Messages in this thread | | | Date | Thu, 22 Sep 2022 23:05:10 +0900 | Subject | Re: [PATCH v5 2/5] iommu/io-pgtable: Move Apple DART support to its own file | From | Hector Martin <> |
| |
On 16/09/2022 18.41, Janne Grunau wrote: > The pte format used by the DARTs found in the Apple M1 (t8103) is not > fully compatible with io-pgtable-arm. The 24 MSB are used for subpage > protection (mapping only parts of page) and conflict with the address > mask. In addition bit 1 is not available for tagging entries but disables > subpage protection. Subpage protection could be useful to support a CPU > granule of 4k with the fixed IOMMU page size of 16k. > > The DARTs found on Apple M1 Pro/Max/Ultra use another different pte > format which is even less compatible. To support an output address size > of 42 bit the address is shifted down by 4. Subpage protection is > mandatory and bit 1 signifies uncached mappings used by the display > controller. > > It would be advantageous to share code for all known Apple DART > variants to support common features. The page table allocator for DARTs > is less complex since it uses a two levels of translation table without > support for huge pages. > > Signed-off-by: Janne Grunau <j@jannau.net> > Acked-by: Robin Murphy <robin.murphy@arm.com> > Acked-by: Sven Peter <sven@svenpeter.dev> > > ---
[...]
> +static void *__dart_alloc_pages(size_t size, gfp_t gfp, > + struct io_pgtable_cfg *cfg) > +{ > + struct device *dev = cfg->iommu_dev; > + int order = get_order(size); > + struct page *p; > + > + VM_BUG_ON((gfp & __GFP_HIGHMEM)); > + p = alloc_pages(gfp | __GFP_ZERO, order); > + if (!p) > + return NULL; > + > + return page_address(p); > +}
This throws a warning:
drivers/iommu/io-pgtable-dart.c: In function ‘__dart_alloc_pages’: drivers/iommu/io-pgtable-dart.c:112:24: warning: unused variable ‘dev’ [-Wunused-variable] 112 | struct device *dev = cfg->iommu_dev; | ^~~
The fix is trivial, of course.
- Hector
| |