[PATCH v2 4/8] clocksource: stm32-lptimer: add support for stm32mp25

[Fabrice Gasnier <fabrice.gasnier@xxxxxxxxxxx>]

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. Read the LPTIM_VERR register to properly manage the enable
state, before accessing IER.

Signed-off-by: Patrick Delaunay <patrick.delaunay@xxxxxxxxxxx>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxxxxxxx>
---
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 | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/timer-stm32-lp.c b/drivers/clocksource/timer-stm32-lp.c
index a4c95161cb22..96d975adf7a4 100644
--- a/drivers/clocksource/timer-stm32-lp.c
+++ b/drivers/clocksource/timer-stm32-lp.c
@@ -25,6 +25,7 @@ struct stm32_lp_private {
 	struct clock_event_device clkevt;
 	unsigned long period;
 	struct device *dev;
+	bool ier_wr_enabled;	/* Enables LPTIMER before writing into IER register */
 };
 
 static struct stm32_lp_private*
@@ -37,8 +38,15 @@ static int stm32_clkevent_lp_shutdown(struct clock_event_device *clkevt)
 {
 	struct stm32_lp_private *priv = to_priv(clkevt);
 
-	regmap_write(priv->reg, STM32_LPTIM_CR, 0);
+	/* Disable LPTIMER either before or after writing IER register (else, keep it enabled) */
+	if (!priv->ier_wr_enabled)
+		regmap_write(priv->reg, STM32_LPTIM_CR, 0);
+
 	regmap_write(priv->reg, STM32_LPTIM_IER, 0);
+
+	if (priv->ier_wr_enabled)
+		regmap_write(priv->reg, STM32_LPTIM_CR, 0);
+
 	/* clear pending flags */
 	regmap_write(priv->reg, STM32_LPTIM_ICR, STM32_LPTIM_ARRMCF);
 
@@ -51,12 +59,21 @@ static int stm32_clkevent_lp_set_timer(unsigned long evt,
 {
 	struct stm32_lp_private *priv = to_priv(clkevt);
 
-	/* disable LPTIMER to be able to write into IER register*/
-	regmap_write(priv->reg, STM32_LPTIM_CR, 0);
+	if (!priv->ier_wr_enabled) {
+		/* Disable LPTIMER to be able to write into IER register */
+		regmap_write(priv->reg, STM32_LPTIM_CR, 0);
+	} else {
+		/* Enable LPTIMER to be able to write into IER register */
+		regmap_write(priv->reg, STM32_LPTIM_CR, STM32_LPTIM_ENABLE);
+	}
+
 	/* enable ARR interrupt */
 	regmap_write(priv->reg, STM32_LPTIM_IER, STM32_LPTIM_ARRMIE);
+
 	/* enable LPTIMER to be able to write into ARR register */
-	regmap_write(priv->reg, STM32_LPTIM_CR, STM32_LPTIM_ENABLE);
+	if (!priv->ier_wr_enabled)
+		regmap_write(priv->reg, STM32_LPTIM_CR, STM32_LPTIM_ENABLE);
+
 	/* set next event counter */
 	regmap_write(priv->reg, STM32_LPTIM_ARR, evt);
 
@@ -151,6 +168,7 @@ static int stm32_clkevent_lp_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	priv->reg = ddata->regmap;
+	priv->ier_wr_enabled = ddata->version == STM32_LPTIM_VERR_23;
 	ret = clk_prepare_enable(ddata->clk);
 	if (ret)
 		return -EINVAL;
-- 
2.25.1