when start up to phy driver,crashed,log like this:
[ 1.953977] 0x0000008d0000-0x000002000000 : "rootfs_data"
[ 1.969217] libphy: ipq40xx_mdio: probed
[ 12.642674] Unable to handle kernel NULL pointer dereference at virtual address 000000a4
[ 12.642705] pgd = c0204000
[ 12.649820] [000000a4] *pgd=00000000
[ 12.652345] Internal error: Oops: 5 [#1] SMP ARM
[ 12.656073] Modules linked in:
[ 12.660677] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.14.79 #0
[ 12.663540] Hardware name: Generic DT based system
[ 12.669703] task: cf830000 task.stack: cf82e000
[ 12.674308] PC is at ar40xx_probe+0x350/0x808
[ 12.678737] LR is at try_to_del_timer_sync+0x4c/0x58
[ 12.683245] pc : [<c05b5918>] lr : [<c0362f78>] psr: 60000013
[ 12.688281] sp : cf82fdf0 ip : 00000000 fp : 00000080
[ 12.694267] r10: 00000006 r9 : cf98b000 r8 : 00000000
[ 12.699478] r7 : c0a593f4 r6 : cfde80f4 r5 : cf98b010 r4 : cfbf8010
[ 12.704689] r3 : 00000002 r2 : 00000000 r1 : 00000000 r0 : cfbf8010
[ 12.711288] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
[ 12.717796] Control: 10c5387d Table: 8020406a DAC: 00000051
[ 12.724998] Process swapper/0 (pid: 1, stack limit = 0xcf82e210)
[ 12.730730] Stack: (0xcf82fdf0 to 0xcf830000)
[ 12.736807] fde0: 00000000 c0800cb0 c0a52b6c cfbf81e4
[ 12.741069] fe00: c032b3dc cf802b40 cf9c2a80 00000004 00098000 000987ff cfde84a0 00000200
[ 12.749229] fe20: 00000000 00000000 00000000 00000000 0c000000 0c07ffff cfde814c 00000200
[ 12.757388] fe40: 00000000 00000000 00000000 00000000 c0a19d3c cf98b010 c0a19d3c c0a5876c
[ 12.765549] fe60: 00000000 00000000 c0a19d3c 00000000 00000000 c0556fe4 c0a58768 cf98b010
[ 12.773708] fe80: c0a5876c c0555a24 cf98b010 c0a19d3c cf98b044 00000000 00000007 00000059
[ 12.781869] fea0: c0936f48 c0555c10 00000000 c0a19d3c c0555b84 c05541b8 cf817558 cf932eb4
[ 12.790027] fec0: c0a19d3c cf9b5d00 c0a16e30 c0555134 c08101b0 c09168e4 c0a19d3c c0a19d3c
[ 12.798188] fee0: 00000000 c09168f4 ffffe000 c0556354 c0a03c08 00000000 c09168f4 c03019dc
[ 12.806347] ff00: cf82ff24 00000000 00000000 c084e800 cfffce40 c084e820 0000005a c084e820
[ 12.814508] ff20: cfffce52 c033123c c084e12c c0805b7c 00000006 00000006 c07def04 00000000
[ 12.822665] ff40: c07e7d08 c07def78 cfffce52 c9571f93 00000000 c0a24000 c0a24000 c092c834
[ 12.830827] ff60: c092c83c 00000007 00000059 c0936f48 00000000 c0900dd8 00000006 00000006
[ 12.838984] ff80: 00000000 c09005ac 00000000 c071f93c 00000000 00000000 00000000 00000000
[ 12.847146] ffa0: 00000000 c071f944 00000000 c0307828 00000000 00000000 00000000 00000000
[ 12.855305] ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 12.863464] ffe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
[ 12.871636] [<c05b5918>] (ar40xx_probe) from [<c0556fe4>] (platform_drv_probe+0x34/0x70)
[ 12.879789] [<c0556fe4>] (platform_drv_probe) from [<c0555a24>] (really_probe+0x114/0x274)
[ 12.887946] [<c0555a24>] (really_probe) from [<c0555c10>] (__driver_attach+0x8c/0xb0)
[ 12.896018] [<c0555c10>] (__driver_attach) from [<c05541b8>] (bus_for_each_dev+0x4c/0xa0)
[ 12.903917] [<c05541b8>] (bus_for_each_dev) from [<c0555134>] (bus_add_driver+0xe8/0x200)
[ 12.912076] [<c0555134>] (bus_add_driver) from [<c0556354>] (driver_register+0xa8/0xe4)
[ 12.920236] [<c0556354>] (driver_register) from [<c03019dc>] (do_one_initcall+0xc0/0x184)
[ 12.928052] [<c03019dc>] (do_one_initcall) from [<c0900dd8>] (kernel_init_freeable+0x13c/0x1d0)
[ 12.936385] [<c0900dd8>] (kernel_init_freeable) from [<c071f944>] (kernel_init+0x8/0x114)
[ 12.944893] [<c071f944>] (kernel_init) from [<c0307828>] (ret_from_fork+0x14/0x2c)
[ 12.953221] Code: ebf6b729 e5942114 e3a01000 e1a00004 (e59230a4)
[ 12.960819] ---[ end trace 8e9900d345cfcbe7 ]---
[ 12.966850] Kernel panic - not syncing: Fatal exception
[ 12.971535] CPU1: stopping
[ 12.976474] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G D 4.14.79 #0
[ 12.979253] Hardware name: Generic DT based system
[ 12.986472] [<c030e774>] (unwind_backtrace) from [<c030ac9c>] (show_stack+0x10/0x14)
[ 12.991245] [<c030ac9c>] (show_stack) from [<c070c8a8>] (dump_stack+0x88/0x9c)
[ 12.999141] [<c070c8a8>] (dump_stack) from [<c030da80>] (handle_IPI+0xe4/0x18c)
[ 13.006172] [<c030da80>] (handle_IPI) from [<c030143c>] (gic_handle_irq+0x8c/0x90)
[ 13.013377] [<c030143c>] (gic_handle_irq) from [<c030b80c>] (__irq_svc+0x6c/0x90)
[ 13.021010] Exception stack(0xcf85bf80 to 0xcf85bfc8)
[ 13.028564] bf80: 00000001 00000000 00000000 c0313c60 ffffe000 c0a03c74 c0a03c28 00000000
[ 13.033605] bfa0: 00000000 410fc075 00000000 00000000 cf85bfc8 cf85bfd0 c0308108 c030810c
[ 13.041757] bfc0: 60000013 ffffffff
[ 13.049917] [<c030b80c>] (__irq_svc) from [<c030810c>] (arch_cpu_idle+0x34/0x38)
[ 13.053222] [<c030810c>] (arch_cpu_idle) from [<c0349778>] (do_idle+0xdc/0x1a0)
[ 13.060860] [<c0349778>] (do_idle) from [<c0349a98>] (cpu_startup_entry+0x18/0x1c)
[ 13.067889] [<c0349a98>] (cpu_startup_entry) from [<8030170c>] (0x8030170c)
[ 13.075525] CPU3: stopping
[ 13.082377] CPU: 3 PID: 0 Comm: swapper/3 Tainted: G D 4.14.79 #0
[ 13.085156] Hardware name: Generic DT based system
[ 13.092373] [<c030e774>] (unwind_backtrace) from [<c030ac9c>] (show_stack+0x10/0x14)
[ 13.097145] [<c030ac9c>] (show_stack) from [<c070c8a8>] (dump_stack+0x88/0x9c)
[ 13.105041] [<c070c8a8>] (dump_stack) from [<c030da80>] (handle_IPI+0xe4/0x18c)
[ 13.112072] [<c030da80>] (handle_IPI) from [<c030143c>] (gic_handle_irq+0x8c/0x90)
[ 13.119280] [<c030143c>] (gic_handle_irq) from [<c030b80c>] (__irq_svc+0x6c/0x90)
[ 13.126911] Exception stack(0xcf85ff80 to 0xcf85ffc8)
[ 13.134466] ff80: 00000001 00000000 00000000 c0313c60 ffffe000 c0a03c74 c0a03c28 00000000
[ 13.139506] ffa0: 00000000 410fc075 00000000 00000000 cf85ffc8 cf85ffd0 c0308108 c030810c
[ 13.147659] ffc0: 60000013 ffffffff
[ 13.155820] [<c030b80c>] (__irq_svc) from [<c030810c>] (arch_cpu_idle+0x34/0x38)
[ 13.159125] [<c030810c>] (arch_cpu_idle) from [<c0349778>] (do_idle+0xdc/0x1a0)
[ 13.166762] [<c0349778>] (do_idle) from [<c0349a98>] (cpu_startup_entry+0x18/0x1c)
[ 13.173793] [<c0349a98>] (cpu_startup_entry) from [<8030170c>] (0x8030170c)
[ 13.181426] CPU0: stopping
[ 13.188280] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G D 4.14.79 #0
[ 13.191060] Hardware name: Generic DT based system
[ 13.198275] [<c030e774>] (unwind_backtrace) from [<c030ac9c>] (show_stack+0x10/0x14)
[ 13.203048] [<c030ac9c>] (show_stack) from [<c070c8a8>] (dump_stack+0x88/0x9c)
[ 13.210944] [<c070c8a8>] (dump_stack) from [<c030da80>] (handle_IPI+0xe4/0x18c)
[ 13.217975] [<c030da80>] (handle_IPI) from [<c030143c>] (gic_handle_irq+0x8c/0x90)
[ 13.225182] [<c030143c>] (gic_handle_irq) from [<c030b80c>] (__irq_svc+0x6c/0x90)
[ 13.232814] Exception stack(0xc0a01f48 to 0xc0a01f90)
[ 13.240369] 1f40: 00000001 00000000 00000000 c0313c60 ffffe000 c0a03c74
[ 13.245409] 1f60: c0a03c28 00000000 00000000 c092ca28 cfffce00 00000000 c0a01f90 c0a01f98
[ 13.253565] 1f80: c0308108 c030810c 60000013 ffffffff
[ 13.261723] [<c030b80c>] (__irq_svc) from [<c030810c>] (arch_cpu_idle+0x34/0x38)
[ 13.266762] [<c030810c>] (arch_cpu_idle) from [<c0349778>] (do_idle+0xdc/0x1a0)
[ 13.274226] [<c0349778>] (do_idle) from [<c0349a98>] (cpu_startup_entry+0x18/0x1c)
[ 13.281258] [<c0349a98>] (cpu_startup_entry) from [<c0900c90>] (start_kernel+0x3b4/0x3c0)
[ 13.288898] [<c0900c90>] (start_kernel) from [<8020807c>] (0x8020807c)
[ 13.297142] Rebooting in 1 seconds..
[ 15.303715] Reboot failed -- System halted