On Tue, 2018-03-27 at 10:42 +0100, Will Deacon wrote: > > > > This example adds a wmb() between two writes to a coherent DMA > > area, it is definitely required there. I'm pretty sure I've never seen > > any bug reports pointing to a missing wmb() between memory > > and MMIO write accesses, but if you remember seeing them in the > > list, maybe you can look again for some evidence of something going > > wrong on x86 without it? > > If this is just about ordering accesses to coherent DMA, then using > dma_wmb() instead will be much better performance on arm/arm64. Ah, something we should look into for powerpc as well, as we could use an lwsync for that which is also cheaper than a full sync wmb does. dma_wmb() is basically the same as smp_wmb() without the CONFIG_SMP conditional right ? Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
