644
--- a/i386/i386/pit.c
+++ b/i386/i386/pit.c
@@ -83,6 +83,12 @@ pit_prepare_sleep(int hz)
     outb (PITCTR2_PORT, lsb);
     val = inb(POST_PORT); /* ~1us i/o delay */
     outb (PITCTR2_PORT, msb);
+}
+
+void
+pit_sleep(void)
+{
+    int val;

     /* Start counting down */
     val = inb(PITAUX_PORT);
@@ -90,13 +96,23 @@ pit_prepare_sleep(int hz)
     outb (PITAUX_PORT, val); /* Gate low */
     val |= PITAUX_GATE2;
     outb (PITAUX_PORT, val); /* Gate high */
+
+    /* Wait until counter reaches zero */
+    while ((inb(PITAUX_PORT) & PITAUX_VAL) == 0);
 }

 void
-pit_sleep(void)
+pit_udelay(int usec)
 {
-    /* Wait until counter reaches zero */
-    while ((inb(PITAUX_PORT) & PITAUX_VAL) == 0);
+    pit_prepare_sleep(1000000 / usec);
+    pit_sleep();
+}
+
+void
+pit_mdelay(int msec)
+{
+    pit_prepare_sleep(1000 / msec);
+    pit_sleep();
 }

 void
@@ -115,7 +131,7 @@ clkstart(void)
         * timers you do not use
         */
        outb(pitctl_port, pit0_mode);
-       clknumb = CLKNUM/hz;
+       clknumb = (CLKNUM + hz / 2) / hz;
        byte = clknumb;
        outb(pitctr0_port, byte);
        byte = clknumb>>8;
diff --git a/i386/i386/pit.h b/i386/i386/pit.h
index bac4e985..51c4111d 100644
--- a/i386/i386/pit.h
+++ b/i386/i386/pit.h
@@ -91,5 +91,7 @@ WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 extern void clkstart(void);
 extern void pit_prepare_sleep(int hz);
 extern void pit_sleep(void);
+extern void pit_udelay(int usec);
+extern void pit_mdelay(int msec);

 #endif /* _I386_PIT_H_ */
--
2.34.1