[PATCH] can: flexcan: fix stop mode acknowledgment

[Joakim Zhang <qiangqing.zhang@xxxxxxx>]

To enter stop mode, the CPU should manually assert a global Stop Mode
request and check the acknowledgment asserted by FlexCAN. The CPU must
only consider the FlexCAN in stop mode when both request and
acknowledgment conditions are satisfied.

Fixes: de3578c198c6 ("can: flexcan: add self wakeup support")
Reported-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Joakim Zhang <qiangqing.zhang@xxxxxxx>
---
 drivers/net/can/flexcan.c | 47 ++++++++++++++++++++++++++++++++-------
 1 file changed, 39 insertions(+), 8 deletions(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index e35083ff31ee..282dac1d8f5c 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -404,9 +404,11 @@ static void flexcan_enable_wakeup_irq(struct flexcan_priv *priv, bool enable)
 	priv->write(reg_mcr, &regs->mcr);
 }
 
-static inline void flexcan_enter_stop_mode(struct flexcan_priv *priv)
+static inline int flexcan_enter_stop_mode(struct flexcan_priv *priv)
 {
 	struct flexcan_regs __iomem *regs = priv->regs;
+	unsigned int timeout = FLEXCAN_TIMEOUT_US / 10;
+	unsigned int ackval;
 	u32 reg_mcr;
 
 	reg_mcr = priv->read(&regs->mcr);
@@ -416,20 +418,48 @@ static inline void flexcan_enter_stop_mode(struct flexcan_priv *priv)
 	/* enable stop request */
 	regmap_update_bits(priv->stm.gpr, priv->stm.req_gpr,
 			   1 << priv->stm.req_bit, 1 << priv->stm.req_bit);
+
+	/* get stop acknowledgment */
+	regmap_read(priv->stm.gpr, priv->stm.ack_gpr, &ackval);
+
+	while (timeout-- && !(ackval & (1 << priv->stm.ack_bit))) {
+		udelay(10);
+		regmap_read(priv->stm.gpr, priv->stm.ack_gpr, &ackval);
+	}
+
+	if (!(ackval & (1 << priv->stm.ack_bit)))
+		return -ETIMEDOUT;
+
+	return 0;
 }
 
-static inline void flexcan_exit_stop_mode(struct flexcan_priv *priv)
+static inline int flexcan_exit_stop_mode(struct flexcan_priv *priv)
 {
 	struct flexcan_regs __iomem *regs = priv->regs;
+	unsigned int timeout = FLEXCAN_TIMEOUT_US / 10;
+	unsigned int ackval;
 	u32 reg_mcr;
 
+	reg_mcr = priv->read(&regs->mcr);
+	reg_mcr &= ~FLEXCAN_MCR_SLF_WAK;
+	priv->write(reg_mcr, &regs->mcr);
+
 	/* remove stop request */
 	regmap_update_bits(priv->stm.gpr, priv->stm.req_gpr,
 			   1 << priv->stm.req_bit, 0);
 
-	reg_mcr = priv->read(&regs->mcr);
-	reg_mcr &= ~FLEXCAN_MCR_SLF_WAK;
-	priv->write(reg_mcr, &regs->mcr);
+	/* get stop acknowledgment */
+	regmap_read(priv->stm.gpr, priv->stm.ack_gpr, &ackval);
+
+	while (timeout-- && (ackval & (1 << priv->stm.ack_bit))) {
+		udelay(10);
+		regmap_read(priv->stm.gpr, priv->stm.ack_gpr, &ackval);
+	}
+
+	if (ackval & (1 << priv->stm.ack_bit))
+		return -ETIMEDOUT;
+
+	return 0;
 }
 
 static inline void flexcan_error_irq_enable(const struct flexcan_priv *priv)
@@ -1652,7 +1682,7 @@ static int __maybe_unused flexcan_suspend(struct device *device)
 		 */
 		if (device_may_wakeup(device)) {
 			enable_irq_wake(dev->irq);
-			flexcan_enter_stop_mode(priv);
+			err = flexcan_enter_stop_mode(priv);
 		} else {
 			err = flexcan_chip_disable(priv);
 			if (err)
@@ -1725,13 +1755,14 @@ static int __maybe_unused flexcan_noirq_resume(struct device *device)
 {
 	struct net_device *dev = dev_get_drvdata(device);
 	struct flexcan_priv *priv = netdev_priv(dev);
+	int err = 0;
 
 	if (netif_running(dev) && device_may_wakeup(device)) {
 		flexcan_enable_wakeup_irq(priv, false);
-		flexcan_exit_stop_mode(priv);
+		err = flexcan_exit_stop_mode(priv);
 	}
 
-	return 0;
+	return err;
 }
 
 static const struct dev_pm_ops flexcan_pm_ops = {
-- 
2.17.1