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i.MX6UL FlexCAN Kernel Panic with Transceiver in Standby and Transmit Attempted

Question asked by Matthew Starr on Feb 22, 2016
Latest reply on Mar 7, 2016 by Matthew Starr

I am working with a custom i.MX6UL based board using the FlexCAN driver for CAN on both the imx_3.14.38_6ul_ga with 9x9_patch and imx_3.14.52_1.1.0_ga kernels.  The problem I am encountering is when the CAN transceiver is placed into Standby mode and I try to transmit a message, I get a kernel panic.

 

I am initializing both SocketCAN interfaces using the following commands:

/sbin/ip link set can0 type can restart-ms 100

/sbin/ip link set can0 up type can bitrate 250000

/sbin/ifconfig can0 txqueuelen 1000

/sbin/ip link set can1 type can restart-ms 100

/sbin/ip link set can1 up type can bitrate 250000

/sbin/ifconfig can1 txqueuelen 1000

 

The CAN transceivers are hard wired on, so I did not configure a xceiver-supply in the boards .dts file.  Here are the relevant sections of the custom board's .dts file for CAN:

&flexcan1 {

        pinctrl-names = "default";

        pinctrl-0 = <&pinctrl_flexcan1>;

        status = "okay";

};

 

&flexcan2 {

        pinctrl-names = "default";

        pinctrl-0 = <&pinctrl_flexcan2>;

        status = "okay";

};

 

pinctrl_flexcan1: flexcan1grp{

     fsl,pins = <

          MX6UL_PAD_UART3_RTS_B__FLEXCAN1_RX      0x1f0b0 /* MPU_CAN1_RXD */

          MX6UL_PAD_UART3_CTS_B__FLEXCAN1_TX      0x1f0b0 /* MPU_CAN1_TXD */

     >;

};

 

pinctrl_flexcan2: flexcan2grp{

     fsl,pins = <

          MX6UL_PAD_UART2_RTS_B__FLEXCAN2_RX      0x1f0b0 /* MPU_CAN2_RXD */

          MX6UL_PAD_UART2_CTS_B__FLEXCAN2_TX      0x1f0b0 /* MPU_CAN2_TXD */

     >;

};

 

Here is the kernel panic output I get when I attempt to send a message using cansend:

# cansend can0 500#11.22.33.44

# BUG: scheduling while atomic: swapper/0/0x00000100

Unable to handle kernel NULL pointer dereference at virtual address 00000000

pgd = 80004000

[00000000] *pgd=00000000

Internal error: Oops: 80000007 [#1] ARM

Modules linked in:

CPU: 0 PID: 0 Comm: swapper Not tainted 3.14.52 #1

task: 807e9ca0 ti: 807de000 task.ti: 807de000

PC is at 0x0

LR is at try_to_wake_up+0x48/0xf8

pc : [<00000000>]    lr : [<8004d09c>]    psr: 00070193

sp : 807dfb88  ip : 00000015  fp : 807dfb9c

r10: 807f1018  r9 : 00000003  r8 : 00000001

r7 : 00000004  r6 : 2bcbbd04  r5 : 60070193  r4 : 807e9ca0

r3 : 00000000  r2 : 00000001  r1 : 807e9ca0  r0 : 807f1460

Flags: nzcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel

Control: 10c53c7d  Table: 87924059  DAC: 00000015

Process swapper (pid: 0, stack limit = 0x807de230)

Stack: (0x807dfb88 to 0x807e0000)

fb80:                   807dfde8 807f1048 807dfde8 807f1048 807f1018 80047f34

fba0: 80047f14 80048254 00000000 807f1018 00000000 80048994 ffffffff 7fffffff

fbc0: 2bcbbd04 00000004 00000000 00000000 ffffffff 7fffffff 2bcbbd04 00000004

fbe0: 2bcbbd04 00000004 00000010 00000001 00000057 00000000 00000000 00000057

fc00: 84008b80 8082bad2 00000000 8001aafc 807ebd80 800588f8 00000000 8082b050

fc20: 84008b80 00000057 807dff68 f4a02000 80831486 00000006 00000000 800589e8

fc40: 84008b80 8005b100 00000057 800580d8 807fb2f4 8000e9c8 f4a0200c 807e6424

fc60: 807dfc80 80008550 00000000 80056a84 60070113 ffffffff 807dfcb4 80011ac0

fc80: 00000001 807f1bec 807f2844 60070113 00000032 807f1b88 00000000 00000000

fca0: 80831486 00000006 00000000 00000000 00000000 807dfcc8 00000000 80056a84

fcc0: 60070113 ffffffff 00000000 00000000 00000000 00000000 80831486 00000032

fce0: 60070113 00000000 00000000 00000001 00000003 00000000 807e9ca0 807f1460

fd00: 807f1460 807de010 8082ebc0 8082bacf 807dfd4c 80599d78 806c6cf0 807dfd34

fd20: 00000001 807dfd34 00000000 8004beb0 806c6cf0 807e9ee0 00000000 00000100

fd40: 00000002 807de018 807dfdd4 8059e0bc c1103780 2b864677 807f1048 2b864677

fd60: 00000004 80065e70 00000000 2b85f857 00000004 807f1018 807f1048 80048738

fd80: 00002710 00000000 ffffffff 00000000 2b864677 00000004 80872140 807de018

fda0: 00000001 00004e20 00000000 00002710 8082ebc0 807de018 00000001 00004e20

fdc0: 00000000 00002710 8082ebc0 8082ea44 8082ea40 8059dbf4 00002710 00000001

fde0: 00004e20 00000000 807dfde8 00000000 00000000 00000000 2b864677 00000004

fe00: 2b861f67 00000004 80047f14 807f1048 00000002 00000000 00000000 807f0710

fe20: 87990280 00000002 8419e800 88988000 00000004 807e6040 8082ebc0 80036084

fe40: 00002710 00000000 88988000 8033d8e8 00000001 8419e800 8419e800 807de000

fe60: 00000100 8033a640 8082ebc0 8082ea44 8082ea40 8033de54 00000001 8419e800

fe80: 00000000 8033a6d4 807de000 879902c8 807dfea0 807de020 00000000 800365ec

fea0: 2b940b34 00000004 807dfec0 00000000 00200200 807f0710 8082f3d0 80036774

fec0: 807dfec0 807dfec0 00015200 40000001 00000000 00000100 00000001 807de028

fee0: 807de000 800311b4 00000001 00015200 8082ea40 807f1928 8082ea00 0000000a

ff00: 805a25b8 ffff91d0 807f0710 00200000 00000000 807de038 00000057 00000000

ff20: f4a02000 8082bad0 807de000 00000000 00000000 80031514 807fb2f4 8000e9cc

ff40: f4a0200c 807e6424 807dff68 80008550 8000eb84 8000eb88 60070013 ffffffff

ff60: 807dff9c 80011ac0 00000000 807f1f70 00000000 80019fe0 807de000 807e60e8

ff80: 807de038 8082bad0 8082bad0 807de000 00000000 00000000 01000000 807dffb0

ffa0: 8000eb84 8000eb88 60070013 ffffffff 807f1f70 80058060 ffffffff 807909ec

ffc0: ffffffff ffffffff 80790500 00000000 00000000 807d559c 00000000 10c53c7d

ffe0: 807e6070 807d5598 807eadc0 80004059 410fc075 80008070 00000000 00000000

[<8004d09c>] (try_to_wake_up) from [<80047f34>] (hrtimer_wakeup+0x20/0x28)

[<80047f34>] (hrtimer_wakeup) from [<80048254>] (__run_hrtimer.isra.35+0x38/0xdc)

[<80048254>] (__run_hrtimer.isra.35) from [<80048994>] (hrtimer_interrupt+0xf0/0x294)

[<80048994>] (hrtimer_interrupt) from [<8001aafc>] (mxc_timer_interrupt+0x2c/0x34)

[<8001aafc>] (mxc_timer_interrupt) from [<800588f8>] (handle_irq_event_percpu+0xd0/0x198)

[<800588f8>] (handle_irq_event_percpu) from [<800589e8>] (handle_irq_event+0x28/0x38)

[<800589e8>] (handle_irq_event) from [<8005b100>] (handle_fasteoi_irq+0x70/0x130)

[<8005b100>] (handle_fasteoi_irq) from [<800580d8>] (generic_handle_irq+0x2c/0x3c)

[<800580d8>] (generic_handle_irq) from [<8000e9c8>] (handle_IRQ+0x38/0x84)

[<8000e9c8>] (handle_IRQ) from [<80008550>] (gic_handle_irq+0x2c/0x54)

[<80008550>] (gic_handle_irq) from [<80011ac0>] (__irq_svc+0x40/0x50)

Exception stack(0x807dfc80 to 0x807dfcc8)

fc80: 00000001 807f1bec 807f2844 60070113 00000032 807f1b88 00000000 00000000

fca0: 80831486 00000006 00000000 00000000 00000000 807dfcc8 00000000 80056a84

fcc0: 60070113 ffffffff

[<80011ac0>] (__irq_svc) from [<80056a84>] (vprintk_emit+0x150/0x418)

[<80056a84>] (vprintk_emit) from [<80599d78>] (printk+0x34/0x44)

[<80599d78>] (printk) from [<8004beb0>] (__schedule_bug+0x44/0x64)

[<8004beb0>] (__schedule_bug) from [<8059e0bc>] (__schedule+0x31c/0x3d4)

[<8059e0bc>] (__schedule) from [<8059dbf4>] (schedule_hrtimeout_range_clock+0xb4/0x140)

[<8059dbf4>] (schedule_hrtimeout_range_clock) from [<80036084>] (usleep_range+0x48/0x50)

[<80036084>] (usleep_range) from [<8033d8e8>] (flexcan_chip_start+0x64/0x3ac)

[<8033d8e8>] (flexcan_chip_start) from [<8033de54>] (flexcan_set_mode+0x14/0x60)

[<8033de54>] (flexcan_set_mode) from [<8033a6d4>] (can_restart+0x94/0xc8)

[<8033a6d4>] (can_restart) from [<800365ec>] (call_timer_fn.isra.42+0x24/0x88)

[<800365ec>] (call_timer_fn.isra.42) from [<80036774>] (run_timer_softirq+0x124/0x198)

[<80036774>] (run_timer_softirq) from [<800311b4>] (__do_softirq+0x114/0x21c)

[<800311b4>] (__do_softirq) from [<80031514>] (irq_exit+0xa8/0xf0)

[<80031514>] (irq_exit) from [<8000e9cc>] (handle_IRQ+0x3c/0x84)

[<8000e9cc>] (handle_IRQ) from [<80008550>] (gic_handle_irq+0x2c/0x54)

[<80008550>] (gic_handle_irq) from [<80011ac0>] (__irq_svc+0x40/0x50)

Exception stack(0x807dff68 to 0x807dffb0)

ff60:                   00000000 807f1f70 00000000 80019fe0 807de000 807e60e8

ff80: 807de038 8082bad0 8082bad0 807de000 00000000 00000000 01000000 807dffb0

ffa0: 8000eb84 8000eb88 60070013 ffffffff

[<80011ac0>] (__irq_svc) from [<8000eb88>] (arch_cpu_idle+0x38/0x3c)

[<8000eb88>] (arch_cpu_idle) from [<80058060>] (cpu_startup_entry+0xb8/0xf4)

[<80058060>] (cpu_startup_entry) from [<807909ec>] (start_kernel+0x2bc/0x2c8)

Code: bad PC value

---[ end trace 0dc1441ba4a64f46 ]---

Kernel panic - not syncing: Fatal exception in interrupt

Rebooting in 1 seconds..

mxc_restart: Watchdog reset failed to assert reset

 

I have verified the existence of this problem on the i.MX6UL EVK board too with the exact same kernel panic details using the imx6ul-14x14-evk.dts device tree. I first verified the CAN was working correctly with CAN Standby low.  Then by running the following commands I put the CAN transceiver into standy, sent a message, and caused the kernel panic:

echo 251 > /sys/class/gpio/export

echo 1 > /sys/class/gpio/gpio251/value

cansend can0 500#11.22.33.44

 

Best Regards,

Matthew Starr

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