[PATCH v2] arm: zynq: Fix system clock with multi_v7_defconfig
Ola Jeppsson
ola at adapteva.com
Sun Mar 22 18:39:38 PDT 2015
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 at adapteva.com>
---
arch/arm/mach-zynq/common.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/arch/arm/mach-zynq/common.c b/arch/arm/mach-zynq/common.c
index c887196..a4666d4 100644
--- a/arch/arm/mach-zynq/common.c
+++ b/arch/arm/mach-zynq/common.c
@@ -148,10 +148,36 @@ out:
platform_device_register_full(&devinfo);
}
+#if defined(CONFIG_CPU_FREQ) && defined(CONFIG_ARM_GLOBAL_TIMER)
+static struct property zynq_disable_arm_global_timer_prop = {
+ .name = "status",
+ .length = sizeof("disabled"),
+ .value = "disabled"
+};
+
+static void __init zynq_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__);
+}
+#endif
+
static void __init zynq_timer_init(void)
{
zynq_early_slcr_init();
+#if defined(CONFIG_CPU_FREQ) && defined(CONFIG_ARM_GLOBAL_TIMER)
+ zynq_disable_arm_global_timer();
+#endif
zynq_clock_init();
of_clk_init(NULL);
clocksource_of_init();
--
2.3.3
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