clocksource/drivers/stm32-lptimer: Add support for stm32mp25

On stm32mp25, DIER (former IER) must only be modified when the lptimer
is enabled. On earlier SoCs, it must be only be modified when it is
disabled. There's also a new DIEROK flag, to ensure register access
has completed.
Add a new "set_evt" routine to be used on stm32mp25, called depending
on the version register, read by the MFD core (LPTIM_VERR).

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20250429125133.1574167-4-fabrice.gasnier@foss.st.com
Signed-off-by: Lee Jones <lee@kernel.org>

1 files changed, 57 insertions, 4 deletions

diff --git a/drivers/clocksource/timer-stm32-lp.c b/drivers/clocksource/timer-stm32-lp.c
index 928da2f6de69e..6e7944ffd7c03 100644
--- a/drivers/clocksource/timer-stm32-lp.c
+++ b/drivers/clocksource/timer-stm32-lp.c
@@ -5,6 +5,7 @@
  *	    Pascal Paillet <p.paillet@st.com> for STMicroelectronics.
  */
 
+#include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/clockchips.h>
 #include <linux/interrupt.h>
@@ -27,6 +28,7 @@ struct stm32_lp_private {
 	u32 psc;
 	struct device *dev;
 	struct clk *clk;
+	u32 version;
 };
 
 static struct stm32_lp_private*
@@ -47,12 +49,46 @@ static int stm32_clkevent_lp_shutdown(struct clock_event_device *clkevt)
 	return 0;
 }
 
-static int stm32_clkevent_lp_set_timer(unsigned long evt,
-				       struct clock_event_device *clkevt,
-				       int is_periodic)
+static int stm32mp25_clkevent_lp_set_evt(struct stm32_lp_private *priv, unsigned long evt)
 {
-	struct stm32_lp_private *priv = to_priv(clkevt);
+	int ret;
+	u32 val;
+
+	regmap_read(priv->reg, STM32_LPTIM_CR, &val);
+	if (!FIELD_GET(STM32_LPTIM_ENABLE, val)) {
+		/* Enable LPTIMER to be able to write into IER and ARR registers */
+		regmap_write(priv->reg, STM32_LPTIM_CR, STM32_LPTIM_ENABLE);
+		/*
+		 * After setting the ENABLE bit, a delay of two counter clock cycles is needed
+		 * before the LPTIM is actually enabled. For 32KHz rate, this makes approximately
+		 * 62.5 micro-seconds, round it up.
+		 */
+		udelay(63);
+	}
+	/* set next event counter */
+	regmap_write(priv->reg, STM32_LPTIM_ARR, evt);
+	/* enable ARR interrupt */
+	regmap_write(priv->reg, STM32_LPTIM_IER, STM32_LPTIM_ARRMIE);
+
+	/* Poll DIEROK and ARROK to ensure register access has completed */
+	ret = regmap_read_poll_timeout_atomic(priv->reg, STM32_LPTIM_ISR, val,
+					      (val & STM32_LPTIM_DIEROK_ARROK) ==
+					      STM32_LPTIM_DIEROK_ARROK,
+					      10, 500);
+	if (ret) {
+		dev_err(priv->dev, "access to LPTIM timed out\n");
+		/* Disable LPTIMER */
+		regmap_write(priv->reg, STM32_LPTIM_CR, 0);
+		return ret;
+	}
+	/* Clear DIEROK and ARROK flags */
+	regmap_write(priv->reg, STM32_LPTIM_ICR, STM32_LPTIM_DIEROKCF_ARROKCF);
 
+	return 0;
+}
+
+static void stm32_clkevent_lp_set_evt(struct stm32_lp_private *priv, unsigned long evt)
+{
 	/* disable LPTIMER to be able to write into IER register*/
 	regmap_write(priv->reg, STM32_LPTIM_CR, 0);
 	/* enable ARR interrupt */
@@ -61,6 +97,22 @@ static int stm32_clkevent_lp_set_timer(unsigned long evt,
 	regmap_write(priv->reg, STM32_LPTIM_CR, STM32_LPTIM_ENABLE);
 	/* set next event counter */
 	regmap_write(priv->reg, STM32_LPTIM_ARR, evt);
+}
+
+static int stm32_clkevent_lp_set_timer(unsigned long evt,
+				       struct clock_event_device *clkevt,
+				       int is_periodic)
+{
+	struct stm32_lp_private *priv = to_priv(clkevt);
+	int ret;
+
+	if (priv->version == STM32_LPTIM_VERR_23) {
+		ret = stm32mp25_clkevent_lp_set_evt(priv, evt);
+		if (ret)
+			return ret;
+	} else {
+		stm32_clkevent_lp_set_evt(priv, evt);
+	}
 
 	/* start counter */
 	if (is_periodic)
@@ -176,6 +228,7 @@ static int stm32_clkevent_lp_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	priv->reg = ddata->regmap;
+	priv->version = ddata->version;
 	priv->clk = ddata->clk;
 	ret = clk_prepare_enable(priv->clk);
 	if (ret)