aboutsummaryrefslogtreecommitdiff
path: root/arch/ppc/platforms/chrp_time.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/ppc/platforms/chrp_time.c')
-rw-r--r--arch/ppc/platforms/chrp_time.c64
1 files changed, 63 insertions, 1 deletions
diff --git a/arch/ppc/platforms/chrp_time.c b/arch/ppc/platforms/chrp_time.c
index 29d074c305f..57753a55b58 100644
--- a/arch/ppc/platforms/chrp_time.c
+++ b/arch/ppc/platforms/chrp_time.c
@@ -163,13 +163,75 @@ unsigned long chrp_get_rtc_time(void)
return mktime(year, mon, day, hour, min, sec);
}
+/*
+ * Calibrate the decrementer frequency with the VIA timer 1.
+ */
+#define VIA_TIMER_FREQ_6 4700000 /* time 1 frequency * 6 */
+
+/* VIA registers */
+#define RS 0x200 /* skip between registers */
+#define T1CL (4*RS) /* Timer 1 ctr/latch (low 8 bits) */
+#define T1CH (5*RS) /* Timer 1 counter (high 8 bits) */
+#define T1LL (6*RS) /* Timer 1 latch (low 8 bits) */
+#define T1LH (7*RS) /* Timer 1 latch (high 8 bits) */
+#define ACR (11*RS) /* Auxiliary control register */
+#define IFR (13*RS) /* Interrupt flag register */
+
+/* Bits in ACR */
+#define T1MODE 0xc0 /* Timer 1 mode */
+#define T1MODE_CONT 0x40 /* continuous interrupts */
+
+/* Bits in IFR and IER */
+#define T1_INT 0x40 /* Timer 1 interrupt */
+
+static int __init chrp_via_calibrate_decr(void)
+{
+ struct device_node *vias;
+ volatile unsigned char __iomem *via;
+ int count = VIA_TIMER_FREQ_6 / 100;
+ unsigned int dstart, dend;
+
+ vias = find_devices("via-cuda");
+ if (vias == 0)
+ vias = find_devices("via");
+ if (vias == 0 || vias->n_addrs == 0)
+ return 0;
+ via = ioremap(vias->addrs[0].address, vias->addrs[0].size);
+
+ /* set timer 1 for continuous interrupts */
+ out_8(&via[ACR], (via[ACR] & ~T1MODE) | T1MODE_CONT);
+ /* set the counter to a small value */
+ out_8(&via[T1CH], 2);
+ /* set the latch to `count' */
+ out_8(&via[T1LL], count);
+ out_8(&via[T1LH], count >> 8);
+ /* wait until it hits 0 */
+ while ((in_8(&via[IFR]) & T1_INT) == 0)
+ ;
+ dstart = get_dec();
+ /* clear the interrupt & wait until it hits 0 again */
+ in_8(&via[T1CL]);
+ while ((in_8(&via[IFR]) & T1_INT) == 0)
+ ;
+ dend = get_dec();
+
+ tb_ticks_per_jiffy = (dstart - dend) / ((6 * HZ)/100);
+ tb_to_us = mulhwu_scale_factor(dstart - dend, 60000);
+
+ printk(KERN_INFO "via_calibrate_decr: ticks per jiffy = %u (%u ticks)\n",
+ tb_ticks_per_jiffy, dstart - dend);
+
+ iounmap(via);
+
+ return 1;
+}
void __init chrp_calibrate_decr(void)
{
struct device_node *cpu;
unsigned int freq, *fp;
- if (via_calibrate_decr())
+ if (chrp_via_calibrate_decr())
return;
/*