can: flexcan: add low power enter/exit acknowledgment helper

The MCR[LPMACK] read-only bit indicates that FlexCAN is in a lower-power
mode (Disabled mode, Doze mode, Stop mode).

The CPU can poll this bit to know when FlexCAN has actually entered low
power mode. The low power enter/exit acknowledgment helper will reduce
code duplication for disabled mode, doze mode and stop mode.
Tested-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/flexcan.c

@@ -389,6 +389,34 @@ static struct flexcan_mb __iomem *flexcan_get_mb(const struct flexcan_priv *priv
 		(&priv->regs->mb[bank][priv->mb_size * mb_index]);
 }
 
+static int flexcan_low_power_enter_ack(struct flexcan_priv *priv)
+{
+	struct flexcan_regs __iomem *regs = priv->regs;
+	unsigned int timeout = FLEXCAN_TIMEOUT_US / 10;
+
+	while (timeout-- && !(priv->read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK))
+		udelay(10);
+
+	if (!(priv->read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK))
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+static int flexcan_low_power_exit_ack(struct flexcan_priv *priv)
+{
+	struct flexcan_regs __iomem *regs = priv->regs;
+	unsigned int timeout = FLEXCAN_TIMEOUT_US / 10;
+
+	while (timeout-- && (priv->read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK))
+		udelay(10);
+
+	if (priv->read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
 static void flexcan_enable_wakeup_irq(struct flexcan_priv *priv, bool enable)
 {
 	struct flexcan_regs __iomem *regs = priv->regs;
@@ -506,39 +534,25 @@ static inline int flexcan_transceiver_disable(const struct flexcan_priv *priv)
 static int flexcan_chip_enable(struct flexcan_priv *priv)
 {
 	struct flexcan_regs __iomem *regs = priv->regs;
-	unsigned int timeout = FLEXCAN_TIMEOUT_US / 10;
 	u32 reg;
 
 	reg = priv->read(&regs->mcr);
 	reg &= ~FLEXCAN_MCR_MDIS;
 	priv->write(reg, &regs->mcr);
 
-	while (timeout-- && (priv->read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK))
-		udelay(10);
-
-	if (priv->read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK)
-		return -ETIMEDOUT;
-
-	return 0;
+	return flexcan_low_power_exit_ack(priv);
 }
 
 static int flexcan_chip_disable(struct flexcan_priv *priv)
 {
 	struct flexcan_regs __iomem *regs = priv->regs;
-	unsigned int timeout = FLEXCAN_TIMEOUT_US / 10;
 	u32 reg;
 
 	reg = priv->read(&regs->mcr);
 	reg |= FLEXCAN_MCR_MDIS;
 	priv->write(reg, &regs->mcr);
 
-	while (timeout-- && !(priv->read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK))
-		udelay(10);
-
-	if (!(priv->read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK))
-		return -ETIMEDOUT;
-
-	return 0;
+	return flexcan_low_power_enter_ack(priv);
 }
 
 static int flexcan_chip_freeze(struct flexcan_priv *priv)