Skip to content

Commit

Permalink
ledc: cleanup the clock selection code
Browse files Browse the repository at this point in the history
  • Loading branch information
@ginkgm @espressif-bot
ginkgm authored and espressif-bot committed Apr 14, 2022
1 parent 534346f commit d64c6f5
Showing 1 changed file with 68 additions and 58 deletions.
126 changes: 68 additions & 58 deletions components/driver/ledc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,8 @@ static __attribute__((unused)) const char *LEDC_TAG = "ledc";
#define LEDC_CHECK(a, str, ret_val) ESP_RETURN_ON_FALSE(a, ret_val, LEDC_TAG, "%s", str)
#define LEDC_ARG_CHECK(a, param) ESP_RETURN_ON_FALSE(a, ESP_ERR_INVALID_ARG, LEDC_TAG, param " argument is invalid")

#define LEDC_CLK_NOT_FOUND 0

typedef enum {
LEDC_FSM_IDLE,
LEDC_FSM_HW_FADE,
Expand Down Expand Up @@ -75,6 +77,11 @@ static __attribute__((unused)) const char *LEDC_FADE_INIT_ERROR_STR = "LEDC fade
//This value will be calibrated when in use.
static uint32_t s_ledc_slow_clk_8M = 0;

static const ledc_slow_clk_sel_t s_glb_clks[] = LEDC_LL_GLOBAL_CLOCKS;
#if SOC_LEDC_HAS_TIMER_SPECIFIC_MUX
static const struct { ledc_clk_src_t clk; uint32_t freq; } s_timer_specific_clks[] = LEDC_LL_TIMER_SPECIFIC_CLOCKS;
#endif

static void ledc_ls_timer_update(ledc_mode_t speed_mode, ledc_timer_t timer_sel)
{
if (speed_mode == LEDC_LOW_SPEED_MODE) {
Expand Down Expand Up @@ -341,52 +348,46 @@ static inline uint32_t ledc_calculate_divisor(uint32_t src_clk_freq, int freq_hz

static inline uint32_t ledc_auto_global_clk_divisor(int freq_hz, uint32_t precision, ledc_slow_clk_sel_t* clk_target)
{
uint32_t div_param = 0;
uint32_t i = 0;
uint32_t ret = LEDC_CLK_NOT_FOUND;
uint32_t clk_freq = 0;

/* This function will go through all the following clock sources to look
* for a valid divisor which generates the requested frequency. */
const ledc_slow_clk_sel_t glb_clks[] = LEDC_LL_GLOBAL_CLOCKS;

for (i = 0; i < DIM(glb_clks); i++) {
for (int i = 0; i < DIM(s_glb_clks); i++) {
/* Before calculating the divisor, we need to have the RTC frequency.
* If it hasn't been measured yet, try calibrating it now. */
if (glb_clks[i] == LEDC_SLOW_CLK_RTC8M && s_ledc_slow_clk_8M == 0 && !ledc_slow_clk_calibrate()) {
if (s_glb_clks[i] == LEDC_SLOW_CLK_RTC8M && s_ledc_slow_clk_8M == 0 && !ledc_slow_clk_calibrate()) {
ESP_LOGD(LEDC_TAG, "Unable to retrieve RTC clock frequency, skipping it\n");
continue;
}

clk_freq = ledc_get_glb_clk_freq(glb_clks[i]);
div_param = ledc_calculate_divisor(clk_freq, freq_hz, precision);
clk_freq = ledc_get_glb_clk_freq(s_glb_clks[i]);
uint32_t div_param = ledc_calculate_divisor(clk_freq, freq_hz, precision);

/* If the divisor is valid, we can return this value. */
if (!LEDC_IS_DIV_INVALID(div_param)) {
*clk_target = glb_clks[i];
*clk_target = s_glb_clks[i];
ret = div_param;
break;
}
}

return div_param;

return ret;
}

#if SOC_LEDC_HAS_TIMER_SPECIFIC_MUX
static inline uint32_t ledc_auto_timer_specific_clk_divisor(ledc_mode_t speed_mode, int freq_hz, uint32_t precision,
ledc_clk_src_t* clk_source)
{
uint32_t div_param = 0;
uint32_t i = 0;

/* Use an anonymous structure, only this function requires it.
* Get the list of the timer-specific clocks, try to find one for the reuested frequency. */
const struct { ledc_clk_src_t clk; uint32_t freq; } specific_clks[] = LEDC_LL_TIMER_SPECIFIC_CLOCKS;
uint32_t ret = LEDC_CLK_NOT_FOUND;

for (i = 0; i < DIM(specific_clks); i++) {
div_param = ledc_calculate_divisor(specific_clks[i].freq, freq_hz, precision);
for (int i = 0; i < DIM(s_timer_specific_clks); i++) {
uint32_t div_param = ledc_calculate_divisor(s_timer_specific_clks[i].freq, freq_hz, precision);

/* If the divisor is valid, we can return this value. */
if (!LEDC_IS_DIV_INVALID(div_param)) {
*clk_source = specific_clks[i].clk;
*clk_source = s_timer_specific_clks[i].clk;
ret = div_param;
break;
}
}
Expand All @@ -395,17 +396,18 @@ static inline uint32_t ledc_auto_timer_specific_clk_divisor(ledc_mode_t speed_mo
/* On board that support LEDC high-speed mode, APB clock becomes a timer-
* specific clock when in high speed mode. Check if it is necessary here
* to test APB. */
if (speed_mode == LEDC_HIGH_SPEED_MODE && i == DIM(specific_clks)) {
if (speed_mode == LEDC_HIGH_SPEED_MODE && ret == LEDC_CLK_NOT_FOUND) {
/* No divider was found yet, try with APB! */
div_param = ledc_calculate_divisor(esp_clk_apb_freq(), freq_hz, precision);
uint32_t div_param = ledc_calculate_divisor(esp_clk_apb_freq(), freq_hz, precision);

if (!LEDC_IS_DIV_INVALID(div_param)) {
*clk_source = LEDC_APB_CLK;
ret = div_param;
}
}
#endif

return div_param;
return ret;
}
#endif

Expand All @@ -416,27 +418,31 @@ static inline uint32_t ledc_auto_timer_specific_clk_divisor(ledc_mode_t speed_mo
static uint32_t ledc_auto_clk_divisor(ledc_mode_t speed_mode, int freq_hz, uint32_t precision,
ledc_clk_src_t* clk_source, ledc_slow_clk_sel_t* clk_target)
{
uint32_t div_param = 0;
uint32_t ret = LEDC_CLK_NOT_FOUND;

#if SOC_LEDC_HAS_TIMER_SPECIFIC_MUX
/* If the SoC presents timer-specific clock(s), try to achieve the given frequency
* thanks to it/them.
* clk_source parameter will returned by this function. */
div_param = ledc_auto_timer_specific_clk_divisor(speed_mode, freq_hz, precision, clk_source);
uint32_t div_param_timer = ledc_auto_timer_specific_clk_divisor(speed_mode, freq_hz, precision, clk_source);

if (!LEDC_IS_DIV_INVALID(div_param)) {
if (div_param_timer != LEDC_CLK_NOT_FOUND) {
/* The dividor is valid, no need try any other clock, return directly. */
return div_param;
ret = div_param_timer;
}
#endif

/* On ESP32, only low speed channel can use the global clocks. For other
* chips, there are no high speed channels. */
if (speed_mode == LEDC_LOW_SPEED_MODE) {
div_param = ledc_auto_global_clk_divisor(freq_hz, precision, clk_target);
if (ret == LEDC_CLK_NOT_FOUND && speed_mode == LEDC_LOW_SPEED_MODE) {
uint32_t div_param_global = ledc_auto_global_clk_divisor(freq_hz, precision, clk_target);
if (div_param_global != LEDC_CLK_NOT_FOUND) {
*clk_source = LEDC_SCLK;
ret = div_param_global;
}
}

return div_param;
return ret;
}

static ledc_slow_clk_sel_t ledc_clk_cfg_to_global_clk(const ledc_clk_cfg_t clk_cfg)
Expand Down Expand Up @@ -483,17 +489,16 @@ static esp_err_t ledc_set_timer_div(ledc_mode_t speed_mode, ledc_timer_t timer_n
{
uint32_t div_param = 0;
const uint32_t precision = ( 0x1 << duty_resolution );
/* This variable represents the timer's mux value. It will be overwritten
* if a timer-specific clock is used. */
ledc_clk_src_t timer_clk_src = LEDC_SCLK;
/* Store the global clock */
/* The clock sources are not initialized on purpose. To produce compiler warning if used but the selector functions
* don't set them properly. */
/* Timer-specific mux. Set to timer-specific clock or LEDC_SCLK if a global clock is used. */
ledc_clk_src_t timer_clk_src;
/* Global clock mux. Should be set when LEDC_SCLK is used in LOW_SPEED_MODE. Otherwise left uninitialized. */
ledc_slow_clk_sel_t glb_clk;
uint32_t src_clk_freq = 0;

if (clk_cfg == LEDC_AUTO_CLK) {
/* User hasn't specified the speed, we should try to guess it. */
div_param = ledc_auto_clk_divisor(speed_mode, freq_hz, precision, &timer_clk_src, &glb_clk);

} else if (clk_cfg == LEDC_USE_RTC8M_CLK) {
/* User specified source clock(RTC8M_CLK) for low speed channel.
* Make sure the speed mode is correct. */
Expand All @@ -505,14 +510,16 @@ static esp_err_t ledc_set_timer_div(ledc_mode_t speed_mode, ledc_timer_t timer_n
goto error;
}

/* We have the RTC clock frequency now. */
div_param = ledc_calculate_divisor(s_ledc_slow_clk_8M, freq_hz, precision);

/* Set the global clock source */
timer_clk_src = LEDC_SCLK;
glb_clk = LEDC_SLOW_CLK_RTC8M;

/* We have the RTC clock frequency now. */
div_param = ledc_calculate_divisor(s_ledc_slow_clk_8M, freq_hz, precision);
if (LEDC_IS_DIV_INVALID(div_param)) {
div_param = LEDC_CLK_NOT_FOUND;
}
} else {

#if SOC_LEDC_HAS_TIMER_SPECIFIC_MUX
if (LEDC_LL_IS_TIMER_SPECIFIC_CLOCK(speed_mode, clk_cfg)) {
/* Currently we can convert a timer-specific clock to a source clock that
Expand All @@ -523,14 +530,18 @@ static esp_err_t ledc_set_timer_div(ledc_mode_t speed_mode, ledc_timer_t timer_n
} else
#endif
{
timer_clk_src = LEDC_SCLK;
glb_clk = ledc_clk_cfg_to_global_clk(clk_cfg);
}

src_clk_freq = ledc_get_src_clk_freq(clk_cfg);
uint32_t src_clk_freq = ledc_get_src_clk_freq(clk_cfg);
div_param = ledc_calculate_divisor(src_clk_freq, freq_hz, precision);
if (LEDC_IS_DIV_INVALID(div_param)) {
div_param = LEDC_CLK_NOT_FOUND;
}
}

if (LEDC_IS_DIV_INVALID(div_param)) {
if (div_param == LEDC_CLK_NOT_FOUND) {
goto error;
}

Expand All @@ -539,26 +550,24 @@ static esp_err_t ledc_set_timer_div(ledc_mode_t speed_mode, ledc_timer_t timer_n
timer_clk_src, (speed_mode == LEDC_LOW_SPEED_MODE ? "slow" : "fast"), div_param);

/* The following block configures the global clock.
* Thus, in theory, this only makes sense when the source clock is LEDC_SCLK
* and in LOW_SPEED_MODE (as HIGH_SPEED_MODE doesn't present any global clock)
*
* However, in practice, when the source clock is a timer-specific one (e.g.
* REF_TICK) and in LOW_SPEED_MODE, the global clock MUST be set to a
* specific one (APB_CLK). Therefore, in such case, the global clock also
* needs to be configured. In high-speed mode, this is not necessary.
* Thus, in theory, this only makes sense when configuring the LOW_SPEED timer and the source clock is LEDC_SCLK (as
* HIGH_SPEED timers won't be clocked by the global clock). However, there are some limitations due to HW design.
*/
if (speed_mode == LEDC_LOW_SPEED_MODE) {
if (timer_clk_src == LEDC_SCLK) {
ESP_LOGD(LEDC_TAG, "In slow speed mode, using clock %d", glb_clk);
} else {
#if SOC_LEDC_SUPPORT_APB_CLOCK
#if SOC_LEDC_HAS_TIMER_SPECIFIC_MUX
/* On ESP32 and ESP32-S2, when the source clock of LOW_SPEED timer is a timer-specific one (i.e. REF_TICK), the
* global clock MUST be set to APB_CLK. For HIGH_SPEED timers, this is not necessary.
*/
if (timer_clk_src != LEDC_SCLK) {
glb_clk = LEDC_SLOW_CLK_APB;
#elif SOC_LEDC_SUPPORT_PLL_DIV_CLOCK
/* Currently, code shouldn't reach here. timer_clk_src != LEDC_SCLK should only happen on esp32 and esp32s2, and
* PLL_DIV starts to replace APB as one of the global clock sources for some new chips. This is for future potential. */
glb_clk = LEDC_SLOW_CLK_PLL_DIV;
#endif
}
#else
/* On later chips, there is only one type of timer/channel (referred as LOW_SPEED in the code), which can only be
* clocked by the global clock. So there's no limitation on the global clock, except that it must be set.
*/
assert(timer_clk_src == LEDC_SCLK);
#endif
ESP_LOGD(LEDC_TAG, "In slow speed mode, global clk set: %d", glb_clk);

portENTER_CRITICAL(&ledc_spinlock);
ledc_hal_set_slow_clk_sel(&(p_ledc_obj[speed_mode]->ledc_hal), glb_clk);
Expand All @@ -571,6 +580,7 @@ static esp_err_t ledc_set_timer_div(ledc_mode_t speed_mode, ledc_timer_t timer_n
/* Reset the timer. */
ledc_timer_rst(speed_mode, timer_num);
return ESP_OK;

error:
ESP_LOGE(LEDC_TAG, "requested frequency and duty resolution can not be achieved, try reducing freq_hz or duty_resolution. div_param=%d",
(uint32_t ) div_param);
Expand Down

0 comments on commit d64c6f5

Please sign in to comment.