From: Hector Martin <marcan@marcan.st> To: Janne Grunau <j@jannau.net>, iommu@lists.linux.dev Cc: Konrad Dybcio <konrad.dybcio@somainline.org>, asahi@lists.linux.dev, Robin Murphy <robin.murphy@arm.com>, Sven Peter <sven@svenpeter.dev>, Alyssa Rosenzweig <alyssa@rosenzweig.io>, Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 2/5] iommu/io-pgtable: Move Apple DART support to its own file Date: Thu, 22 Sep 2022 23:05:10 +0900 [thread overview] Message-ID: <ff713226-333c-72e6-da79-7f0b54b6d15d@marcan.st> (raw) In-Reply-To: <20220916094152.87137-3-j@jannau.net> 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
WARNING: multiple messages have this Message-ID (diff)
From: Hector Martin <marcan@marcan.st> To: Janne Grunau <j@jannau.net>, iommu@lists.linux.dev Cc: Konrad Dybcio <konrad.dybcio@somainline.org>, asahi@lists.linux.dev, Robin Murphy <robin.murphy@arm.com>, Sven Peter <sven@svenpeter.dev>, Alyssa Rosenzweig <alyssa@rosenzweig.io>, Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 2/5] iommu/io-pgtable: Move Apple DART support to its own file Date: Thu, 22 Sep 2022 23:05:10 +0900 [thread overview] Message-ID: <ff713226-333c-72e6-da79-7f0b54b6d15d@marcan.st> (raw) In-Reply-To: <20220916094152.87137-3-j@jannau.net> 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-09-22 14:05 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-09-16 9:41 [PATCH v5 0/5] iommu: M1 Pro/Max DART support Janne Grunau 2022-09-16 9:41 ` Janne Grunau 2022-09-16 9:41 ` [PATCH v5 1/5] dt-bindings: iommu: dart: add t6000 compatible Janne Grunau 2022-09-16 9:41 ` Janne Grunau 2022-09-22 12:05 ` Hector Martin 2022-09-22 12:05 ` Hector Martin 2022-09-16 9:41 ` [PATCH v5 2/5] iommu/io-pgtable: Move Apple DART support to its own file Janne Grunau 2022-09-16 9:41 ` Janne Grunau 2022-09-22 14:05 ` Hector Martin [this message] 2022-09-22 14:05 ` Hector Martin 2022-09-16 9:41 ` [PATCH v5 3/5] iommu/io-pgtable: Add DART subpage protection support Janne Grunau 2022-09-16 9:41 ` Janne Grunau 2022-09-16 11:57 ` Rob Herring 2022-09-16 11:57 ` Rob Herring 2022-09-16 9:41 ` [PATCH v5 4/5] iommu/io-pgtable-dart: Add DART PTE support for t6000 Janne Grunau 2022-09-16 9:41 ` Janne Grunau 2022-09-16 12:03 ` Rob Herring 2022-09-16 12:03 ` Rob Herring 2022-09-16 9:41 ` [PATCH v5 5/5] iommu: dart: Support t6000 variant Janne Grunau 2022-09-16 9:41 ` Janne Grunau 2022-09-16 12:05 ` Rob Herring 2022-09-16 12:05 ` Rob Herring 2022-09-21 13:20 ` [PATCH v5 0/5] iommu: M1 Pro/Max DART support Robin Murphy 2022-09-21 13:20 ` Robin Murphy 2022-09-22 14:05 ` Hector Martin 2022-09-22 14:05 ` Hector Martin 2022-09-26 11:50 ` Joerg Roedel 2022-09-26 11:50 ` Joerg Roedel
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