[PATCH v18 06/15] clocksource/drivers/arm_arch_timer: Rework counter frequency detection.

fu.wei
2016-12-08T17:33:10Z

Currently, the counter frequency detection call(arch_timer_detect_rate)
combines all the ways to get counter frequency: device-tree property,
system coprocessor register, MMIO timer. But in the most of use cases,
we don't need all the ways to try:
For example, reading device-tree property will be needed only when
system boot with device-tree, getting frequency from MMIO timer register
will beneeded only when we init MMIO timer.

This patch separates paths to determine frequency:
Separate out device-tree code, keep them in device-tree init function.
Separate out the MMIO frequency and the sysreg frequency detection call,
and use the appropriate one for the counter.

Signed-off-by: Fu Wei <fu.wei@linaro.org>
Tested-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
---
drivers/clocksource/arm_arch_timer.c | 49 +++++++++++++++++++++++-------------
1 file changed, 31 insertions(+), 18 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index e43be0a..e554081 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -487,27 +487,31 @@ static int arch_timer_starting_cpu(unsigned int cpu)
return 0;
}

-static void
-arch_timer_detect_rate(void __iomem *cntbase, struct device_node *np)
+static void arch_timer_detect_rate(void)
{
- /* Who has more than one independent system counter? */
- if (arch_timer_rate)
- return;
+ /*
+ * Try to get the timer frequency from
+ * cntfrq_el0(system coprocessor register).
+ */
+ if (!arch_timer_rate)
+ arch_timer_rate = arch_timer_get_cntfrq();
+
+ /* Check the timer frequency. */
+ if (!arch_timer_rate)
+ pr_warn("frequency not available\n");
+}

+static void arch_timer_mem_detect_rate(void __iomem *cntbase)
+{
/*
- * Try to determine the frequency from the device tree or CNTFRQ,
- * if ACPI is enabled, get the frequency from CNTFRQ ONLY.
+ * Try to determine the frequency from
+ * CNTFRQ in memory-mapped timer.
*/
- if (!acpi_disabled ||
- of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) {
- if (cntbase)
- arch_timer_rate = readl_relaxed(cntbase + CNTFRQ);
- else
- arch_timer_rate = arch_timer_get_cntfrq();
- }
+ if (!arch_timer_rate)
+ arch_timer_rate = readl_relaxed(cntbase + CNTFRQ);

/* Check the timer frequency. */
- if (arch_timer_rate == 0)
+ if (!arch_timer_rate)
pr_warn("frequency not available\n");
}

@@ -883,7 +887,9 @@ static int __init arch_timer_of_init(struct device_node *np)
for (i = ARCH_TIMER_PHYS_SECURE_PPI; i < ARCH_TIMER_MAX_TIMER_PPI; i++)
arch_timer_ppi[i] = irq_of_parse_and_map(np, i);

- arch_timer_detect_rate(NULL, np);
+ if (!arch_timer_rate &&
+ of_property_read_u32(np, "clock-frequency", &arch_timer_rate))
+ arch_timer_detect_rate();

arch_timer_c3stop = !of_property_read_bool(np, "always-on");

@@ -986,7 +992,14 @@ static int __init arch_timer_mem_init(struct device_node *np)
goto out;
}

- arch_timer_detect_rate(base, np);
+ /*
+ * Try to determine the frequency from the device tree,
+ * if fail, get the frequency from CNTFRQ.
+ */
+ if (!arch_timer_rate &&
+ of_property_read_u32(np, "clock-frequency", &arch_timer_rate))
+ arch_timer_mem_detect_rate(base);
+
ret = arch_timer_mem_register(base, irq);
if (ret)
goto out;
@@ -1048,7 +1061,7 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table)
gtdt->non_secure_el2_flags);

/* Get the frequency from CNTFRQ */
- arch_timer_detect_rate(NULL, NULL);
+ arch_timer_detect_rate();

arch_timer_uses_ppi = arch_timer_select_ppi();
if (!arch_timer_ppi[arch_timer_uses_ppi]) {
--
2.9.3