From: David Brownell <dbrownell@xxxxxxxxxxxxxxxxxxxxx>
At91_mci is abusing dma_free_coherent(), which may not be called
with IRQs disabled. I saw "mkfs.ext3" on an MMC card objecting
voluminously as each write completed:
WARNING: at arch/arm/mm/consistent.c:368 dma_free_coherent+0x2c/0x224()
[<c002726c>] (dump_stack+0x0/0x14) from [<c00387d4>] (warn_on_slowpath+0x4c/0x68)
[<c0038788>] (warn_on_slowpath+0x0/0x68) from [<c0028768>] (dma_free_coherent+0x2c/0x224)
r6:00008008 r5:ffc06000 r4:00000000
[<c002873c>] (dma_free_coherent+0x0/0x224) from [<c01918ac>] (at91_mci_irq+0x374/0x420)
[<c0191538>] (at91_mci_irq+0x0/0x420) from [<c0065d9c>] (handle_IRQ_event+0x2c/0x6c)
...
This bug has been around for a LONG time. The MM warning is
from late 2005, but the driver merged a year later ... so I'm
puzzled why nobody noticed this before now.
The fix involves noting that this buffer shouldn't be DMA-coherent;
it's just used for normal DMA writes. So replace it with standard
kmalloc() buffering and DMA mapping calls.
This is the quickie fix. A better one would not rely on allocating
large bounce buffers. (Note that dma_alloc_coherent could have failed
too, but that case was ignored... kmalloc is a bit more likely to
fail though.)
Signed-off-by: David Brownell <dbrownell@xxxxxxxxxxxxxxxxxxxxx>