@@ -2,6 +2,10 @@
# Makefile for the linux kernel.
#
+ifeq ($(CONFIG_CPU_FREQ)-$(CONFIG_ARM_GLOBAL_TIMER), y-y)
+ CFLAGS_common.o += -DDISABLE_ARM_GLOBAL_TIMER
+endif
+
# Common support
obj-y := common.o slcr.o pm.o
obj-$(CONFIG_SMP) += headsmp.o platsmp.o
@@ -148,10 +148,38 @@ out:
platform_device_register_full(&devinfo);
}
+#ifdef DISABLE_ARM_GLOBAL_TIMER
+static struct property zynq_disable_arm_global_timer_prop = {
+ .name = "status",
+ .length = sizeof("disabled"),
+ .value = "disabled"
+};
+
+static void __init zynq_maybe_disable_arm_global_timer(void)
+{
+ struct device_node *np;
+
+ np = of_find_compatible_node(NULL, NULL, "arm,cortex-a9-global-timer");
+ if (!np)
+ return;
+
+ pr_info("%s: disabling arm_global_timer node\n", __func__);
+
+ if (of_update_property(np, &zynq_disable_arm_global_timer_prop))
+ pr_warn("%s: could not disable arm_global_timer node\n",
+ __func__);
+}
+#else
+static void __init zynq_maybe_disable_arm_global_timer(void)
+{
+}
+#endif
+
static void __init zynq_timer_init(void)
{
zynq_early_slcr_init();
+ zynq_maybe_disable_arm_global_timer();
zynq_clock_init();
of_clk_init(NULL);
clocksource_of_init();
As mentioned in this commit: arm: zynq: Don't use arm_global_timer with cpufreq 61f1fc7e9258a169ac8afb5ddf657a181e60d052 arm_global_timer depends on the CPU frequency. With cpufreq altering the CPU frequency arm_global_timer will not maintain a stable time base. So arm_global_timer must not be the clocksource when cpufreq is enabled. The above commit tries to solve this at build time by only selecting CONFIG_ARM_GLOBAL_TIMER if CONFIG_CPU_FREQ is disabled. This is not always sufficient because other machs can also enable CONFIG_ARM_GLOBAL_TIMER. Therefore: If built with CONFIG_CPU_FREQ and CONFIG_ARM_GLOBAL_TIMER, disable (on Zynq) the arm_global_timer devicetree node at boot before clock sources are initialized. This ensures that arm_global_timer will not be selected clocksource. Signed-off-by: Ola Jeppsson <ola@adapteva.com> --- arch/arm/mach-zynq/Makefile | 4 ++++ arch/arm/mach-zynq/common.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 32 insertions(+)