S5L8700: implement timer driver

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21801 a1c6a512-1295-4272-9138-f99709370657

2 files changed, 106 insertions, 0 deletions

diff --git a/firmware/export/s5l8700.h b/firmware/export/s5l8700.h
index c026328f7f..7583d291f6 100644
--- a/firmware/export/s5l8700.h
+++ b/firmware/export/s5l8700.h
@@ -23,6 +23,8 @@
 #define REG16_PTR_T volatile uint16_t *
 #define REG32_PTR_T volatile uint32_t *
 
+#define TIMER_FREQ  50000000L
+
 /* 04. CALMADM2E */
 
 /* Following registers are mapped on IO Area in data memory area of Calm. */
diff --git a/firmware/target/arm/s5l8700/timer-s5l8700.c b/firmware/target/arm/s5l8700/timer-s5l8700.c
new file mode 100644
index 0000000000..f9bef1c956
--- /dev/null
+++ b/firmware/target/arm/s5l8700/timer-s5l8700.c
@@ -0,0 +1,104 @@
+/***************************************************************************
+*             __________               __   ___.
+*   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+*   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+*   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+*   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+*                     \/            \/     \/    \/            \/
+* $Id$
+*
+* Copyright (C) 2008 Rafaël Carré
+*
+* This program is free software; you can redistribute it and/or
+* modify it under the terms of the GNU General Public License
+* as published by the Free Software Foundation; either version 2
+* of the License, or (at your option) any later version.
+*
+* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+* KIND, either express or implied.
+*
+****************************************************************************/
+
+#include "config.h"
+
+#include "inttypes.h"
+#include "s5l8700.h"
+#include "system.h"
+#include "timer.h"
+
+/*  Timer driver for the S5L8700
+
+    The S5L8700 timer resolution is only 16-bit. Larger counts are done by using
+    both the clock-select and the clock prescaler to bring the count down into
+    the range of the 16-bit counter.
+    
+    TODO: investigate why the timer seems to count twice as fast as expected
+*/
+
+void INT_TIMERD(void)
+{
+    /* clear interrupt */
+    TDCON = TDCON;
+    
+    if (pfn_timer != NULL) {
+        pfn_timer();
+    }
+}
+
+bool timer_set(long cycles, bool start)
+{
+    static const int cs_table[] = {1, 2, 4, 6};
+    int prescale, cs;
+    long count;
+
+    /* stop and clear timer */
+    TDCMD = (1 << 1);   /* TD_CLR */
+
+    /* optionally unregister any previously registered timer user */
+    if (start) {
+        if (pfn_unregister != NULL) {
+            pfn_unregister();
+            pfn_unregister = NULL;
+        }
+    }
+
+    /* scale the count down with the clock select */
+    for (cs = 0; cs < 4; cs++) {
+        count = cycles >> cs_table[cs];
+        if ((count < 65536) || (cs == 3)) {
+            break;
+        }
+    }
+    
+    /* scale the count down with the prescaler */
+    prescale = 1;
+    while (count >= 65536) {
+        count >>= 1;
+        prescale <<= 1;
+    }
+
+    /* configure timer */
+    TDCON = (1 << 12) |     /* TD_INT0_EN */
+            (cs << 8) |     /* TS_CS */
+            (0 << 4);       /* TD_MODE_SEL, 0 = interval mode */
+    TDPRE = prescale - 1;
+    TDDATA0 = count;
+    TDCMD = (1 << 0);       /* TD_ENABLE */
+
+    /* enable interrupt */
+    INTMSK |= (1 << 9);
+    
+    return true;
+}
+
+bool timer_start(void)
+{
+    TDCMD = (1 << 0);       /* TD_ENABLE */
+    return true;
+}
+
+void timer_stop(void)
+{
+    TDCMD = (0 << 0);       /* TD_ENABLE */
+}
+