Messages in this thread | | | Subject | Re: ISA DMA controller hangs | From | Alan Cox <> | Date | Sat, 28 May 2005 14:51:26 +0100 |
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On Sad, 2005-05-28 at 14:38, Pierre Ossman wrote: > I've been having some problems with ISA DMA transfers failing. They work > fine until the machine does a suspend-to-ram. After that all DMA > transfers stall. Does perhaps the DMA controller need a kick in the *** > after a suspend? I'm no expert on the ISA DMA controller so I could use > some help here.
The DMA controller has some bits of state which are potentially in need of restoration as well as a need to ensure you don't suspend while it is running I would imagine. Even for bus masters I believe you would need to restore the DMA enable bits.
See include/asm-i386/dma.h but note that some registers have side effects and the dma_outb etc are used to get required delays on some PCs
Alan
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