On Fri, 2017-03-31 at 18:55 +0100, Robin Murphy wrote: > On 31/03/17 04:27, Michael Ellerman wrote: > > > > Robin Murphy <robin.murphy@xxxxxxx> writes: > > > > > > > > Hi Roy, > > > > > > On 29/03/17 22:13, Roy Pledge wrote: > > > > > > > > Use the shared-memory-pool mechanism for frame queue descriptor and > > > > packed frame descriptor record area allocations. > > > Thanks for persevering with this - in my opinion it's now looking like > > > it was worth the effort :) > > > > > > AFAICS the ioremap_wc() that this leads to does appear to give back > > > something non-cacheable on PPC (assuming "pgprot_noncached_wc" isn't > > > horrendously misnamed), and "no-map" should rule out any cacheable > > > linear map alias existing, so it would seem that this approach should > > > avert Scott's concerns about attribute mismatches. > > How does 'no-map' translate into something being excluded from the > > linear mapping? > Reserved regions marked with "no-map" get memblock_remove()d by > early_init_dt_alloc_reserved_memory_arch(). As I understand things, the > linear map should only cover memblock areas, and it would be explicitly > violating the semantics of "no-map" to still cover such a region. Discontiguous memory isn't supported on these PPC chips. Everything up to memblock_end_of_DRAM() gets mapped -- and if that were to change, the fragmentation would waste TLB1 entries. This also breaks compatibility with existing device trees. I suggest putting an ifdef in the qbman driver to add the new scheme for non-PPC arches only. -Scott -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
