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

[fu . wei]

From: Fu Wei <fu....@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....@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