alex/esp-idf
1
0
Fork 0
mirror of https://github.com/espressif/esp-idf.git synced 2025-08-08 04:02:27 +00:00
Code Issues Packages Projects Releases Wiki Activity

esp_timer, hal: add support for non-integer systimer frequency

Browse Source 
When ESP32-C2 is paired with a 26 MHz XTAL, the systimer tick
frequency becomes equal to 26 / 2.5 = 10.4 MHz. Previously we always
assumed that systimer tick frequency is integer (and 1 MHz * power of
two, above that!).
This commit introduces a new LL macro, SYSTIMER_LL_TICKS_PER_US_DIV.
It should be set in such a way that:

1. SYSTIMER_LL_TICKS_PER_US / SYSTIMER_LL_TICKS_PER_US_DIV equals the
   actual systimer tick frequency,
2. and SYSTIMER_LL_TICKS_PER_US is integer.

For ESP32-C2 this means that SYSTIMER_LL_TICKS_PER_US = 52 and
SYSTIMER_LL_TICKS_PER_US_DIV = 5.

This introduced two possible issues:

1. Overflow when multiplying systimer counter by 5
   - Should not be an issue, since systimer counter is 52-bit, so
     counter * 5 is no more than 55-bit.
2. The code needs to perform:
   - divide by 5: when converting from microseconds to ticks
   - divide by 52: when converting from ticks to microseconds
   The latter potentially introduces a performance issue for the
   esp_timer_get_time function.
This commit is contained in:
Ivan Grokhotkov
2022-07-01 19:58:23 +02:00
committed by songruojing
parent f0f9890096
commit 5b54ae76d4
17 changed files with 102 additions and 113 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
components/esp_timer/src/esp_timer_impl_systimer.c
View File

@@ -64,7 +64,7 @@ uint64_t IRAM_ATTR esp_timer_impl_get_counter_reg(void)
int64_t IRAM_ATTR esp_timer_impl_get_time(void)
{
return systimer_hal_get_counter_value(&systimer_hal, SYSTIMER_LL_COUNTER_CLOCK) / SYSTIMER_LL_TICKS_PER_US;
return systimer_hal_get_counter_value(&systimer_hal, SYSTIMER_LL_COUNTER_CLOCK) * SYSTIMER_LL_TICKS_PER_US_DIV / SYSTIMER_LL_TICKS_PER_US;
}
int64_t esp_timer_get_time(void) __attribute__((alias("esp_timer_impl_get_time")));
@@ -96,7 +96,7 @@ static void IRAM_ATTR timer_alarm_isr(void *arg)
void IRAM_ATTR esp_timer_impl_update_apb_freq(uint32_t apb_ticks_per_us)
{
#if !SOC_SYSTIMER_FIXED_TICKS_US
#if !SOC_SYSTIMER_HAS_FIXED_TICKS_PER_US
systimer_hal_on_apb_freq_update(&systimer_hal, apb_ticks_per_us);
#endif
}
@@ -104,7 +104,9 @@ void IRAM_ATTR esp_timer_impl_update_apb_freq(uint32_t apb_ticks_per_us)
void esp_timer_impl_set(uint64_t new_us)
{
portENTER_CRITICAL_SAFE(&s_time_update_lock);
systimer_counter_value_t new_count = { .val = new_us * SYSTIMER_LL_TICKS_PER_US };
systimer_counter_value_t new_count = {
.val = new_us * SYSTIMER_LL_TICKS_PER_US / SYSTIMER_LL_TICKS_PER_US_DIV
};
systimer_ll_set_counter_value(systimer_hal.dev, SYSTIMER_LL_COUNTER_CLOCK, new_count.val);
systimer_ll_apply_counter_value(systimer_hal.dev, SYSTIMER_LL_COUNTER_CLOCK);
portEXIT_CRITICAL_SAFE(&s_time_update_lock);
@@ -121,7 +123,7 @@ esp_err_t esp_timer_impl_early_init(void)
{
systimer_hal_init(&systimer_hal);
#if !SOC_SYSTIMER_FIXED_TICKS_US
#if !SOC_SYSTIMER_HAS_FIXED_TICKS_PER_US
assert(esp_clk_xtal_freq() == (40 * 1000000) &&
"update the step for xtal to support other XTAL:APB frequency ratios");
systimer_hal_set_steps_per_tick(&systimer_hal, 0, 2); // for xtal