[PATCH] bsp/tms570: implemented and tested initialization of Cortex-R performance counters.

[Joel Sherrill]

Pushed.

Followups can just be subsequent patches.

On 8/22/2014 10:20 AM, Pavel Pisa wrote:
> The code is written as BSP specific now but it should work for all
> Cortex-A and R based CPUs and can be moved to ARM generic place in future.
>
> StackOverflow suggested sequences of writes to the registers required
> to start counters is used.
>
> http://stackoverflow.com/questions/3247373/how-to-measure-program-execution-time-in-arm-cortex-a8-processor
> ---
>  c/src/lib/libbsp/arm/tms570/misc/cpucounterread.c | 88 +++++++++++++++++++++--
>  1 file changed, 84 insertions(+), 4 deletions(-)
>
> diff --git a/c/src/lib/libbsp/arm/tms570/misc/cpucounterread.c b/c/src/lib/libbsp/arm/tms570/misc/cpucounterread.c
> index f25380c..3ce2f63 100644
> --- a/c/src/lib/libbsp/arm/tms570/misc/cpucounterread.c
> +++ b/c/src/lib/libbsp/arm/tms570/misc/cpucounterread.c
> @@ -3,7 +3,14 @@
>   *
>   * @ingroup tms570_clocks
>   *
> - * @brief System clocks.
> + * @brief Cortex-R performace counters
> + *
> + * The counters setup functions are these which has been suggested
> + * on StackOverflow
> + *
> + * Code is probably for use on Cortex-A without modifications as well.
> + *
> + * http://stackoverflow.com/questions/3247373/how-to-measure-program-execution-time-in-arm-cortex-a8-processor
>   */
>  
>  /*
> @@ -14,9 +21,6 @@
>   * 166 36 Praha 6
>   * Czech Republic
>   *
> - * Based on LPC24xx and LPC1768 BSP
> - * by embedded brains GmbH and others
> - *
>   * The license and distribution terms for this file may be
>   * found in the file LICENSE in this distribution or at
>   * http://www.rtems.org/license/LICENSE.
> @@ -27,6 +31,79 @@
>  #include <rtems.h>
>  #include <bsp.h>
>  
> +static int cpu_counter_initialized;
> +
> +
> +/**
> + * @brief set mode of Cortex-R performance counters
> + *
> + * Based on example found on http://stackoverflow.com
> + *
> + * @param[in] do_reset if set, values of the counters are reset
> + * @param[in] enable_divider if set, CCNT counts clocks divided by 64
> + * @retval Void
> + */
> +static inline void _CPU_Counter_init_perfcounters(
> +    int32_t do_reset,
> +    int32_t enable_divider
> +)
> +{
> +  /* in general enable all counters (including cycle counter) */
> +  int32_t value = 1;
> +
> +  /* peform reset */
> +  if (do_reset)
> +  {
> +    value |= 2;     /* reset all counters to zero */
> +    value |= 4;     /* reset cycle counter to zero */
> +  }
> +
> +  if (enable_divider)
> +    value |= 8;     /* enable "by 64" divider for CCNT */
> +
> +  value |= 16;
> +
> +  /* program the performance-counter control-register */
> +  asm volatile ("mcr p15, 0, %0, c9, c12, 0\t\n" :: "r"(value));
> +
> +  /* enable all counters */
> +  asm volatile ("mcr p15, 0, %0, c9, c12, 1\t\n" :: "r"(0x8000000f));
> +
> +  /* clear overflows */
> +  asm volatile ("mcr p15, 0, %0, c9, c12, 3\t\n" :: "r"(0x8000000f));
> +}
> +
> +/**
> + * @brief initialize Cortex-R performance counters subsystem
> + *
> + * Based on example found on http://stackoverflow.com
> + *
> + * @retval Void
> + *
> + */
> +static void _CPU_Counter_initialize(void)
> +{
> +  rtems_interrupt_level level;
> +
> +  rtems_interrupt_disable(level);
> +
> +  if ( cpu_counter_initialized ) {
> +    rtems_interrupt_enable(level);
> +    return;
> +  }
> +
> +  /* enable user-mode access to the performance counter */
> +  asm volatile ("mcr p15, 0, %0, c9, c14, 0\n\t" :: "r"(1));
> +
> +  /* disable counter overflow interrupts (just in case) */
> +  asm volatile ("mcr p15, 0, %0, c9, c14, 2\n\t" :: "r"(0x8000000f));
> +
> +  _CPU_Counter_init_perfcounters(false, false);
> +
> +  cpu_counter_initialized = 1;
> +
> +  rtems_interrupt_enable(level);
> +}
>  
>  /**
>   * @brief returns the actual value of Cortex-R cycle counter register
> @@ -39,6 +116,9 @@
>  CPU_Counter_ticks _CPU_Counter_read(void)
>  {
>    uint32_t ticks;
> +  if ( !cpu_counter_initialized ) {
> +    _CPU_Counter_initialize();
> +  }
>    asm volatile ("mrc p15, 0, %0, c9, c13, 0\n": "=r" (ticks));
>    return ticks;
>  }

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
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