[PATCH v4 4/8] clocksource: stm32-lptimer: add support for stm32mp25

[Fabrice Gasnier]

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@xxxxxxxxxxx>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxxxxxxx>
---
Changes in V4:
- Daniel suggests to encapsulate IER write into a separate function
  that manages the enabling/disabling of the LP timer. In addition,
  DIEROK and ARROK flags checks have been added. So adopt a new routine
  to set the event into ARR register and enable the interrupt.
Changes in V2:
- rely on fallback compatible as no specific .data is associated to the
  driver. Use version data from MFD core.
- Added interrupt enable register access update in (missed in V1)
---
 drivers/clocksource/timer-stm32-lp.c | 51 +++++++++++++++++++++++++---
 1 file changed, 47 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/timer-stm32-lp.c b/drivers/clocksource/timer-stm32-lp.c
index 928da2f6de69..e58932300fb4 100644
--- a/drivers/clocksource/timer-stm32-lp.c
+++ b/drivers/clocksource/timer-stm32-lp.c
@@ -27,6 +27,7 @@ struct stm32_lp_private {
 	u32 psc;
 	struct device *dev;
 	struct clk *clk;
+	u32 version;
 };
 
 static struct stm32_lp_private*
@@ -47,12 +48,37 @@ 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;
+
+	/* Enable LPTIMER to be able to write into IER and ARR registers */
+	regmap_write(priv->reg, STM32_LPTIM_CR, STM32_LPTIM_ENABLE);
+	/* 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 +87,22 @@ 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 +218,7 @@ 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)
-- 
2.25.1