netdev - RE: flexcan introduced a DIV/0 in kernel

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Date:   Mon, 12 Apr 2021 01:56:44 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Koen Vandeputte <koen.vandeputte@...ymesh.com>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>
CC:     "wg@...ndegger.com" <wg@...ndegger.com>,
        "mkl@...gutronix.de" <mkl@...gutronix.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: RE: flexcan introduced a DIV/0 in kernel


Hi Koen, Mac,

Sorry about this regression, it has caused inconvenience to many people.

I tested the first version, but only double check the logic after improving the patch per Mac's advice.

I will keep in mind, test each version before upstream to avoid unexpected issues, sorry.

Best Regards,
Joakim Zhang

> -----Original Message-----
> From: Koen Vandeputte <koen.vandeputte@...ymesh.com>
> Sent: 2021年4月9日 18:18
> To: linux-can@...r.kernel.org
> Cc: wg@...ndegger.com; mkl@...gutronix.de; netdev@...r.kernel.org;
> Joakim Zhang <qiangqing.zhang@....com>; gregkh@...uxfoundation.org
> Subject: flexcan introduced a DIV/0 in kernel
> 
> Hi All,
> 
> I just updated kernel 4.14 within OpenWRT from 4.14.224 to 4.14.229 Booting
> it shows the splat below on each run. [1]
> 
> 
> It seems there are 2 patches regarding flexcan which were introduced in
> 4.14.226
> 
> --> ce59ffca5c49 ("can: flexcan: enable RX FIFO after FRZ/HALT valid")
> --> bb7c9039a396 ("can: flexcan: assert FRZ bit in
> --> flexcan_chip_freeze()")
> 
> Reverting these fixes the splat.
> 
> Hope this helps,
> 
> Koen
> 
> 
> 
> [1]
> 
> [   10.062140] flexcan 2090000.flexcan: 2090000.flexcan supply xceiver not
> found, using dummy regulator [   10.071631] Division by zero in kernel.
> [   10.075511] CPU: 0 PID: 1061 Comm: kmodloader Not tainted 4.14.229 #0
> [   10.081981] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> [   10.088529] Backtrace:
> [   10.091040] [<8010ba30>] (dump_backtrace) from [<8010bdd4>]
> (show_stack+0x18/0x1c)
> [   10.098631]  r7:9f5edc10 r6:60000013 r5:00000000 r4:80932c88
> [   10.104336] [<8010bdbc>] (show_stack) from [<8063f8e0>]
> (dump_stack+0x9c/0xb0)
> [   10.111591] [<8063f844>] (dump_stack) from [<8010bb90>]
> (__div0+0x1c/0x20)
> [   10.118491]  r7:9f5edc10 r6:a0f0c000 r5:9ea3fd40 r4:9ea3f800
> [   10.124199] [<8010bb74>] (__div0) from [<8063de94>] (Ldiv0+0x8/0x10)
> [   10.130611] [<7f32b334>] (flexcan_mailbox_read [flexcan]) from
> [<7f32c480>] (flexcan_probe+0x360/0x468 [flexcan])
> [   10.140902]  r7:9f5edc10 r6:a0f0c000 r5:9ea3fd40 r4:9ea3f800
> [   10.146608] [<7f32c120>] (flexcan_probe [flexcan]) from [<8040f384>]
> (platform_drv_probe+0x60/0xb4)
> [   10.155698]  r10:80903c08 r9:00000000 r8:0000000d r7:fffffdfb
> r6:7f32e014 r5:fffffffe
> [   10.163562]  r4:9f5edc10
> [   10.166117] [<8040f324>] (platform_drv_probe) from [<8040db78>]
> (driver_probe_device+0x154/0x2ec)
> [   10.175012]  r7:7f32e014 r6:00000000 r5:9f5edc10 r4:80964928
> [   10.180720] [<8040da24>] (driver_probe_device) from [<8040dd98>]
> (__driver_attach+0x88/0xac)
> [   10.189195]  r9:7f32e080 r8:014000c0 r7:00000000 r6:9f5edc44
> r5:7f32e014 r4:9f5edc10
> [   10.196985] [<8040dd10>] (__driver_attach) from [<8040bfc0>]
> (bus_for_each_dev+0x54/0xa8)
> [   10.205199]  r7:00000000 r6:8040dd10 r5:7f32e014 r4:00000000
> [   10.210891] [<8040bf6c>] (bus_for_each_dev) from [<8040d4ac>]
> (driver_attach+0x24/0x28)
> [   10.218912]  r6:9e41e880 r5:8091b340 r4:7f32e014 [   10.223559]
> [<8040d488>] (driver_attach) from [<8040d0a0>]
> (bus_add_driver+0xf4/0x204)
> [   10.231529] [<8040cfac>] (bus_add_driver) from [<8040e4e8>]
> (driver_register+0xb0/0xec)
> [   10.239574]  r7:7f331000 r6:00000000 r5:ffffe000 r4:7f32e014
> [   10.245266] [<8040e438>] (driver_register) from [<8040f2d4>]
> (__platform_driver_register+0x48/0x50)
> [   10.254332]  r5:ffffe000 r4:80903c08
> [   10.257953] [<8040f28c>] (__platform_driver_register) from [<7f331020>]
> (init_module+0x20/0x1000 [flexcan]) [   10.267729] [<7f331000>]
> (init_module [flexcan]) from [<80101a1c>]
> (do_one_initcall+0xc4/0x188)
> [   10.276490] [<80101958>] (do_one_initcall) from [<80192458>]
> (do_init_module+0x68/0x204)
> [   10.284615]  r9:7f32e080 r8:014000c0 r7:00000000 r6:9e48b640
> r5:9e4af000 r4:7f32e080
> [   10.292389] [<801923f0>] (do_init_module) from [<801944b4>]
> (load_module+0x1e1c/0x220c)
> [   10.300441]  r7:00000000 r6:9e4af1a8 r5:9e4af000 r4:9e8f3f30
> [   10.306158] [<80192698>] (load_module) from [<80194a00>]
> (SyS_init_module+0x15c/0x17c)
> [   10.314110]  r10:00000051 r9:000128ce r8:ffffe000 r7:001e545c
> r6:00000000 r5:a0f0945c
> [   10.321957]  r4:0000345c
> [   10.324541] [<801948a4>] (SyS_init_module) from [<801079e0>]
> (ret_fast_syscall+0x0/0x54)
> [   10.332663]  r10:00000080 r9:9e8f2000 r8:80107be4 r7:00000080
> r6:00000003 r5:00000000
> [   10.340511]  r4:00000000
> [   10.344089] flexcan 2090000.flexcan: device registered
> (reg_base=a0f0c000, irq=33)
>