Messages in this thread | | | Subject | Re: [PATCH 2/3] ARM/keystone: move the DMA offset handling under ifdef CONFIG_ARM_LPAE | From | Robin Murphy <> | Date | Fri, 11 Sep 2020 12:27:21 +0100 |
| |
On 2020-09-11 12:15, Russell King - ARM Linux admin wrote: > On Thu, Sep 10, 2020 at 07:40:37AM +0200, Christoph Hellwig wrote: >> The DMA offset notifier can only be used if PHYS_OFFSET is at least >> KEYSTONE_HIGH_PHYS_START, which can't be represented by a 32-bit >> phys_addr_t. Currently the code compiles fine despite that, a pending >> change to the DMA offset handling would create a compiler warning for >> this case. Add an ifdef to not compile the code except for LPAE >> configs. > > However, to have use of the high physical offset, LPAE needs to be > enabled, which ensures that phys_addr_t is 64-bit. > > I believe that DMA is non-coherent on this platform unless the high > physical address is used. Or something like that.
Yeah, it's probably not a configuration that anyone would actually want to use in anger on Keystone itself, but as long as folks might have ARCH_KEYSTONE selected in their non-LPAE multiplatform config we should avoid build regressions. I did wonder if Keystone should simply have a hard dependency on LPAE, but there does appear to be some explicit support for running directly from the non-coherent low 2G alias :/
Robin.
| |