[PATCH v16 07/15] clocksource/drivers/arm_arch_timer: Refactor arch_timer_detect_rate to keep dt code in *_of_init

From: fu . wei
Date: Wed Nov 16 2016 - 08:53:03 EST


From: Fu Wei <fu.wei@xxxxxxxxxx>

The patch refactor original arch_timer_detect_rate function:
(1) Separate out device-tree code, keep them in device-tree init
function:
arch_timer_of_init,
arch_timer_mem_init;
(2) Improve original mechanism, if getting from memory-mapped timer
fail, try arch_timer_get_cntfrq() again.

Signed-off-by: Fu Wei <fu.wei@xxxxxxxxxx>
---
drivers/clocksource/arm_arch_timer.c | 45 +++++++++++++++++++++++-------------
1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index af22953..fe4e812 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 __iomem *cntbase)
{
/* Who has more than one independent system counter? */
if (arch_timer_rate)
return;
-
/*
- * Try to determine the frequency from the device tree or CNTFRQ,
- * if ACPI is enabled, get the frequency from CNTFRQ ONLY.
+ * If we got memory-mapped timer(cntbase != NULL),
+ * 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 (cntbase)
+ arch_timer_rate = readl_relaxed(cntbase + CNTFRQ);
+ /*
+ * Because in a system that implements both Secure and
+ * Non-secure states, CNTFRQ is only accessible in Secure state.
+ * So the operation above may fail, even if (cntbase != NULL),
+ * especially on ARM64.
+ * In this case, we can try cntfrq_el0(system coprocessor register).
+ */
+ if (!arch_timer_rate)
+ arch_timer_rate = arch_timer_get_cntfrq();
+ else
+ return;

/* 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(NULL);

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

@@ -983,7 +989,14 @@ 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_detect_rate(base);
+
ret = arch_timer_mem_register(base, irq);
if (ret)
goto out;
@@ -1046,7 +1059,7 @@ 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(NULL);

ret = arch_timer_uses_ppi_init();
if (ret)
--
2.7.4