On Thu, Dec 17, 2009 at 11:45 AM, Kumar Gala <ga...@kernel.crashing.org> wrote: >> The specific case it is needed for Talitos/raid is a channel switch >> interrupt. The interrupt causes the cleanup operation to be run which will >> kick off any pending dependent operations on the xor channel. In the raid >> case we only have callbacks at the end of a chain, so we need the interrupt >> to kick the engine in an operation chain like xor->copy->xor->callback. > > Ok, I'm still confused as to how the DMA interrupt interacts with the > Talitos/raid side of things. The should be completely independent (separate > interrupts, separate IP blocks). >
To keep hardware implementation details out of md/raid the async_tx api provides support for managing cross-channel dependency chains. When the raid5 code submits a xor->copy->xor chain the api prepares all the descriptors across all the involved channels but then delays submission as needed to maintain ordering. So at a minimum we need two interrupts in this scenario one from Talitos to kick the submission of the copy-descriptor to fsldma when the first xor completes, and another one to kick the submission of the second xor-descriptor on Talitos when fsldma completes the copy. Needless to say it is more efficient when a channel has all the capabilities, but this channel switch mechanism has proven effective on iop3xx and ppc4xx. -- Dan -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
