[ltt-dev] LTT for ARM

[Mathieu Desnoyers]

* Ali Günhan Akyürek (aliakyurek at gmail.com) wrote:
> Hi all,
> 
> Two years ago, I've integrated LTTng to a device with ARM platform and with
> kernel 2.6.22. LTTng version was 0.9.10.
> I used a sub-arch specific clock source for timestamps, based on the
> discussion below:
> 
> http://lttng.org/pipermail/ltt-dev/2009-January/000771.html
> 
> My sub-arch specific code in asm-arm/ltt.h was the following:
> 
> +#ifndef _ASM_ARM_LTT_H
> +#define _ASM_ARM_LTT_H
> +
> +#include <linux/jiffies.h>
> +#include <linux/seqlock.h>
> +
> +#define LTT_ARCH_TYPE LTT_ARCH_TYPE_ARM
> +#define LTT_ARCH_VARIANT LTT_ARCH_VARIANT_NONE
> +
> +#define DEV_MEM_READ_LE(addr)  ((*((volatile unsigned int*)(addr))))
> +
> +#define SOCTIMER1_VAL_REG 0xF102031C
> +#define TIMER1_VAL ((0xffffffff - DEV_MEM_READ_LE(SOCTIMER1_VAL_REG)))
> +
> +#define TCLK_200MHZ    200000000
> +
> +u64 ltt_heartbeat_read_synthetic_tsc(void);
> +#undef LTT_HAS_TSC
> +
> +
> +static inline u32 ltt_get_timestamp32(void)
> +{
> +    return TIMER1_VAL;
> +}
> +
> +/* The shift overflow doesn't matter */
> +static inline u64 ltt_get_timestamp64(void)
> +{
> +    return ltt_heartbeat_read_synthetic_tsc();
> +}
> +
> +/* this has to be called with the write seqlock held */
> +static inline void ltt_reset_timestamp(void)
> +{
> +    //atomic_set(&lttng_logical_clock, 0);
> +}
> +
> +
> +static inline unsigned int ltt_frequency(void)
> +{
> +    return TCLK_200MHZ;    //number of timer ticks in a second.
> +}
> +
> +
> +static inline u32 ltt_freq_scale(void)
> +{
> +  return 1;
> +}
> 
> This worked great for me at that time. However as today, I have to use
> kernel 2.6.31 and LTTng 0.178 on same device.
> Now, nor asm-arm/ltt.h, neither ltt_get_timestamp32 function exists. How
> must I proceed?
> Thanks in advance.

The best way to understand the ARM trace clock is to look at the lttng
"development snapshot" patchset, which includes the LTTng trace clocks
patches all folded into about one patch per architecture. See

http://lists.casi.polymtl.ca/pipermail/ltt-dev/2011-January/003751.html

Once you see how the trace clock code works, and how to create your own
patch to add your own support, you can then move to the "lttng stable"
tree, which are still the versions you should use as an end user (until
we complete the current development phase).

Thanks,

Mathieu

> 
> Best regards,
> Ali

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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com