tree 4a48ab1154b7533dcaac831ff2dad0e10865efa1
parent f47edc6dab11801c2e97088ba7bbce042ded867c
author Ira Snyder <iws@ovro.caltech.edu> 1242772933 -0700
committer Li Yang <leoli@freescale.com> 1242982157 +0800

fsldma: fix "DMA halt timeout!" errors

When using the DMA controller from multiple threads at the same time, it is
possible to get lots of "DMA halt timeout!" errors printed to the kernel
log.

This occurs due to a race between fsl_dma_memcpy_issue_pending() and the
interrupt handler, fsl_dma_chan_do_interrupt(). Both call the
fsl_chan_xfer_ld_queue() function, which does not protect against
concurrent accesses to dma_halt() and dma_start().

The existing spinlock is moved to cover the dma_halt() and dma_start()
functions. Testing shows that the "DMA halt timeout!" errors disappear.

Signed-off-by: Ira W. Snyder <iws@ovro.caltech.edu>
Signed-off-by: Li Yang <leoli@freescale.com>