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Subject[PATCH 2/4] RISC-V: Support per-hart timebase-frequency
Date
Follow the updated DT specs and read the timebase-frequency
from the boot cpu. Keep the old DT reading as well for backward
compatibility. This patch is rework of old patch from Palmer.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
arch/riscv/kernel/time.c | 9 +--------
drivers/clocksource/riscv_timer.c | 22 ++++++++++++++++++++++
2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/arch/riscv/kernel/time.c b/arch/riscv/kernel/time.c
index 1911c8f6..225fe743 100644
--- a/arch/riscv/kernel/time.c
+++ b/arch/riscv/kernel/time.c
@@ -20,14 +20,7 @@ unsigned long riscv_timebase;

void __init time_init(void)
{
- struct device_node *cpu;
- u32 prop;
-
- cpu = of_find_node_by_path("/cpus");
- if (!cpu || of_property_read_u32(cpu, "timebase-frequency", &prop))
- panic(KERN_WARNING "RISC-V system with no 'timebase-frequency' in DTS\n");
- riscv_timebase = prop;
+ timer_probe();

lpj_fine = riscv_timebase / HZ;
- timer_probe();
}
diff --git a/drivers/clocksource/riscv_timer.c b/drivers/clocksource/riscv_timer.c
index 084e97dc..96af7058 100644
--- a/drivers/clocksource/riscv_timer.c
+++ b/drivers/clocksource/riscv_timer.c
@@ -83,6 +83,26 @@ void riscv_timer_interrupt(void)
evdev->event_handler(evdev);
}

+static long __init riscv_timebase_frequency(struct device_node *node)
+{
+ u32 timebase;
+
+ if (!of_property_read_u32(node, "timebase-frequency", &timebase))
+ return timebase;
+
+ /*
+ * As per the DT specification, timebase-frequency should be present
+ * under individual cpu node. Unfortunately, there are already available
+ * HiFive Unleashed devices where the timebase-frequency entry is under
+ * CPUs. check under parent "cpus" node to cover those devices.
+ */
+ if (!of_property_read_u32(node->parent, "timebase-frequency",
+ &timebase))
+ return timebase;
+
+ panic("RISC-V system with no 'timebase-frequency' in DTS\n");
+}
+
static int __init riscv_timer_init_dt(struct device_node *n)
{
int cpuid, hartid, error;
@@ -94,6 +114,8 @@ static int __init riscv_timer_init_dt(struct device_node *n)
if (cpuid != smp_processor_id())
return 0;

+ /* This should be called only for boot cpu */
+ riscv_timebase = riscv_timebase_frequency(n);
cs = per_cpu_ptr(&riscv_clocksource, cpuid);
clocksource_register_hz(cs, riscv_timebase);

--
2.7.4
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