netdev - [PATCH 2/9] can: flexcan: fix timeout when set small bitrate

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Message-Id: <20190607211541.16095-3-mkl@pengutronix.de>
Date:   Fri,  7 Jun 2019 23:15:34 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, linux-can@...r.kernel.org,
        kernel@...gutronix.de, Joakim Zhang <qiangqing.zhang@....com>,
        Dong Aisheng <aisheng.dong@....com>,
        linux-stable <stable@...r.kernel.org>,
        Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH 2/9] can: flexcan: fix timeout when set small bitrate

From: Joakim Zhang <qiangqing.zhang@....com>

Current we can meet timeout issue when setting a small bitrate like
10000 as follows on i.MX6UL EVK board (ipg clock = 66MHZ, per clock =
30MHZ):

| root@...6ul7d:~# ip link set can0 up type can bitrate 10000

A link change request failed with some changes committed already.
Interface can0 may have been left with an inconsistent configuration,
please check.

| RTNETLINK answers: Connection timed out

It is caused by calling of flexcan_chip_unfreeze() timeout.

Originally the code is using usleep_range(10, 20) for unfreeze
operation, but the patch (8badd65 can: flexcan: avoid calling
usleep_range from interrupt context) changed it into udelay(10) which is
only a half delay of before, there're also some other delay changes.

After double to FLEXCAN_TIMEOUT_US to 100 can fix the issue.

Meanwhile, Rasmus Villemoes reported that even with a timeout of 100,
flexcan_probe() fails on the MPC8309, which requires a value of at least
140 to work reliably. 250 works for everyone.

Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
Reviewed-by: Dong Aisheng <aisheng.dong@....com>
Cc: linux-stable <stable@...r.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/can/flexcan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 1c66fb2ad76b..f97c628eb2ad 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -166,7 +166,7 @@
 #define FLEXCAN_MB_CNT_LENGTH(x)	(((x) & 0xf) << 16)
 #define FLEXCAN_MB_CNT_TIMESTAMP(x)	((x) & 0xffff)

-#define FLEXCAN_TIMEOUT_US		(50)
+#define FLEXCAN_TIMEOUT_US		(250)

 /* FLEXCAN hardware feature flags
  *
-- 
2.20.1