[PATCH v5 10/10] counter: stm32-timer-cnt: add support for capture events

From: Fabrice Gasnier
Date: Thu Mar 07 2024 - 08:37:50 EST

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Add support for capture events. Captured counter value for each channel
can be retrieved through CCRx register.
STM32 timers can have up to 4 capture channels (on input channel 1 to
channel 4), hence need to check the number of channels before reading
the capture data.
The capture configuration is hard-coded to capture signals on both edges
(non-inverted). Interrupts are used to report events independently for
each channel.

Reviewed-by: William Breathitt Gray <william.gray@xxxxxxxxxx>
Acked-by: Lee Jones <lee@xxxxxxxxxx>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxxxxxxx>
---
Changes in v5:
- Add William's Reviewed-by tag.

Changes in v4:
- move registers definition from previous patch to here. That's where
the defines are actually used. So move the collected Acked-by: Lee
for the mfd header here.
- drop *irq from stm32_timer_cnt, as only used at probe time.
- adopt some of the suggestions from William: introduce cc local variable,
use regmap_test_bits().

Changes in v3:
- patch split from: "counter: stm32-timer-cnt: add support for events", to
focus on the capture events only here.
- only get relevant interrupt line
---
drivers/counter/stm32-timer-cnt.c | 134 +++++++++++++++++++++++++++++-
include/linux/mfd/stm32-timers.h | 13 +++
2 files changed, 144 insertions(+), 3 deletions(-)

diff --git a/drivers/counter/stm32-timer-cnt.c b/drivers/counter/stm32-timer-cnt.c
index 9fcafec682b7..0664ef969f79 100644
--- a/drivers/counter/stm32-timer-cnt.c
+++ b/drivers/counter/stm32-timer-cnt.c
@@ -262,6 +262,40 @@ static int stm32_count_prescaler_write(struct counter_device *counter,
return regmap_write(priv->regmap, TIM_PSC, psc);
}

+static int stm32_count_cap_read(struct counter_device *counter,
+ struct counter_count *count,
+ size_t ch, u64 *cap)
+{
+ struct stm32_timer_cnt *const priv = counter_priv(counter);
+ u32 ccrx;
+
+ if (ch >= priv->nchannels)
+ return -EOPNOTSUPP;
+
+ switch (ch) {
+ case 0:
+ regmap_read(priv->regmap, TIM_CCR1, &ccrx);
+ break;
+ case 1:
+ regmap_read(priv->regmap, TIM_CCR2, &ccrx);
+ break;
+ case 2:
+ regmap_read(priv->regmap, TIM_CCR3, &ccrx);
+ break;
+ case 3:
+ regmap_read(priv->regmap, TIM_CCR4, &ccrx);
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ dev_dbg(counter->parent, "CCR%zu: 0x%08x\n", ch + 1, ccrx);
+
+ *cap = ccrx;
+
+ return 0;
+}
+
static int stm32_count_nb_ovf_read(struct counter_device *counter,
struct counter_count *count, u64 *val)
{
@@ -288,6 +322,8 @@ static int stm32_count_nb_ovf_write(struct counter_device *counter,
return 0;
}

+static DEFINE_COUNTER_ARRAY_CAPTURE(stm32_count_cap_array, 4);
+
static struct counter_comp stm32_count_ext[] = {
COUNTER_COMP_DIRECTION(stm32_count_direction_read),
COUNTER_COMP_ENABLE(stm32_count_enable_read, stm32_count_enable_write),
@@ -295,6 +331,7 @@ static struct counter_comp stm32_count_ext[] = {
stm32_count_ceiling_write),
COUNTER_COMP_COUNT_U64("prescaler", stm32_count_prescaler_read,
stm32_count_prescaler_write),
+ COUNTER_COMP_ARRAY_CAPTURE(stm32_count_cap_read, NULL, stm32_count_cap_array),
COUNTER_COMP_COUNT_U64("num_overflows", stm32_count_nb_ovf_read, stm32_count_nb_ovf_write),
};

@@ -353,11 +390,68 @@ static int stm32_action_read(struct counter_device *counter,
}
}

+struct stm32_count_cc_regs {
+ u32 ccmr_reg;
+ u32 ccmr_mask;
+ u32 ccmr_bits;
+ u32 ccer_bits;
+};
+
+static const struct stm32_count_cc_regs stm32_cc[] = {
+ { TIM_CCMR1, TIM_CCMR_CC1S, TIM_CCMR_CC1S_TI1,
+ TIM_CCER_CC1E | TIM_CCER_CC1P | TIM_CCER_CC1NP },
+ { TIM_CCMR1, TIM_CCMR_CC2S, TIM_CCMR_CC2S_TI2,
+ TIM_CCER_CC2E | TIM_CCER_CC2P | TIM_CCER_CC2NP },
+ { TIM_CCMR2, TIM_CCMR_CC3S, TIM_CCMR_CC3S_TI3,
+ TIM_CCER_CC3E | TIM_CCER_CC3P | TIM_CCER_CC3NP },
+ { TIM_CCMR2, TIM_CCMR_CC4S, TIM_CCMR_CC4S_TI4,
+ TIM_CCER_CC4E | TIM_CCER_CC4P | TIM_CCER_CC4NP },
+};
+
+static int stm32_count_capture_configure(struct counter_device *counter, unsigned int ch,
+ bool enable)
+{
+ struct stm32_timer_cnt *const priv = counter_priv(counter);
+ const struct stm32_count_cc_regs *cc;
+ u32 ccmr, ccer;
+
+ if (ch >= ARRAY_SIZE(stm32_cc) || ch >= priv->nchannels) {
+ dev_err(counter->parent, "invalid ch: %d\n", ch);
+ return -EINVAL;
+ }
+
+ cc = &stm32_cc[ch];
+
+ /*
+ * configure channel in input capture mode, map channel 1 on TI1, channel2 on TI2...
+ * Select both edges / non-inverted to trigger a capture.
+ */
+ if (enable) {
+ /* first clear possibly latched capture flag upon enabling */
+ if (!regmap_test_bits(priv->regmap, TIM_CCER, cc->ccer_bits))
+ regmap_write(priv->regmap, TIM_SR, ~TIM_SR_CC_IF(ch));
+ regmap_update_bits(priv->regmap, cc->ccmr_reg, cc->ccmr_mask,
+ cc->ccmr_bits);
+ regmap_set_bits(priv->regmap, TIM_CCER, cc->ccer_bits);
+ } else {
+ regmap_clear_bits(priv->regmap, TIM_CCER, cc->ccer_bits);
+ regmap_clear_bits(priv->regmap, cc->ccmr_reg, cc->ccmr_mask);
+ }
+
+ regmap_read(priv->regmap, cc->ccmr_reg, &ccmr);
+ regmap_read(priv->regmap, TIM_CCER, &ccer);
+ dev_dbg(counter->parent, "%s(%s) ch%d 0x%08x 0x%08x\n", __func__, enable ? "ena" : "dis",
+ ch, ccmr, ccer);
+
+ return 0;
+}
+
static int stm32_count_events_configure(struct counter_device *counter)
{
struct stm32_timer_cnt *const priv = counter_priv(counter);
struct counter_event_node *event_node;
u32 dier = 0;
+ int i, ret;

list_for_each_entry(event_node, &counter->events_list, l) {
switch (event_node->event) {
@@ -367,6 +461,12 @@ static int stm32_count_events_configure(struct counter_device *counter)
regmap_write(priv->regmap, TIM_SR, (u32)~TIM_SR_UIF);
dier |= TIM_DIER_UIE;
break;
+ case COUNTER_EVENT_CAPTURE:
+ ret = stm32_count_capture_configure(counter, event_node->channel, true);
+ if (ret)
+ return ret;
+ dier |= TIM_DIER_CC_IE(event_node->channel);
+ break;
default:
/* should never reach this path */
return -EINVAL;
@@ -376,6 +476,15 @@ static int stm32_count_events_configure(struct counter_device *counter)
/* Enable / disable all events at once, from events_list, so write all DIER bits */
regmap_write(priv->regmap, TIM_DIER, dier);

+ /* check for disabled capture events */
+ for (i = 0 ; i < priv->nchannels; i++) {
+ if (!(dier & TIM_DIER_CC_IE(i))) {
+ ret = stm32_count_capture_configure(counter, i, false);
+ if (ret)
+ return ret;
+ }
+ }
+
return 0;
}

@@ -389,6 +498,12 @@ static int stm32_count_watch_validate(struct counter_device *counter,
return -EOPNOTSUPP;

switch (watch->event) {
+ case COUNTER_EVENT_CAPTURE:
+ if (watch->channel >= priv->nchannels) {
+ dev_err(counter->parent, "Invalid channel %d\n", watch->channel);
+ return -EINVAL;
+ }
+ return 0;
case COUNTER_EVENT_OVERFLOW_UNDERFLOW:
return 0;
default:
@@ -499,6 +614,7 @@ static irqreturn_t stm32_timer_cnt_isr(int irq, void *ptr)
struct stm32_timer_cnt *const priv = counter_priv(counter);
u32 clr = GENMASK(31, 0); /* SR flags can be cleared by writing 0 (wr 1 has no effect) */
u32 sr, dier;
+ int i;

regmap_read(priv->regmap, TIM_SR, &sr);
regmap_read(priv->regmap, TIM_DIER, &dier);
@@ -506,7 +622,7 @@ static irqreturn_t stm32_timer_cnt_isr(int irq, void *ptr)
* Some status bits in SR don't match with the enable bits in DIER. Only take care of
* the possibly enabled bits in DIER (that matches in between SR and DIER).
*/
- dier &= TIM_DIER_UIE;
+ dier &= (TIM_DIER_UIE | TIM_DIER_CC1IE | TIM_DIER_CC2IE | TIM_DIER_CC3IE | TIM_DIER_CC4IE);
sr &= dier;

if (sr & TIM_SR_UIF) {
@@ -519,6 +635,15 @@ static irqreturn_t stm32_timer_cnt_isr(int irq, void *ptr)
clr &= ~TIM_SR_UIF;
}

+ /* Check capture events */
+ for (i = 0 ; i < priv->nchannels; i++) {
+ if (sr & TIM_SR_CC_IF(i)) {
+ counter_push_event(counter, COUNTER_EVENT_CAPTURE, i);
+ clr &= ~TIM_SR_CC_IF(i);
+ dev_dbg(counter->parent, "COUNTER_EVENT_CAPTURE, %d\n", i);
+ }
+ }
+
regmap_write(priv->regmap, TIM_SR, clr);

return IRQ_HANDLED;
@@ -633,8 +758,11 @@ static int stm32_timer_cnt_probe(struct platform_device *pdev)
}
} else {
for (i = 0; i < priv->nr_irqs; i++) {
- /* Only take care of update IRQ for overflow events */
- if (i != STM32_TIMERS_IRQ_UP)
+ /*
+ * Only take care of update IRQ for overflow events, and cc for
+ * capture events.
+ */
+ if (i != STM32_TIMERS_IRQ_UP && i != STM32_TIMERS_IRQ_CC)
continue;

ret = devm_request_irq(&pdev->dev, ddata->irq[i], stm32_timer_cnt_isr,
diff --git a/include/linux/mfd/stm32-timers.h b/include/linux/mfd/stm32-timers.h
index ca35af30745f..9eb17481b07f 100644
--- a/include/linux/mfd/stm32-timers.h
+++ b/include/linux/mfd/stm32-timers.h
@@ -41,6 +41,11 @@
#define TIM_SMCR_SMS (BIT(0) | BIT(1) | BIT(2)) /* Slave mode selection */
#define TIM_SMCR_TS (BIT(4) | BIT(5) | BIT(6)) /* Trigger selection */
#define TIM_DIER_UIE BIT(0) /* Update interrupt */
+#define TIM_DIER_CC1IE BIT(1) /* CC1 Interrupt Enable */
+#define TIM_DIER_CC2IE BIT(2) /* CC2 Interrupt Enable */
+#define TIM_DIER_CC3IE BIT(3) /* CC3 Interrupt Enable */
+#define TIM_DIER_CC4IE BIT(4) /* CC4 Interrupt Enable */
+#define TIM_DIER_CC_IE(x) BIT((x) + 1) /* CC1, CC2, CC3, CC4 interrupt enable */
#define TIM_DIER_UDE BIT(8) /* Update DMA request Enable */
#define TIM_DIER_CC1DE BIT(9) /* CC1 DMA request Enable */
#define TIM_DIER_CC2DE BIT(10) /* CC2 DMA request Enable */
@@ -49,6 +54,7 @@
#define TIM_DIER_COMDE BIT(13) /* COM DMA request Enable */
#define TIM_DIER_TDE BIT(14) /* Trigger DMA request Enable */
#define TIM_SR_UIF BIT(0) /* Update interrupt flag */
+#define TIM_SR_CC_IF(x) BIT((x) + 1) /* CC1, CC2, CC3, CC4 interrupt flag */
#define TIM_EGR_UG BIT(0) /* Update Generation */
#define TIM_CCMR_PE BIT(3) /* Channel Preload Enable */
#define TIM_CCMR_M1 (BIT(6) | BIT(5)) /* Channel PWM Mode 1 */
@@ -60,16 +66,23 @@
#define TIM_CCMR_CC1S_TI2 BIT(1) /* IC1/IC3 selects TI2/TI4 */
#define TIM_CCMR_CC2S_TI2 BIT(8) /* IC2/IC4 selects TI2/TI4 */
#define TIM_CCMR_CC2S_TI1 BIT(9) /* IC2/IC4 selects TI1/TI3 */
+#define TIM_CCMR_CC3S (BIT(0) | BIT(1)) /* Capture/compare 3 sel */
+#define TIM_CCMR_CC4S (BIT(8) | BIT(9)) /* Capture/compare 4 sel */
+#define TIM_CCMR_CC3S_TI3 BIT(0) /* IC3 selects TI3 */
+#define TIM_CCMR_CC4S_TI4 BIT(8) /* IC4 selects TI4 */
#define TIM_CCER_CC1E BIT(0) /* Capt/Comp 1 out Ena */
#define TIM_CCER_CC1P BIT(1) /* Capt/Comp 1 Polarity */
#define TIM_CCER_CC1NE BIT(2) /* Capt/Comp 1N out Ena */
#define TIM_CCER_CC1NP BIT(3) /* Capt/Comp 1N Polarity */
#define TIM_CCER_CC2E BIT(4) /* Capt/Comp 2 out Ena */
#define TIM_CCER_CC2P BIT(5) /* Capt/Comp 2 Polarity */
+#define TIM_CCER_CC2NP BIT(7) /* Capt/Comp 2N Polarity */
#define TIM_CCER_CC3E BIT(8) /* Capt/Comp 3 out Ena */
#define TIM_CCER_CC3P BIT(9) /* Capt/Comp 3 Polarity */
+#define TIM_CCER_CC3NP BIT(11) /* Capt/Comp 3N Polarity */
#define TIM_CCER_CC4E BIT(12) /* Capt/Comp 4 out Ena */
#define TIM_CCER_CC4P BIT(13) /* Capt/Comp 4 Polarity */
+#define TIM_CCER_CC4NP BIT(15) /* Capt/Comp 4N Polarity */
#define TIM_CCER_CCXE (BIT(0) | BIT(4) | BIT(8) | BIT(12))
#define TIM_BDTR_BKE(x) BIT(12 + (x) * 12) /* Break input enable */
#define TIM_BDTR_BKP(x) BIT(13 + (x) * 12) /* Break input polarity */
--
2.25.1

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