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Diffstat (limited to 'arch/arm/mach-omap2/timer.c')
-rw-r--r--arch/arm/mach-omap2/timer.c44
1 files changed, 38 insertions, 6 deletions
diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
index 4f61148ec168..7d45c84c69ba 100644
--- a/arch/arm/mach-omap2/timer.c
+++ b/arch/arm/mach-omap2/timer.c
@@ -54,6 +54,7 @@
#include "soc.h"
#include "common.h"
+#include "control.h"
#include "powerdomain.h"
#include "omap-secure.h"
@@ -496,7 +497,8 @@ static void __init realtime_counter_init(void)
void __iomem *base;
static struct clk *sys_clk;
unsigned long rate;
- unsigned int reg, num, den;
+ unsigned int reg;
+ unsigned long long num, den;
base = ioremap(REALTIME_COUNTER_BASE, SZ_32);
if (!base) {
@@ -511,13 +513,42 @@ static void __init realtime_counter_init(void)
}
rate = clk_get_rate(sys_clk);
+
+ if (soc_is_dra7xx()) {
+ /*
+ * Errata i856 says the 32.768KHz crystal does not start at
+ * power on, so the CPU falls back to an emulated 32KHz clock
+ * based on sysclk / 610 instead. This causes the master counter
+ * frequency to not be 6.144MHz but at sysclk / 610 * 375 / 2
+ * (OR sysclk * 75 / 244)
+ *
+ * This affects at least the DRA7/AM572x 1.0, 1.1 revisions.
+ * Of course any board built without a populated 32.768KHz
+ * crystal would also need this fix even if the CPU is fixed
+ * later.
+ *
+ * Either case can be detected by using the two speedselect bits
+ * If they are not 0, then the 32.768KHz clock driving the
+ * coarse counter that corrects the fine counter every time it
+ * ticks is actually rate/610 rather than 32.768KHz and we
+ * should compensate to avoid the 570ppm (at 20MHz, much worse
+ * at other rates) too fast system time.
+ */
+ reg = omap_ctrl_readl(DRA7_CTRL_CORE_BOOTSTRAP);
+ if (reg & DRA7_SPEEDSELECT_MASK) {
+ num = 75;
+ den = 244;
+ goto sysclk1_based;
+ }
+ }
+
/* Numerator/denumerator values refer TRM Realtime Counter section */
switch (rate) {
- case 1200000:
+ case 12000000:
num = 64;
den = 125;
break;
- case 1300000:
+ case 13000000:
num = 768;
den = 1625;
break;
@@ -529,11 +560,11 @@ static void __init realtime_counter_init(void)
num = 192;
den = 625;
break;
- case 2600000:
+ case 26000000:
num = 384;
den = 1625;
break;
- case 2700000:
+ case 27000000:
num = 256;
den = 1125;
break;
@@ -545,6 +576,7 @@ static void __init realtime_counter_init(void)
break;
}
+sysclk1_based:
/* Program numerator and denumerator registers */
reg = readl_relaxed(base + INCREMENTER_NUMERATOR_OFFSET) &
NUMERATOR_DENUMERATOR_MASK;
@@ -556,7 +588,7 @@ static void __init realtime_counter_init(void)
reg |= den;
writel_relaxed(reg, base + INCREMENTER_DENUMERATOR_RELOAD_OFFSET);
- arch_timer_freq = (rate / den) * num;
+ arch_timer_freq = DIV_ROUND_UP_ULL(rate * num, den);
set_cntfreq();
iounmap(base);