On Thu, Mar 26, 2015 at 07:12:23AM -0700, Dan Williams wrote: > > + struct resource *res_mem; > > + int err; > > + > > + res_mem = request_mem_region_exclusive(pmem->phys_addr, pmem->size, > > + "pmem"); > > Isn't request_mem_region() enough? i.e. it seems > request_mem_region_exclusive() assumes no DAX, at least in theory? This is 1:1 from the patch Ross sent, but I've been wondering why request_mem_region_exclusive is used here. All it does is setting the IORESOURCE_EXCLUSIVE flag, which prevents /dev/mem and sysfs from accessing the memory while the driver claims it. Besides pmem only a watchdog driver and e1000 make use of this flag, and there's various function related to it that are entirely unused. It's a weird beast. > This is fine for now, but I think we're going to end up with a > continuum of solutions to this problem based on the platform and the > device. Some ADR platforms have firmware that takes actions like > flushing caches on a "power going away" signal. Other platforms have > cache management instructions that we can use on either a per-i/o or > per REQ_FUA/FLUSH request. Hmm, with this being in the memory map by > default I think this poses a challenge for VIVT caches and aliased > accesses? We can revisit this when arm support shows up. Yes, I expect us to pass flags related to this through the platform_data eventually, but I think that starting with the simplest and safest version is probably the best idea. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
