aboutsummaryrefslogtreecommitdiff
path: root/drivers/pwm
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/pwm')
-rw-r--r--drivers/pwm/pwm-stm32.c257
1 files changed, 257 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
index 2708212933f7..60bfc07c4912 100644
--- a/drivers/pwm/pwm-stm32.c
+++ b/drivers/pwm/pwm-stm32.c
@@ -8,6 +8,7 @@
* pwm-atmel.c from Bo Shen
*/
+#include <linux/bitfield.h>
#include <linux/mfd/stm32-timers.h>
#include <linux/module.h>
#include <linux/of.h>
@@ -25,6 +26,7 @@ struct stm32_pwm {
struct regmap *regmap;
u32 max_arr;
bool have_complementary_output;
+ u32 capture[4] ____cacheline_aligned; /* DMA'able buffer */
};
struct stm32_breakinput {
@@ -62,6 +64,258 @@ static int write_ccrx(struct stm32_pwm *dev, int ch, u32 value)
return -EINVAL;
}
+#define TIM_CCER_CC12P (TIM_CCER_CC1P | TIM_CCER_CC2P)
+#define TIM_CCER_CC12E (TIM_CCER_CC1E | TIM_CCER_CC2E)
+#define TIM_CCER_CC34P (TIM_CCER_CC3P | TIM_CCER_CC4P)
+#define TIM_CCER_CC34E (TIM_CCER_CC3E | TIM_CCER_CC4E)
+
+/*
+ * Capture using PWM input mode:
+ * ___ ___
+ * TI[1, 2, 3 or 4]: ........._| |________|
+ * ^0 ^1 ^2
+ * . . .
+ * . . XXXXX
+ * . . XXXXX |
+ * . XXXXX . |
+ * XXXXX . . |
+ * COUNTER: ______XXXXX . . . |_XXX
+ * start^ . . . ^stop
+ * . . . .
+ * v v . v
+ * v
+ * CCR1/CCR3: tx..........t0...........t2
+ * CCR2/CCR4: tx..............t1.........
+ *
+ * DMA burst transfer: | |
+ * v v
+ * DMA buffer: { t0, tx } { t2, t1 }
+ * DMA done: ^
+ *
+ * 0: IC1/3 snapchot on rising edge: counter value -> CCR1/CCR3
+ * + DMA transfer CCR[1/3] & CCR[2/4] values (t0, tx: doesn't care)
+ * 1: IC2/4 snapchot on falling edge: counter value -> CCR2/CCR4
+ * 2: IC1/3 snapchot on rising edge: counter value -> CCR1/CCR3
+ * + DMA transfer CCR[1/3] & CCR[2/4] values (t2, t1)
+ *
+ * DMA done, compute:
+ * - Period = t2 - t0
+ * - Duty cycle = t1 - t0
+ */
+static int stm32_pwm_raw_capture(struct stm32_pwm *priv, struct pwm_device *pwm,
+ unsigned long tmo_ms, u32 *raw_prd,
+ u32 *raw_dty)
+{
+ struct device *parent = priv->chip.dev->parent;
+ enum stm32_timers_dmas dma_id;
+ u32 ccen, ccr;
+ int ret;
+
+ /* Ensure registers have been updated, enable counter and capture */
+ regmap_update_bits(priv->regmap, TIM_EGR, TIM_EGR_UG, TIM_EGR_UG);
+ regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, TIM_CR1_CEN);
+
+ /* Use cc1 or cc3 DMA resp for PWM input channels 1 & 2 or 3 & 4 */
+ dma_id = pwm->hwpwm < 2 ? STM32_TIMERS_DMA_CH1 : STM32_TIMERS_DMA_CH3;
+ ccen = pwm->hwpwm < 2 ? TIM_CCER_CC12E : TIM_CCER_CC34E;
+ ccr = pwm->hwpwm < 2 ? TIM_CCR1 : TIM_CCR3;
+ regmap_update_bits(priv->regmap, TIM_CCER, ccen, ccen);
+
+ /*
+ * Timer DMA burst mode. Request 2 registers, 2 bursts, to get both
+ * CCR1 & CCR2 (or CCR3 & CCR4) on each capture event.
+ * We'll get two capture snapchots: { CCR1, CCR2 }, { CCR1, CCR2 }
+ * or { CCR3, CCR4 }, { CCR3, CCR4 }
+ */
+ ret = stm32_timers_dma_burst_read(parent, priv->capture, dma_id, ccr, 2,
+ 2, tmo_ms);
+ if (ret)
+ goto stop;
+
+ /* Period: t2 - t0 (take care of counter overflow) */
+ if (priv->capture[0] <= priv->capture[2])
+ *raw_prd = priv->capture[2] - priv->capture[0];
+ else
+ *raw_prd = priv->max_arr - priv->capture[0] + priv->capture[2];
+
+ /* Duty cycle capture requires at least two capture units */
+ if (pwm->chip->npwm < 2)
+ *raw_dty = 0;
+ else if (priv->capture[0] <= priv->capture[3])
+ *raw_dty = priv->capture[3] - priv->capture[0];
+ else
+ *raw_dty = priv->max_arr - priv->capture[0] + priv->capture[3];
+
+ if (*raw_dty > *raw_prd) {
+ /*
+ * Race beetween PWM input and DMA: it may happen
+ * falling edge triggers new capture on TI2/4 before DMA
+ * had a chance to read CCR2/4. It means capture[1]
+ * contains period + duty_cycle. So, subtract period.
+ */
+ *raw_dty -= *raw_prd;
+ }
+
+stop:
+ regmap_update_bits(priv->regmap, TIM_CCER, ccen, 0);
+ regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0);
+
+ return ret;
+}
+
+static int stm32_pwm_capture(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_capture *result, unsigned long tmo_ms)
+{
+ struct stm32_pwm *priv = to_stm32_pwm_dev(chip);
+ unsigned long long prd, div, dty;
+ unsigned long rate;
+ unsigned int psc = 0, icpsc, scale;
+ u32 raw_prd, raw_dty;
+ int ret = 0;
+
+ mutex_lock(&priv->lock);
+
+ if (active_channels(priv)) {
+ ret = -EBUSY;
+ goto unlock;
+ }
+
+ ret = clk_enable(priv->clk);
+ if (ret) {
+ dev_err(priv->chip.dev, "failed to enable counter clock\n");
+ goto unlock;
+ }
+
+ rate = clk_get_rate(priv->clk);
+ if (!rate) {
+ ret = -EINVAL;
+ goto clk_dis;
+ }
+
+ /* prescaler: fit timeout window provided by upper layer */
+ div = (unsigned long long)rate * (unsigned long long)tmo_ms;
+ do_div(div, MSEC_PER_SEC);
+ prd = div;
+ while ((div > priv->max_arr) && (psc < MAX_TIM_PSC)) {
+ psc++;
+ div = prd;
+ do_div(div, psc + 1);
+ }
+ regmap_write(priv->regmap, TIM_ARR, priv->max_arr);
+ regmap_write(priv->regmap, TIM_PSC, psc);
+
+ /* Map TI1 or TI2 PWM input to IC1 & IC2 (or TI3/4 to IC3 & IC4) */
+ regmap_update_bits(priv->regmap,
+ pwm->hwpwm < 2 ? TIM_CCMR1 : TIM_CCMR2,
+ TIM_CCMR_CC1S | TIM_CCMR_CC2S, pwm->hwpwm & 0x1 ?
+ TIM_CCMR_CC1S_TI2 | TIM_CCMR_CC2S_TI2 :
+ TIM_CCMR_CC1S_TI1 | TIM_CCMR_CC2S_TI1);
+
+ /* Capture period on IC1/3 rising edge, duty cycle on IC2/4 falling. */
+ regmap_update_bits(priv->regmap, TIM_CCER, pwm->hwpwm < 2 ?
+ TIM_CCER_CC12P : TIM_CCER_CC34P, pwm->hwpwm < 2 ?
+ TIM_CCER_CC2P : TIM_CCER_CC4P);
+
+ ret = stm32_pwm_raw_capture(priv, pwm, tmo_ms, &raw_prd, &raw_dty);
+ if (ret)
+ goto stop;
+
+ /*
+ * Got a capture. Try to improve accuracy at high rates:
+ * - decrease counter clock prescaler, scale up to max rate.
+ * - use input prescaler, capture once every /2 /4 or /8 edges.
+ */
+ if (raw_prd) {
+ u32 max_arr = priv->max_arr - 0x1000; /* arbitrary margin */
+
+ scale = max_arr / min(max_arr, raw_prd);
+ } else {
+ scale = priv->max_arr; /* bellow resolution, use max scale */
+ }
+
+ if (psc && scale > 1) {
+ /* 2nd measure with new scale */
+ psc /= scale;
+ regmap_write(priv->regmap, TIM_PSC, psc);
+ ret = stm32_pwm_raw_capture(priv, pwm, tmo_ms, &raw_prd,
+ &raw_dty);
+ if (ret)
+ goto stop;
+ }
+
+ /* Compute intermediate period not to exceed timeout at low rates */
+ prd = (unsigned long long)raw_prd * (psc + 1) * NSEC_PER_SEC;
+ do_div(prd, rate);
+
+ for (icpsc = 0; icpsc < MAX_TIM_ICPSC ; icpsc++) {
+ /* input prescaler: also keep arbitrary margin */
+ if (raw_prd >= (priv->max_arr - 0x1000) >> (icpsc + 1))
+ break;
+ if (prd >= (tmo_ms * NSEC_PER_MSEC) >> (icpsc + 2))
+ break;
+ }
+
+ if (!icpsc)
+ goto done;
+
+ /* Last chance to improve period accuracy, using input prescaler */
+ regmap_update_bits(priv->regmap,
+ pwm->hwpwm < 2 ? TIM_CCMR1 : TIM_CCMR2,
+ TIM_CCMR_IC1PSC | TIM_CCMR_IC2PSC,
+ FIELD_PREP(TIM_CCMR_IC1PSC, icpsc) |
+ FIELD_PREP(TIM_CCMR_IC2PSC, icpsc));
+
+ ret = stm32_pwm_raw_capture(priv, pwm, tmo_ms, &raw_prd, &raw_dty);
+ if (ret)
+ goto stop;
+
+ if (raw_dty >= (raw_prd >> icpsc)) {
+ /*
+ * We may fall here using input prescaler, when input
+ * capture starts on high side (before falling edge).
+ * Example with icpsc to capture on each 4 events:
+ *
+ * start 1st capture 2nd capture
+ * v v v
+ * ___ _____ _____ _____ _____ ____
+ * TI1..4 |__| |__| |__| |__| |__|
+ * v v . . . . . v v
+ * icpsc1/3: . 0 . 1 . 2 . 3 . 0
+ * icpsc2/4: 0 1 2 3 0
+ * v v v v
+ * CCR1/3 ......t0..............................t2
+ * CCR2/4 ..t1..............................t1'...
+ * . . .
+ * Capture0: .<----------------------------->.
+ * Capture1: .<-------------------------->. .
+ * . . .
+ * Period: .<------> . .
+ * Low side: .<>.
+ *
+ * Result:
+ * - Period = Capture0 / icpsc
+ * - Duty = Period - Low side = Period - (Capture0 - Capture1)
+ */
+ raw_dty = (raw_prd >> icpsc) - (raw_prd - raw_dty);
+ }
+
+done:
+ prd = (unsigned long long)raw_prd * (psc + 1) * NSEC_PER_SEC;
+ result->period = DIV_ROUND_UP_ULL(prd, rate << icpsc);
+ dty = (unsigned long long)raw_dty * (psc + 1) * NSEC_PER_SEC;
+ result->duty_cycle = DIV_ROUND_UP_ULL(dty, rate);
+stop:
+ regmap_write(priv->regmap, TIM_CCER, 0);
+ regmap_write(priv->regmap, pwm->hwpwm < 2 ? TIM_CCMR1 : TIM_CCMR2, 0);
+ regmap_write(priv->regmap, TIM_PSC, 0);
+clk_dis:
+ clk_disable(priv->clk);
+unlock:
+ mutex_unlock(&priv->lock);
+
+ return ret;
+}
+
static int stm32_pwm_config(struct stm32_pwm *priv, int ch,
int duty_ns, int period_ns)
{
@@ -230,6 +484,9 @@ static int stm32_pwm_apply_locked(struct pwm_chip *chip, struct pwm_device *pwm,
static const struct pwm_ops stm32pwm_ops = {
.owner = THIS_MODULE,
.apply = stm32_pwm_apply_locked,
+#if IS_ENABLED(CONFIG_DMA_ENGINE)
+ .capture = stm32_pwm_capture,
+#endif
};
static int stm32_pwm_set_breakinput(struct stm32_pwm *priv,
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-15 19:29:00 +0000