FlexCAN driver triggers kernel BUG in BUSOFF restart

[Marc Kleine-Budde]

I was asked by Freescale to post this kernel BUG to you and your email
address appears in the kernel documentation, so please accept my
apologies if you did not wish to see this.

Thanks for the bug report.

A kernel BUG is triggered during a CAN send operation (kernel version
3.15.7, stack trace follows below). A simple program, such as the one
included in the kernel's CAN documentation, will cause this problem, as
will the can-utils programs 'cangen' and 'cansend'.

[...]

BUG: scheduling while atomic: swapper/0/0/0x00000100
#0: (((&priv->restart_timer))){+.-...}, at: [<8002fe60>]
call_timer_fn+0x0/0xe8
CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 3.15.7 #5
[<80011ba4>] (dump_backtrace) from [<80011d40>] (show_stack+0x18/0x1c)
r6:00000000 r5:00000000 r4:00000000 r3:00000000
[<80011d28>] (show_stack) from [<805de120>] (dump_stack+0x88/0xa4)
[<805de098>] (dump_stack) from [<805db3ec>] (__schedule_bug+0x64/0x7c)
r5:80867268 r4:80867268
[<805db388>] (__schedule_bug) from [<805e09b0>] (__schedule+0x540/0x5f8)
r4:bf7c7b00 r3:00000002
[<805e0470>] (__schedule) from [<805e0b5c>] (schedule+0x38/0x88)
r10:8085c000 r9:00000000 r8:00000001 r7:00000000 r6:00004e20 r5:00000000
r4:00002710
[<805e0b24>] (schedule) from [<805e03c4>]
(schedule_hrtimeout_range_clock+0xe0/0x158)
[<805e02e4>] (schedule_hrtimeout_range_clock) from [<805e0450>]
(schedule_hrtimeout_range+0x14/0x18)
r10:808644c4 r8:bf335e00 r7:00000000 r6:c09b8000 r5:c09b8000 r4:bf335800
[<805e043c>] (schedule_hrtimeout_range) from [<8002fb58>]
(usleep_range+0x50/0x58)
[<8002fb08>] (usleep_range) from [<803f2964>]
(flexcan_chip_start+0x7c/0x440)
[<803f28e8>] (flexcan_chip_start) from [<803f3994>]
(flexcan_set_mode+0x28/0x54)

[...]

David Jander already provided a fix for this problem:

8badd65 can: flexcan: avoid calling usleep_range from interrupt context

It will hit mainline soon and then be backported to the stable trees.

Marc

---

From 8badd65e48c90d66587359d5329c2813088c0f50 Mon Sep 17 00:00:00 2001
From: David Jander <***@protonic.nl>
Date: Wed, 27 Aug 2014 12:02:16 +0200
Subject: [PATCH] can: flexcan: avoid calling usleep_range from interrupt
context

Apparently can_restart() runs from a (timer-) interrupt and can call
flexcan_chip_[en|dis]able(), so avoid using usleep_range()

Signed-off-by: David Jander <***@protonic.nl>
Cc: linux-stable <***@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <***@pengutronix.de>
---
drivers/net/can/flexcan.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 944aa5d..630c7bf 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -298,7 +298,7 @@ static int flexcan_chip_enable(struct flexcan_priv *priv)
flexcan_write(reg, &regs->mcr);

while (timeout-- && (flexcan_read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK))
- usleep_range(10, 20);
+ udelay(10);

if (flexcan_read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK)
return -ETIMEDOUT;
@@ -317,7 +317,7 @@ static int flexcan_chip_disable(struct flexcan_priv *priv)
flexcan_write(reg, &regs->mcr);

while (timeout-- && !(flexcan_read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK))
- usleep_range(10, 20);
+ udelay(10);

if (!(flexcan_read(&regs->mcr) & FLEXCAN_MCR_LPM_ACK))
return -ETIMEDOUT;
@@ -336,7 +336,7 @@ static int flexcan_chip_freeze(struct flexcan_priv *priv)
flexcan_write(reg, &regs->mcr);

while (timeout-- && !(flexcan_read(&regs->mcr) & FLEXCAN_MCR_FRZ_ACK))
- usleep_range(100, 200);
+ udelay(100);

if (!(flexcan_read(&regs->mcr) & FLEXCAN_MCR_FRZ_ACK))
return -ETIMEDOUT;
@@ -355,7 +355,7 @@ static int flexcan_chip_unfreeze(struct flexcan_priv *priv)
flexcan_write(reg, &regs->mcr);

while (timeout-- && (flexcan_read(&regs->mcr) & FLEXCAN_MCR_FRZ_ACK))
- usleep_range(10, 20);
+ udelay(10);

if (flexcan_read(&regs->mcr) & FLEXCAN_MCR_FRZ_ACK)
return -ETIMEDOUT;
@@ -370,7 +370,7 @@ static int flexcan_chip_softreset(struct flexcan_priv *priv)

flexcan_write(FLEXCAN_MCR_SOFTRST, &regs->mcr);
while (timeout-- && (flexcan_read(&regs->mcr) & FLEXCAN_MCR_SOFTRST))
- usleep_range(10, 20);
+ udelay(10);

if (flexcan_read(&regs->mcr) & FLEXCAN_MCR_SOFTRST)
return -ETIMEDOUT;