David Brownell wrote:
>> Here is an occurrence of it:
>> WARNING: at arch/arm/mm/consistent.c:364 dma_free_coherent()
>> [<c0025d8c>] (dump_stack+0x0/0x14) from [<c0027034>]
>> (dma_free_coherent+0x38/0x200)
>> [<c0026ffc>] (dma_free_coherent+0x0/0x200) from [<c002b5bc>]
>> (dma_unmap_single+0x144/0x164)
>> [<c002b478>] (dma_unmap_single+0x0/0x164) from [<bf003b9c>]
>>
>
> Obviously, whoever implemented dma_unmap_single() in terms of calls
> to dma_free_coherent() is the source of this particular problem.
>
>
>
Right, and it is defined in arch/arm/common/dmabounce.c:
/*
* see if a mapped address was really a "safe" buffer and if so, copy
* the data from the safe buffer back to the unsafe buffer and free up
* the safe buffer. (basically return things back to the way they
* should be)
*/
void
dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
enum dma_data_direction dir)
{
dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
__func__, (void *) dma_addr, size, dir);
BUG_ON(dir == DMA_NONE);
unmap_single(dev, dma_addr, size, dir);
}
I am trying to understand dmabounce, why this problem occurs, and how to
correct it
I hope with the help of linux-arm people...
>> (usb_hcd_giveback_urb+0xb0/0x108 [usbcore])
>> r7:c08633e0 r6:c1190800 r5:c08633e0 r4:00000001
>> [<bf003aec>] (usb_hcd_giveback_urb+0x0/0x108 [usbcore]) from
>> [<bf02a6b4>] (ehci_urb_done+0x78/0x80 [ehci_hcd])
>> r6:c11908bc r5:c11908bc r4:c08633e0
>> [<bf02a63c>] (ehci_urb_done+0x0/0x80 [ehci_hcd]) from [<bf02c290>]
>> (ehci_work+0x474/0x79c [ehci_hcd])
>> r5:c084e2a0 r4:ffc28180
>> [<bf02be1c>] (ehci_work+0x0/0x79c [ehci_hcd]) from [<bf02df50>]
>> (ehci_watchdog+0x64/0x6c [ehci_hcd])
>> [<bf02deec>] (ehci_watchdog+0x0/0x6c [ehci_hcd]) from [<c003fcb0>]
>> (run_timer_softirq+0x14c/0x1e0)
>> r5:00000100 r4:c02914a0
>> [<c003fb64>] (run_timer_softirq+0x0/0x1e0) from [<c003c028>]
>> (__do_softirq+0x5c/0xd0)
>> r7:c02a7314 r6:0000000a r5:c0291284 r4:00000001
>> [<c003bfcc>] (__do_softirq+0x0/0xd0) from [<c003c3f4>] (irq_exit+0x44/0x4c)
>> r6:00000000 r5:c0278144 r4:00000005
>> [<c003c3b0>] (irq_exit+0x0/0x4c) from [<c0021048>]
>> (__exception_text_start+0x48/0x60)
>> [<c0021000>] (__exception_text_start+0x0/0x60) from [<c0021a24>]
>> (__irq_svc+0x24/0x80)
>> Exception stack(0xc0271f64 to 0xc0271fac)
>> 1f60: c0885580 00000002 c0270000 00000000 c0022f50 c0270000
>> c001ff50
>> 1f80: c02a7314 0001e0ec 690541f1 0001dee4 c0271fc0 c0271fac c0271fac
>> c0022d30
>> 1fa0: c0022d38 60000013
>> ffffffff
>> r6:00000020 r5:0000001f r4:ffffffff
>> [<c0022cf8>] (cpu_idle+0x0/0x54) from [<c01e5ad8>] (rest_init+0x48/0x58)
>> r5:c028b828 r4:c029446c
>> [<c01e5a90>] (rest_init+0x0/0x58) from [<c0008bd8>]
>> (start_kernel+0x280/0x2ec)
>> [<c0008958>] (start_kernel+0x0/0x2ec) from [<00008030>] (0x8030)
>>
>
>
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