linux-kernel - [PATCH v5 04/10] counter: stm32-timer-cnt: introduce clock signal

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Date: Thu, 7 Mar 2024 14:33:00 +0100
From: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
To: <william.gray@...aro.org>
CC: <lee@...nel.org>, <alexandre.torgue@...s.st.com>,
        <fabrice.gasnier@...s.st.com>, <linux-iio@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v5 04/10] counter: stm32-timer-cnt: introduce clock signal

Introduce the internal clock signal, used to count when in simple rising
function. Also add the "frequency" extension to the clock signal.

With this patch, signal action reports a consistent state when "increase"
function is used, and the counting frequency:
    $ echo increase > function
    $ grep -H "" signal*_action
    signal0_action:none
    signal1_action:none
    signal2_action:rising edge
    $ echo 1 > enable
    $ cat count
    25425
    $ cat count
    44439
    $ cat ../signal2/frequency
    208877930

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
---
Changes in v5:
- removed NULL write parameter in COUNTER_COMP_FREQUENCY() macro.

Changes in v4:
- Introduce COUNTER_COMP_FREQUENCY() macro as suggested by William in [1]
[1] https://lore.kernel.org/lkml/ZZwm7ZyrL7vFn0Xd@ubuntu-server-vm-macos/
- Remove "Signal" from "Clock Signal" name which is redundant with sysfs
  path that already has signal as a name.

Changes in v3:
- split the patch in 3 parts: signal definition becomes a pre-cursor patch,
  add the "prescaler" extension in its own patch.
- Move the clock signal at the end of the signals array, so existing
  userspace programs that may rely on signal0 being "Channel 1" for
  example will remain compatible.
---
 drivers/counter/stm32-timer-cnt.c | 53 ++++++++++++++++++++++++++++---
 1 file changed, 49 insertions(+), 4 deletions(-)

diff --git a/drivers/counter/stm32-timer-cnt.c b/drivers/counter/stm32-timer-cnt.c
index c34747d7857e..65b447b42e75 100644
--- a/drivers/counter/stm32-timer-cnt.c
+++ b/drivers/counter/stm32-timer-cnt.c
@@ -23,6 +23,7 @@
 
 #define STM32_CH1_SIG		0
 #define STM32_CH2_SIG		1
+#define STM32_CLOCK_SIG		2
 
 struct stm32_timer_regs {
 	u32 cr1;
@@ -226,6 +227,10 @@ static struct counter_comp stm32_count_ext[] = {
 			     stm32_count_ceiling_write),
 };
 
+static const enum counter_synapse_action stm32_clock_synapse_actions[] = {
+	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
+};
+
 static const enum counter_synapse_action stm32_synapse_actions[] = {
 	COUNTER_SYNAPSE_ACTION_NONE,
 	COUNTER_SYNAPSE_ACTION_BOTH_EDGES
@@ -246,7 +251,10 @@ static int stm32_action_read(struct counter_device *counter,
 	switch (function) {
 	case COUNTER_FUNCTION_INCREASE:
 		/* counts on internal clock when CEN=1 */
-		*action = COUNTER_SYNAPSE_ACTION_NONE;
+		if (synapse->signal->id == STM32_CLOCK_SIG)
+			*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
+		else
+			*action = COUNTER_SYNAPSE_ACTION_NONE;
 		return 0;
 	case COUNTER_FUNCTION_QUADRATURE_X2_A:
 		/* counts up/down on TI1FP1 edge depending on TI2FP2 level */
@@ -264,7 +272,10 @@ static int stm32_action_read(struct counter_device *counter,
 		return 0;
 	case COUNTER_FUNCTION_QUADRATURE_X4:
 		/* counts up/down on both TI1FP1 and TI2FP2 edges */
-		*action = COUNTER_SYNAPSE_ACTION_BOTH_EDGES;
+		if (synapse->signal->id == STM32_CH1_SIG || synapse->signal->id == STM32_CH2_SIG)
+			*action = COUNTER_SYNAPSE_ACTION_BOTH_EDGES;
+		else
+			*action = COUNTER_SYNAPSE_ACTION_NONE;
 		return 0;
 	default:
 		return -EINVAL;
@@ -279,7 +290,30 @@ static const struct counter_ops stm32_timer_cnt_ops = {
 	.action_read = stm32_action_read,
 };
 
+static int stm32_count_clk_get_freq(struct counter_device *counter,
+				    struct counter_signal *signal, u64 *freq)
+{
+	struct stm32_timer_cnt *const priv = counter_priv(counter);
+
+	*freq = clk_get_rate(priv->clk);
+
+	return 0;
+}
+
+static struct counter_comp stm32_count_clock_ext[] = {
+	COUNTER_COMP_FREQUENCY(stm32_count_clk_get_freq),
+};
+
 static struct counter_signal stm32_signals[] = {
+	/*
+	 * Need to declare all the signals as a static array, and keep the signals order here,
+	 * even if they're unused or unexisting on some timer instances. It's an abstraction,
+	 * e.g. high level view of the counter features.
+	 *
+	 * Userspace programs may rely on signal0 to be "Channel 1", signal1 to be "Channel 2",
+	 * and so on. When a signal is unexisting, the COUNTER_SYNAPSE_ACTION_NONE can be used,
+	 * to indicate that a signal doesn't affect the counter.
+	 */
 	{
 		.id = STM32_CH1_SIG,
 		.name = "Channel 1"
@@ -287,7 +321,13 @@ static struct counter_signal stm32_signals[] = {
 	{
 		.id = STM32_CH2_SIG,
 		.name = "Channel 2"
-	}
+	},
+	{
+		.id = STM32_CLOCK_SIG,
+		.name = "Clock",
+		.ext = stm32_count_clock_ext,
+		.num_ext = ARRAY_SIZE(stm32_count_clock_ext),
+	},
 };
 
 static struct counter_synapse stm32_count_synapses[] = {
@@ -300,7 +340,12 @@ static struct counter_synapse stm32_count_synapses[] = {
 		.actions_list = stm32_synapse_actions,
 		.num_actions = ARRAY_SIZE(stm32_synapse_actions),
 		.signal = &stm32_signals[STM32_CH2_SIG]
-	}
+	},
+	{
+		.actions_list = stm32_clock_synapse_actions,
+		.num_actions = ARRAY_SIZE(stm32_clock_synapse_actions),
+		.signal = &stm32_signals[STM32_CLOCK_SIG]
+	},
 };
 
 static struct counter_count stm32_counts = {
-- 
2.25.1