On Thursday 25 June 2015 15:01:56 Casey Leedom wrote: > > Is there a reference I can read on this so I can understand > when and where we can use the __raw_*() APIs? Can these > Raw Read/Write operations be reordered with respect to > each other or are the use of the various flavors of SYNC > instructions just to maintain order between Cached Memory > Accesses and I/O Instructions? The interpretation is not consistent across architectures. My best description would be that the __raw_*() accessors should only be used for accessing RAM areas that are known to have no side-effects and can be read in any size (8-bit to 64-bit wide), any alignment, and do not have a specific endianess. If you are dealing with MMIO registers that have a fixed endianess and size, the correct accessor would be readl_relaxed(), which is like readl() but lacks the barriers on certain architectures. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
