On Thu, Aug 16, 2012 at 11:29:12PM +0100, Russell King wrote: > On Thu, Aug 16, 2012 at 05:44:29PM -0400, Matt Porter wrote: > > Add a DMA engine driver for the TI EDMA controller. This driver > > is implemented as a wrapper around the existing DaVinci private > > DMA implementation. This approach allows for incremental conversion > > of each peripheral driver to the DMA engine API. The EDMA driver > > supports slave transfers but does not yet support cyclic transfers. > > Have you looked at the virt-dma support? That should allow you to > avoid some common errors, like forgetting that stuff submitted but > not issued should not be started even if the channel is currently > running. I had previously skimmed it a bit and wrote it off as a helper for certain types of controllers. On your suggestion, I looked into it in detail and it does look to be a nice improvement on handling those types of errors...some of which I noticed were not being handled properly in my v1 version. I did a quick and dirty conversion of the EDMA driver to use virt-dma now and it also results in simplified handling of the descriptors and about a 10% code reduction. I'll do some clean up on this virt-dma-enabled version and post v2. One thing to note is that although I'm borrowing a lot from how you did the omap-dma.c driver, the EDMA implementation of issue_pending() cannot schedule a tasklet to send the descriptor to the hardware. The client drivers have to be sure that dma_async_issue_pending() results in the PaRAM set been written to the h/w before the driver specific DMA reqs are enabled. Enabling the DMA req before the PaRAM set is programmed results in an event error condition on this h/w. Ideally there would be a dma_status state to reflect that a descriptor has actually been written to the h/w so that client drivers can safely enable dma reqs where this is a requirement. Thanks, Matt -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
