uint32_t NutClockGet(int idx)
{
if (clock_cache[idx] == 0) {
clock_cache[idx] = NutArchClockGet(idx) | NUT_CACHE_LVALID;
}
return clock_cache[idx] & ~NUT_CACHE_LVALID;
}
uint32_t NutGetCpuClock(void)
{
#ifdef NUT_CPU_FREQ
/* Keep this code small! Can we use a preprocessor
** macro to define NutGetCpuClock() as NUT_CPU_FREQ? */
return NUT_CPU_FREQ;
#else /* !NUT_CPU_FREQ */
/* Keep this code fast for the normal case, where the
** cached value is valid. */
if (clock_cache[NUT_HWCLK_CPU]) {
return clock_cache[NUT_HWCLK_CPU] & ~NUT_CACHE_LVALID;
}
#if NUT_HWCLK_MAX
return NutClockGet(NUT_HWCLK_CPU);
#else /* !NUT_HWCLK_MAX */
clock_cache[NUT_HWCLK_CPU] = NutArchClockGet(NUT_HWCLK_CPU) | NUT_CACHE_LVALID;
return clock_cache[NUT_HWCLK_CPU] & ~NUT_CACHE_LVALID;
#endif /* !NUT_HWCLK_MAX */
#endif /* !NUT_CPU_FREQ */
}
/*!
* \brief Get divider for a given MCI clock rate.
*
* \param clk Requested clock rate.
*/
static uint32_t At91MciClockDiv(uint32_t clk)
{
uint32_t rc;
/* MCI is driven by MCK/2. */
rc = NutArchClockGet(NUT_HWCLK_PERIPHERAL) / 2;
/* Compensate rounding error, but do not care about 10kHz. */
rc += clk - 10000;
/* Calculate the divider. */
rc /= clk;
/* Actual divider is 1 less, avoid underflow. */
if (rc) {
rc -= 1;
}
/* In reality, overflow will only happen when the caller requests
a unrealistic low MCI clock. */
if (rc > 255) {
rc = 255;
}
return rc;
}