[PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework counter frequency detection.

fu.wei
2017-01-18T13:25:32Z

From: Fu Wei <fu.wei@linaro.org>

The counter frequency detection call(arch_timer_detect_rate) combines two
ways to get counter frequency: system coprocessor register and MMIO timer.
But in a specific timer init code, we only need one way to try:
getting frequency from MMIO timer register will be needed only when we
init MMIO timer; getting frequency from system coprocessor register will
be needed only when we init arch timer.

This patch separates paths to determine frequency:
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>
---
drivers/clocksource/arm_arch_timer.c | 40 ++++++++++++++++++++++--------------
1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 6484f84..9482481 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -488,23 +488,33 @@ static int arch_timer_starting_cpu(unsigned int cpu)
return 0;
}

-static void arch_timer_detect_rate(void __iomem *cntbase)
+static void __arch_timer_determine_rate(u32 rate)
{
- /* Who has more than one independent system counter? */
- if (arch_timer_rate)
- return;
+ /* Check the timer frequency. */
+ if (!arch_timer_rate) {
+ if (rate)
+ arch_timer_rate = rate;
+ else
+ pr_warn("frequency not available\n");
+ } else if (rate && arch_timer_rate != rate) {
+ pr_warn("got different frequency, keep original.\n");
+ }
+}

+static void arch_timer_detect_rate(void)
+{
/*
- * Try to determine the frequency from the MMIO timer or the sysreg.
+ * Try to get the timer frequency from the sysreg CNTFRQ.
*/
- if (cntbase)
- arch_timer_rate = readl_relaxed(cntbase + CNTFRQ);
- else
- arch_timer_rate = arch_timer_get_cntfrq();
+ __arch_timer_determine_rate(arch_timer_get_cntfrq());
+}

- /* Check the timer frequency. */
- if (arch_timer_rate == 0)
- pr_warn("frequency not available\n");
+static void arch_timer_mem_detect_rate(void __iomem *cntbase)
+{
+ /*
+ * Try to get the timer frequency from the CNTFRQ reg of MMIO timer.
+ */
+ __arch_timer_determine_rate(readl_relaxed(cntbase + CNTFRQ));
}

static void arch_timer_banner(unsigned type)
@@ -887,7 +897,7 @@ static int __init arch_timer_of_init(struct device_node *np)
*/
if (!arch_timer_rate &&
of_property_read_u32(np, "clock-frequency", &arch_timer_rate))
- arch_timer_detect_rate(NULL);
+ arch_timer_detect_rate();

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

@@ -1001,7 +1011,7 @@ static int __init arch_timer_mem_init(struct device_node *np)
*/
if (!arch_timer_rate &&
of_property_read_u32(np, "clock-frequency", &arch_timer_rate))
- arch_timer_detect_rate(base);
+ arch_timer_mem_detect_rate(base);

ret = arch_timer_mem_register(base, irq);
if (ret)
@@ -1064,7 +1074,7 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table)
gtdt->non_secure_el2_flags);

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

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