[PATCH linux-can] can: flexcan: enable RX FIFO after FRZ/HALT valid

[Joakim Zhang <qiangqing.zhang@xxxxxxx>]

RX FIFO enable failed could happen when do system reboot stress test,
one customer reports failure rate is about 50%.

[    0.303958] flexcan 5a8d0000.can: 5a8d0000.can supply xceiver not found, using dummy regulator
[    0.304281] flexcan 5a8d0000.can (unnamed net_device) (uninitialized): Could not enable RX FIFO, unsupported core
[    0.314640] flexcan 5a8d0000.can: registering netdev failed
[    0.320728] flexcan 5a8e0000.can: 5a8e0000.can supply xceiver not found, using dummy regulator
[    0.320991] flexcan 5a8e0000.can (unnamed net_device) (uninitialized): Could not enable RX FIFO, unsupported core
[    0.331360] flexcan 5a8e0000.can: registering netdev failed
[    0.337444] flexcan 5a8f0000.can: 5a8f0000.can supply xceiver not found, using dummy regulator
[    0.337716] flexcan 5a8f0000.can (unnamed net_device) (uninitialized): Could not enable RX FIFO, unsupported core
[    0.348117] flexcan 5a8f0000.can: registering netdev failed

RX FIFO should be enabled after the FRZ/HALT are valid. But the current
code set RX FIFO enable and FRZ/HALT at the same time.

Fixes: e955cead03117 ("CAN: Add Flexcan CAN controller driver")
Signed-off-by: Joakim Zhang <qiangqing.zhang@xxxxxxx>
---
 drivers/net/can/flexcan.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 038fe1036df2..8ee9fa2f4161 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -1803,6 +1803,7 @@ static int register_flexcandev(struct net_device *dev)
 {
 	struct flexcan_priv *priv = netdev_priv(dev);
 	struct flexcan_regs __iomem *regs = priv->regs;
+	unsigned int timeout = FLEXCAN_TIMEOUT_US / 10;
 	u32 reg, err;
 
 	err = flexcan_clks_enable(priv);
@@ -1825,10 +1826,19 @@ static int register_flexcandev(struct net_device *dev)
 	if (err)
 		goto out_chip_disable;
 
-	/* set freeze, halt and activate FIFO, restrict register access */
+	/* set freeze, halt and polling the freeze ack */
 	reg = priv->read(&regs->mcr);
-	reg |= FLEXCAN_MCR_FRZ | FLEXCAN_MCR_HALT |
-		FLEXCAN_MCR_FEN | FLEXCAN_MCR_SUPV;
+	reg |= FLEXCAN_MCR_FRZ | FLEXCAN_MCR_HALT;
+	priv->write(reg, &regs->mcr);
+
+	while (timeout-- && !(priv->read(&regs->mcr) & FLEXCAN_MCR_FRZ_ACK))
+		udelay(100);
+
+	if (!(priv->read(&regs->mcr) & FLEXCAN_MCR_FRZ_ACK))
+		return -ETIMEDOUT;
+
+	/* Activate FIFO, restrict register access */
+	reg |=  FLEXCAN_MCR_FEN | FLEXCAN_MCR_SUPV;
 	priv->write(reg, &regs->mcr);
 
 	/* Currently we only support newer versions of this core
-- 
2.17.1