On Wed, Mar 08, 2017 at 08:48:31PM +0100, Lars-Peter Clausen wrote: > When the DMA memory is mapped for reading from the device the associated > cachelines are invalidated without writeback. There is no guarantee that > the changes made to the devres_node have made it to main memory yet, or > is there? That is incorrect. Overlapping cache lines are always written back on transitions from CPU to device ownership of the buffer (eg, dma_map_*().) Updates that are made by the CPU on overlapping cache lines while the memory is mapped for DMA may end up doing one of two things: either overwriting the newly DMA'd data, or being lost altogether. In the case of devm_* list manipulations, these should only ever happen during device probe and tear down, and if DMA is active at those times, the driver is seriously buggy. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
