+/*
+ * Where is the timer (VA)?
+ */
+#define TIMER0_VA_BASE IO_ADDRESS(VERSATILE_TIMER0_1_BASE)
+#define TIMER1_VA_BASE (IO_ADDRESS(VERSATILE_TIMER0_1_BASE) + 0x20)
+#define TIMER2_VA_BASE IO_ADDRESS(VERSATILE_TIMER2_3_BASE)
+#define TIMER3_VA_BASE (IO_ADDRESS(VERSATILE_TIMER2_3_BASE) + 0x20)
+#define VA_IC_BASE IO_ADDRESS(VERSATILE_VIC_BASE)
+
+/*
+ * How long is the timer interval?
+ */
+#define TIMER_INTERVAL (TICKS_PER_uSEC * mSEC_10)
+#if TIMER_INTERVAL >= 0x100000
+#define TIMER_RELOAD (TIMER_INTERVAL >> 8) /* Divide by 256 */
+#define TIMER_CTRL 0x88 /* Enable, Clock / 256 */
+#define TICKS2USECS(x) (256 * (x) / TICKS_PER_uSEC)
+#elif TIMER_INTERVAL >= 0x10000
+#define TIMER_RELOAD (TIMER_INTERVAL >> 4) /* Divide by 16 */
+#define TIMER_CTRL 0x84 /* Enable, Clock / 16 */
+#define TICKS2USECS(x) (16 * (x) / TICKS_PER_uSEC)
+#else
+#define TIMER_RELOAD (TIMER_INTERVAL)
+#define TIMER_CTRL 0x80 /* Enable */
+#define TICKS2USECS(x) ((x) / TICKS_PER_uSEC)
+#endif
+
+#define TIMER_CTRL_IE (1 << 5) /* Interrupt Enable */
+
+/*
+ * What does it look like?
+ */
+typedef struct TimerStruct {
+ unsigned long TimerLoad;
+ unsigned long TimerValue;
+ unsigned long TimerControl;
+ unsigned long TimerClear;
+} TimerStruct_t;
+
+extern unsigned long (*gettimeoffset)(void);
+
+/*
+ * Returns number of ms since last clock interrupt. Note that interrupts
+ * will have been disabled by do_gettimeoffset()
+ */
+static unsigned long versatile_gettimeoffset(void)
+{
+ volatile TimerStruct_t *timer0 = (TimerStruct_t *)TIMER0_VA_BASE;
+ unsigned long ticks1, ticks2, status;
+
+ /*
+ * Get the current number of ticks. Note that there is a race
+ * condition between us reading the timer and checking for
+ * an interrupt. We get around this by ensuring that the
+ * counter has not reloaded between our two reads.
+ */
+ ticks2 = timer0->TimerValue & 0xffff;
+ do {
+ ticks1 = ticks2;
+ status = __raw_readl(VA_IC_BASE + VIC_IRQ_RAW_STATUS);
+ ticks2 = timer0->TimerValue & 0xffff;
+ } while (ticks2 > ticks1);
+
+ /*
+ * Number of ticks since last interrupt.
+ */
+ ticks1 = TIMER_RELOAD - ticks2;
+
+ /*
+ * Interrupt pending? If so, we've reloaded once already.
+ *
+ * FIXME: Need to check this is effectively timer 0 that expires
+ */
+ if (status & IRQMASK_TIMERINT0_1)
+ ticks1 += TIMER_RELOAD;
+
+ /*
+ * Convert the ticks to usecs
+ */
+ return TICKS2USECS(ticks1);
+}
+
+/*
+ * IRQ handler for the timer
+ */
+static irqreturn_t versatile_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+ volatile TimerStruct_t *timer0 = (volatile TimerStruct_t *)TIMER0_VA_BASE;
+
+ // ...clear the interrupt
+ timer0->TimerClear = 1;
+
+ timer_tick(regs);
+
+ return IRQ_HANDLED;
+}
+
+static struct irqaction versatile_timer_irq = {
+ .name = "Versatile Timer Tick",
+ .flags = SA_INTERRUPT,
+ .handler = versatile_timer_interrupt
+};
+
+/*
+ * Set up timer interrupt, and return the current time in seconds.
+ */
+void __init versatile_init_time(void)
+{
+ volatile TimerStruct_t *timer0 = (volatile TimerStruct_t *)TIMER0_VA_BASE;
+ volatile TimerStruct_t *timer1 = (volatile TimerStruct_t *)TIMER1_VA_BASE;
+ volatile TimerStruct_t *timer2 = (volatile TimerStruct_t *)TIMER2_VA_BASE;
+ volatile TimerStruct_t *timer3 = (volatile TimerStruct_t *)TIMER3_VA_BASE;
+
+ /*
+ * set clock frequency:
+ * VERSATILE_REFCLK is 32KHz
+ * VERSATILE_TIMCLK is 1MHz
+ */
+ *(volatile unsigned int *)IO_ADDRESS(VERSATILE_SCTL_BASE) |=
+ ((VERSATILE_TIMCLK << VERSATILE_TIMER1_EnSel) | (VERSATILE_TIMCLK << VERSATILE_TIMER2_EnSel) |
+ (VERSATILE_TIMCLK << VERSATILE_TIMER3_EnSel) | (VERSATILE_TIMCLK << VERSATILE_TIMER4_EnSel));
+
+ /*
+ * Initialise to a known state (all timers off)
+ */
+ timer0->TimerControl = 0;
+ timer1->TimerControl = 0;
+ timer2->TimerControl = 0;
+ timer3->TimerControl = 0;
+
+ timer0->TimerLoad = TIMER_RELOAD;
+ timer0->TimerValue = TIMER_RELOAD;
+ timer0->TimerControl = TIMER_CTRL | 0x40 | TIMER_CTRL_IE; /* periodic + IE */
+
+ /*
+ * Make irqs happen for the system timer
+ */
+ setup_irq(IRQ_TIMERINT0_1, &versatile_timer_irq);
+ gettimeoffset = versatile_gettimeoffset;
+}
+