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SAMV7-XULT: If Tickless mode is selected then enabled PCK6 as a timer/counter clock source

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This commit is contained in:
Gregory Nutt 2015-12-04 10:53:34 -06:00
parent 1f17ba860a
commit 2e8e851d99
1 changed files with 36 additions and 0 deletions
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36
configs/samv71-xult/src/sam_boot.c
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@ -39,13 +39,18 @@
#include <nuttx/config.h>
#include <stdint.h>
#include <stdbool.h>
#include <assert.h>
#include <debug.h>
#include <nuttx/board.h>
#include <nuttx/clock.h>
#include <arch/board/board.h>
#include "up_arch.h"
#include "sam_start.h"
#include "sam_pck.h"
#include "samv71-xult.h"
/****************************************************************************
@ -73,6 +78,37 @@
void sam_boardinitialize(void)
{
#ifdef CONFIG_SCHED_TICKLESS
uint32_t frequency;
uint32_t actual;
/* If Tickless mode is selected then enabled PCK6 as a possible clock
* source for the timer/counters. The ideal frequency could be:
*
* frequency = 1,000,000 / CONFIG_USEC_PER_TICK
*
* The main crystal is selected as the frequency source. The maximum
* prescaler value is 256 so the minimum frequency is 46,875 Hz which
* corresponds to a period of 21.3 microseconds. A value of
* CONFIG_USEC_PER_TICK=20, or 50KHz, would give an exact solution with
* a divider of 240.
*/
frequency = USEC_PER_SEC / CONFIG_USEC_PER_TICK;
DEBUGASSERT(frequency >= (BOARD_MAINOSC_FREQUENCY / 256));
actual = sam_pck_configure(PCK6, PCKSRC_MAINCK, frequency);
/* We expect to achieve this frequency exactly */
DEBUGASSERT(actual == frequency);
UNUSED(actual);
/* Enable PCK6 */
(void)sam_pck_enable(PCK6, true);
#endif
#ifdef CONFIG_SAMV7_SDRAMC
/* Configure SDRAM if it has been enabled in the NuttX configuration.
* Here we assume, of course, that we are not running out SDRAM.