rk3188 emac stuck at high load

[Shuyu Wei]

Hi,
I'm testing Radxa Rock Pro board with mainline kernel 4.4.0-rc6. 
The problem can be reproduced by simultaneously wget two large files at high speed to /dev/null.

$wget https://192.168.1.1/file.bin -O /dev/null -q &
$wget https://192.168.1.1/file.bin -O /dev/null

or open two sftp session to download two large files to /dev/null.

Some addtional information that might help:
    Downloading from encrypted https links or sftp server triggers the problem much easier.
    Disabling SMP in kernel seems to fix the problem.
    Sometimes the emac just stops sending and receiving frames, sometimes it produces kernel panics like below.

[ 2191.975729] BUG: Bad page state in process swapper/0  pfn:8d960
[ 2191.982354] page:ef463180 count:-1 mapcount:0 mapping:  (null) index:0x0
[ 2191.989047] flags: 0x0()
[ 2191.991594] page dumped because: nonzero _count
[ 2191.996127] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.0-rc6 #114
[ 2192.002475] Hardware name: Rockchip (Device Tree)
[ 2192.007174] Backtrace: 
[ 2192.009658] [<c00134d4>] (dump_backtrace) from [<c0013680>] (show_stack+0x18/0x1c)
[ 2192.017220]  r7:c051c4f8 r6:ef463180 r5:c05b7000 r4:00000000
[ 2192.022948] [<c0013668>] (show_stack) from [<c0219d90>] (dump_stack+0x90/0xa0)
[ 2192.030176] [<c0219d00>] (dump_stack) from [<c00b2cd4>] (bad_page+0xdc/0x12c)
[ 2192.037302]  r5:c059a100 r4:c05f430c
[ 2192.040913] [<c00b2bf8>] (bad_page) from [<c00b606c>] (get_page_from_freelist+0x388/0x95c)
[ 2192.049166]  r9:00000008 r8:ef463180 r7:c051c4d0 r6:00000000 r5:00000000 r4:c051c4e4
[ 2192.056982] [<c00b5ce4>] (get_page_from_freelist) from [<c00b6880>] (__alloc_pages_nodemask+0xd8/0x8e8)
[ 2192.066362]  r10:c001b068 r9:00000000 r8:ee0b02b0 r7:60000113 r6:00000003 r5:02095220
[ 2192.074254]  r4:c05ca1c0
[ 2192.076809] [<c00b67a8>] (__alloc_pages_nodemask) from [<c00b7140>] (__alloc_page_frag+0xb0/0x160)
[ 2192.085757]  r10:c001b068 r9:00000000 r8:ee0b02b0 r7:60000113 r6:02080020 r5:00000740
[ 2192.093650]  r4:eedbc884
[ 2192.096207] [<c00b7090>] (__alloc_page_frag) from [<c03273b4>] (__netdev_alloc_skb+0xa0/0x104)
[ 2192.104806]  r7:60000113 r6:eedbc884 r5:ee0b0000 r4:00000740
[ 2192.110525] [<c0327314>] (__netdev_alloc_skb) from [<c02aac00>] (arc_emac_poll+0x318/0x57c)
[ 2192.118865]  r9:00000000 r8:ee0b02b0 r7:0000019c r6:ee163780 r5:00000670 r4:ee0b0000
[ 2192.126683] [<c02aa8e8>] (arc_emac_poll) from [<c0339ed8>] (net_rx_action+0x1f0/0x2ec)
[ 2192.134590]  r10:c0599df8 r9:c059a100 r8:00073760 r7:0000012c r6:00000028 r5:c02aa8e8
[ 2192.142483]  r4:ee0b04e0
[ 2192.145040] [<c0339ce8>] (net_rx_action) from [<c0026f5c>] (__do_softirq+0x134/0x258)
[ 2192.152860]  r10:c059a080 r9:40000003 r8:00000003 r7:00000100 r6:c0598000 r5:c059a08c
[ 2192.160751]  r4:00000000
[ 2192.163303] [<c0026e28>] (__do_softirq) from [<c0027344>] (irq_exit+0xb8/0x120)
[ 2192.170604]  r10:c04818a4 r9:c059a4a0 r8:ee808000 r7:00000000 r6:00000000 r5:0000001a
[ 2192.178496]  r4:c05943bc
[ 2192.181051] [<c002728c>] (irq_exit) from [<c00656a4>] (__handle_domain_irq+0x68/0xbc)
[ 2192.188871]  r5:0000001a r4:c05943bc
[ 2192.192479] [<c006563c>] (__handle_domain_irq) from [<c0009438>] (gic_handle_irq+0x40/0x78)
[ 2192.200818]  r9:c059a4a0 r8:f0803100 r7:f0802100 r6:c0599f00 r5:f080210c r4:c059a87c
[ 2192.208630] [<c00093f8>] (gic_handle_irq) from [<c0014214>] (__irq_svc+0x54/0x70)
[ 2192.216105] Exception stack(0xc0599f00 to 0xc0599f48)
[ 2192.221161] 9f00: 00000001 00000000 00000000 c001e940 c0598000 c059a454 00000000 c05ca291
[ 2192.229336] 9f20: 00000000 c059a4a0 c04818a4 c0599f5c c0599f60 c0599f50 c0010208 c001020c
[ 2192.237505] 9f40: 60000013 ffffffff
[ 2192.240990]  r9:c059a4a0 r8:00000000 r7:c0599f34 r6:ffffffff r5:60000013 r4:c001020c
[ 2192.248810] [<c00101cc>] (arch_cpu_idle) from [<c005bbec>] (default_idle_call+0x28/0x34)
[ 2192.256899] [<c005bbc4>] (default_idle_call) from [<c005be60>] (cpu_startup_entry+0x214/0x270)
[ 2192.265515] [<c005bc4c>] (cpu_startup_entry) from [<c047a6f4>] (rest_init+0x80/0x84)
[ 2192.273248]  r7:ffffffff
[ 2192.275808] [<c047a674>] (rest_init) from [<c055fca0>] (start_kernel+0x348/0x354)
[ 2192.283288] [<c055f958>] (start_kernel) from [<60008078>] (0x60008078)
[ 2192.289798] Disabling lock debugging due to kernel taint
[ 2192.300779] rockchip_emac 10204000.ethernet eth0: BUG! Tx Ring full when queue awake!

I'm glad to provide more information if needed.

Shuyu Wei