[ARM] Remove 200Hz -> 100Hz conversion for ebsa110 timer.

We now really run the ebsa110 kernel timer at 200Hz, and convert
where necessary to 100Hz for user space.

2 files changed, 79 insertions, 8 deletions

diff --git a/include/asm-arm/arch-ebsa110/param.h b/include/asm-arm/arch-ebsa110/param.h
index f077b717193d..13a9fc1b7a25 100644
--- a/include/asm-arm/arch-ebsa110/param.h
+++ b/include/asm-arm/arch-ebsa110/param.h
@@ -1,3 +1,4 @@
 /*
  *  linux/include/asm-arm/arch-ebsa110/param.h
  */
+#define __KERNEL_HZ	200
diff --git a/include/asm-arm/arch-ebsa110/time.h b/include/asm-arm/arch-ebsa110/time.h
index 278c8e3632a1..30c90e607546 100644
--- a/include/asm-arm/arch-ebsa110/time.h
+++ b/include/asm-arm/arch-ebsa110/time.h
@@ -17,17 +17,80 @@
  */
 
 #include <asm/leds.h>
+#include <asm/io.h>
 
-extern int  ebsa110_reset_timer(void);
-extern void ebsa110_setup_timer(void);
+extern unsigned long (*gettimeoffset)(void);
+
+#define PIT_CTRL		(PIT_BASE + 0x0d)
+#define PIT_T2			(PIT_BASE + 0x09)
+#define PIT_T1			(PIT_BASE + 0x05)
+#define PIT_T0			(PIT_BASE + 0x01)
+
+/*
+ * This is the rate at which your MCLK signal toggles (in Hz)
+ * This was measured on a 10 digit frequency counter sampling
+ * over 1 second.
+ */
+#define MCLK	47894000
+
+/*
+ * This is the rate at which the PIT timers get clocked
+ */
+#define CLKBY7	(MCLK / 7)
+
+/*
+ * This is the counter value.  We tick at 200Hz on this platform.
+ */
+#define COUNT	((CLKBY7 + (HZ / 2)) / HZ)
+
+/*
+ * Get the time offset from the system PIT.  Note that if we have missed an
+ * interrupt, then the PIT counter will roll over (ie, be negative).
+ * This actually works out to be convenient.
+ */
+static unsigned long ebsa110_gettimeoffset(void)
+{
+	unsigned long offset, count;
+
+	__raw_writeb(0x40, PIT_CTRL);
+	count = __raw_readb(PIT_T1);
+	count |= __raw_readb(PIT_T1) << 8;
+
+	/*
+	 * If count > COUNT, make the number negative.
+	 */
+	if (count > COUNT)
+		count |= 0xffff0000;
+
+	offset = COUNT;
+	offset -= count;
+
+	/*
+	 * `offset' is in units of timer counts.  Convert
+	 * offset to units of microseconds.
+	 */
+	offset = offset * (1000000 / HZ) / COUNT;
+
+	return offset;
+}
 
 static void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 {
-	if (ebsa110_reset_timer()) {
-		do_leds();
-		do_timer(regs);
-		do_profile(regs);
-	}
+	u32 count;
+
+	/* latch and read timer 1 */
+	__raw_writeb(0x40, PIT_CTRL);
+	count = __raw_readb(PIT_T1);
+	count |= __raw_readb(PIT_T1) << 8;
+
+	count += COUNT;
+
+	__raw_writeb(count & 0xff, PIT_T1);
+	__raw_writeb(count >> 8, PIT_T1);
+
+	do_leds();
+	do_timer(regs);
+	do_profile(regs);
 }
 
 /*
@@ -35,7 +98,14 @@ static void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  */
 void __init time_init(void)
 {
-	ebsa110_setup_timer();
+	/*
+	 * Timer 1, mode 2, LSB/MSB
+	 */
+	__raw_writeb(0x70, PIT_CTRL);
+	__raw_writeb(COUNT & 0xff, PIT_T1);
+	__raw_writeb(COUNT >> 8, PIT_T1);
+
+	gettimeoffset = ebsa110_gettimeoffset;
 
 	timer_irq.handler = timer_interrupt;