linux-kernel - [PATCH v4 09/11] counter: stm32-timer-cnt: probe number of channels from registers

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Message-ID: <20240227173803.53906-10-fabrice.gasnier@foss.st.com>
Date: Tue, 27 Feb 2024 18:38:01 +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 v4 09/11] counter: stm32-timer-cnt: probe number of channels from registers

Probe the number of capture compare channels, by writing CCER register bits
and read them back. Take care to restore the register original value.

This is a precursor patch to support capture channels.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
---
Changes in v4:
- directly use dev struct in stm32_timer_cnt_detect_channels routine.
Changes in v3:
- New patch split from:
  "counter: stm32-timer-cnt: populate capture channels and check encoder"
---
 drivers/counter/stm32-timer-cnt.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/counter/stm32-timer-cnt.c b/drivers/counter/stm32-timer-cnt.c
index 66039d1b3642..710437d3b33f 100644
--- a/drivers/counter/stm32-timer-cnt.c
+++ b/drivers/counter/stm32-timer-cnt.c
@@ -42,6 +42,7 @@ struct stm32_timer_cnt {
 	bool enabled;
 	struct stm32_timer_regs bak;
 	bool has_encoder;
+	unsigned int nchannels;
 };
 
 static const enum counter_function stm32_count_functions[] = {
@@ -416,6 +417,20 @@ static struct counter_count stm32_counts = {
 	.num_ext = ARRAY_SIZE(stm32_count_ext)
 };
 
+static void stm32_timer_cnt_detect_channels(struct device *dev,
+					    struct stm32_timer_cnt *priv)
+{
+	u32 ccer, ccer_backup;
+
+	regmap_read(priv->regmap, TIM_CCER, &ccer_backup);
+	regmap_set_bits(priv->regmap, TIM_CCER, TIM_CCER_CCXE);
+	regmap_read(priv->regmap, TIM_CCER, &ccer);
+	regmap_write(priv->regmap, TIM_CCER, ccer_backup);
+	priv->nchannels = hweight32(ccer & TIM_CCER_CCXE);
+
+	dev_dbg(dev, "has %d cc channels\n", priv->nchannels);
+}
+
 /* encoder supported on TIM1 TIM2 TIM3 TIM4 TIM5 TIM8 */
 #define STM32_TIM_ENCODER_SUPPORTED	(BIT(0) | BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(7))
 
@@ -484,6 +499,8 @@ static int stm32_timer_cnt_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	stm32_timer_cnt_detect_channels(dev, priv);
+
 	counter->name = dev_name(dev);
 	counter->parent = dev;
 	counter->ops = &stm32_timer_cnt_ops;
-- 
2.25.1