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From: Jan Viktorin <viktorin@rehivetech.com>
To: Thomas Monjalon <thomas.monjalon@6wind.com>,
David Hunt <david.hunt@intel.com>, dev@dpdk.org
Date: Mon, 26 Oct 2015 17:37:27 +0100
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Subject: [dpdk-dev] [PATCH v2 05/16] eal/arm: implement rdtsc by PMU or
clock_gettime
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Enable to choose a preferred way to read timer based on the
configuration entry CONFIG_RTE_ARM_EAL_RDTSC_USE_PMU.
It requires a kernel module that is not included to work.
Based on the patch by David Hunt and Armuta Zende:
lib: added support for armv7 architecture
Signed-off-by: Jan Viktorin <viktorin@rehivetech.com>
Signed-off-by: Amruta Zende <amruta.zende@intel.com>
Signed-off-by: David Hunt <david.hunt@intel.com>
---
.../common/include/arch/arm/rte_cycles.h | 38 +++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/lib/librte_eal/common/include/arch/arm/rte_cycles.h b/lib/librte_eal/common/include/arch/arm/rte_cycles.h
index ff66ae2..5dcef25 100644
--- a/lib/librte_eal/common/include/arch/arm/rte_cycles.h
+++ b/lib/librte_eal/common/include/arch/arm/rte_cycles.h
@@ -54,8 +54,14 @@ extern "C" {
* @return
* The time base for this lcore.
*/
+#ifndef CONFIG_RTE_ARM_EAL_RDTSC_USE_PMU
+
+/**
+ * This call is easily portable to any ARM architecture, however,
+ * it may be damn slow and inprecise for some tasks.
+ */
static inline uint64_t
-rte_rdtsc(void)
+__rte_rdtsc_syscall(void)
{
struct timespec val;
uint64_t v;
@@ -67,6 +73,36 @@ rte_rdtsc(void)
v += (uint64_t) val.tv_nsec;
return v;
}
+#define rte_rdtsc __rte_rdtsc_syscall
+
+#else
+
+/**
+ * This function requires to configure the PMCCNTR and enable
+ * userspace access to it:
+ *
+ * asm volatile("mcr p15, 0, %0, c9, c14, 0" : : "r"(1));
+ * asm volatile("mcr p15, 0, %0, c9, c12, 0" : : "r"(29));
+ * asm volatile("mcr p15, 0, %0, c9, c12, 1" : : "r"(0x8000000f));
+ *
+ * which is possible only from the priviledged mode (kernel space).
+ */
+static inline uint64_t
+__rte_rdtsc_pmccntr(void)
+{
+ unsigned tsc;
+ uint64_t final_tsc;
+
+ /* Read PMCCNTR */
+ asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r"(tsc));
+ /* 1 tick = 64 clocks */
+ final_tsc = ((uint64_t)tsc) << 6;
+
+ return (uint64_t)final_tsc;
+}
+#define rte_rdtsc __rte_rdtsc_pmccntr
+
+#endif /* RTE_ARM_EAL_RDTSC_USE_PMU */
static inline uint64_t
rte_rdtsc_precise(void)
--
2.6.1