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authorGururaja Hebbar K R <gururajakr@sanyo.co.in>2008-08-25 11:11:34 +0200
committerJean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>2008-08-25 13:00:03 +0200
commite8f1207bbf2df6fb693ee1aa3329b2014c92e5e6 (patch)
tree5cc265595c6f75283f7e67e8d3a3ea5575afa868 /cpu/arm926ejs/versatile/timer.c
parent535cfa4f3de86cf48d6c0af1daf33aebdca089f9 (diff)
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Correct ARM Versatile Timer Initialization
- According to ARM Dual-Timer Module (SP804) TRM (ARM DDI0271), -- Timer Value Register @ TIMER Base + 4 is Read-only. -- Prescale Value (Bits 3-2 of TIMER Control register) can only be one of 00,01,10. 11 is undefined. -- CFG_HZ for Versatile board is set to #define CFG_HZ (1000000 / 256) So Prescale bits is set to indicate - 8 Stages of Prescale, Clock divided by 256 - The Timer Control Register has one Undefined/Shouldn't Use Bit So we should do read/modify/write Operation Signed-off-by: Gururaja Hebbar <gururajakr@sanyo.co.in>
Diffstat (limited to 'cpu/arm926ejs/versatile/timer.c')
-rwxr-xr-x[-rw-r--r--]cpu/arm926ejs/versatile/timer.c39
1 files changed, 35 insertions, 4 deletions
diff --git a/cpu/arm926ejs/versatile/timer.c b/cpu/arm926ejs/versatile/timer.c
index 32872d2..f01f318 100644..100755
--- a/cpu/arm926ejs/versatile/timer.c
+++ b/cpu/arm926ejs/versatile/timer.c
@@ -46,12 +46,43 @@
static ulong timestamp;
static ulong lastdec;
-/* nothing really to do with interrupts, just starts up a counter. */
+#define TIMER_ENABLE (1 << 7)
+#define TIMER_MODE_MSK (1 << 6)
+#define TIMER_MODE_FR (0 << 6)
+#define TIMER_MODE_PD (1 << 6)
+
+#define TIMER_INT_EN (1 << 5)
+#define TIMER_PRS_MSK (3 << 2)
+#define TIMER_PRS_8S (1 << 3)
+#define TIMER_SIZE_MSK (1 << 2)
+#define TIMER_ONE_SHT (1 << 0)
+
int timer_init (void)
{
- *(volatile ulong *)(CFG_TIMERBASE + 0) = CFG_TIMER_RELOAD; /* TimerLoad */
- *(volatile ulong *)(CFG_TIMERBASE + 4) = CFG_TIMER_RELOAD; /* TimerValue */
- *(volatile ulong *)(CFG_TIMERBASE + 8) = 0x8C;
+ ulong tmr_ctrl_val;
+
+ /* 1st disable the Timer */
+ tmr_ctrl_val = *(volatile ulong *)(CFG_TIMERBASE + 8);
+ tmr_ctrl_val &= ~TIMER_ENABLE;
+ *(volatile ulong *)(CFG_TIMERBASE + 8) = tmr_ctrl_val;
+
+ /*
+ * The Timer Control Register has one Undefined/Shouldn't Use Bit
+ * So we should do read/modify/write Operation
+ */
+
+ /*
+ * Timer Mode : Free Running
+ * Interrupt : Disabled
+ * Prescale : 8 Stage, Clk/256
+ * Tmr Siz : 16 Bit Counter
+ * Tmr in Wrapping Mode
+ */
+ tmr_ctrl_val = *(volatile ulong *)(CFG_TIMERBASE + 8);
+ tmr_ctrl_val &= ~(TIMER_MODE_MSK | TIMER_INT_EN | TIMER_PRS_MSK | TIMER_SIZE_MSK | TIMER_ONE_SHT );
+ tmr_ctrl_val |= (TIMER_ENABLE | TIMER_PRS_8S);
+
+ *(volatile ulong *)(CFG_TIMERBASE + 8) = tmr_ctrl_val;
/* init the timestamp and lastdec value */
reset_timer_masked();