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Message-ID: <c9440d31-add4-4c0f-ac2a-184e771ab455@kernel.org>
Date: Sat, 16 Aug 2025 15:50:06 +0200
From: Sven Peter <sven@...nel.org>
To: Janne Grunau <j@...nau.net>, Alyssa Rosenzweig <alyssa@...enzweig.io>,
Neal Gompa <neal@...pa.dev>, Joerg Roedel <joro@...tes.org>,
Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>
Cc: asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
Hector Martin <marcan@...can.st>
Subject: Re: [PATCH 3/3] iommu: apple-dart: Add 4-level page table support
On 14.08.25 10:40, Janne Grunau wrote:
> From: Hector Martin <marcan@...can.st>
>
> The T8110 variant DART implementation on T602x SoCs indicates an IAS of
> 42, which requires an extra page table level. The extra level is
> optional, but let's implement it.
>
> Since the driver failed at IO page table creation with 42-bit IAS add
> "apple,t6020-dart" as separate compatible using the T8110 HW data.
Is the commit description outdated? I don't see this change anywhere.
>
> Later it might be useful to restrict this based on the actual attached
> devices, since most won't need that much address space anyway.
>
> Signed-off-by: Hector Martin <marcan@...can.st>
> Signed-off-by: Janne Grunau <j@...nau.net>
> ---
> drivers/iommu/apple-dart.c | 23 +++++++++++++++++------
> 1 file changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
> index e72a93e78e26ca61b233c83d439dbdfadf040fc6..bb48e8603d6c84bcf107294d851c2f2fc1273298 100644
> --- a/drivers/iommu/apple-dart.c
> +++ b/drivers/iommu/apple-dart.c
> @@ -133,6 +133,7 @@
> #define DART_T8110_TCR 0x1000
> #define DART_T8110_TCR_REMAP GENMASK(11, 8)
> #define DART_T8110_TCR_REMAP_EN BIT(7)
> +#define DART_T8110_TCR_FOUR_LEVEL BIT(3)
> #define DART_T8110_TCR_BYPASS_DAPF BIT(2)
> #define DART_T8110_TCR_BYPASS_DART BIT(1)
> #define DART_T8110_TCR_TRANSLATE_ENABLE BIT(0)
> @@ -177,6 +178,7 @@ struct apple_dart_hw {
> u32 tcr_enabled;
> u32 tcr_disabled;
> u32 tcr_bypass;
> + u32 tcr_4level;
>
> u32 ttbr;
> u32 ttbr_valid;
> @@ -217,6 +219,7 @@ struct apple_dart {
> u32 pgsize;
> u32 num_streams;
> u32 supports_bypass : 1;
> + u32 four_level : 1;
>
> struct iommu_group *sid2group[DART_MAX_STREAMS];
> struct iommu_device iommu;
> @@ -305,13 +308,16 @@ static struct apple_dart_domain *to_dart_domain(struct iommu_domain *dom)
> }
>
> static void
> -apple_dart_hw_enable_translation(struct apple_dart_stream_map *stream_map)
> +apple_dart_hw_enable_translation(struct apple_dart_stream_map *stream_map, int levels)
> {
> struct apple_dart *dart = stream_map->dart;
> int sid;
>
> + WARN_ON(levels != 3 && levels != 4);
> + WARN_ON(levels == 4 && !dart->four_level);
> for_each_set_bit(sid, stream_map->sidmap, dart->num_streams)
> - writel(dart->hw->tcr_enabled, dart->regs + DART_TCR(dart, sid));
> + writel(dart->hw->tcr_enabled | (levels == 4 ? dart->hw->tcr_4level : 0),
> + dart->regs + DART_TCR(dart, sid));
This is a bit hard to read, I'd prefer an explicit
if (dart->hw->tcr_4level) here.
> }
>
> static void apple_dart_hw_disable_dma(struct apple_dart_stream_map *stream_map)
> @@ -569,7 +575,8 @@ apple_dart_setup_translation(struct apple_dart_domain *domain,
> for (; i < stream_map->dart->hw->ttbr_count; ++i)
> apple_dart_hw_clear_ttbr(stream_map, i);
>
> - apple_dart_hw_enable_translation(stream_map);
> + apple_dart_hw_enable_translation(stream_map,
> + pgtbl_cfg->apple_dart_cfg.n_levels);
> stream_map->dart->hw->invalidate_tlb(stream_map);
> }
>
> @@ -614,7 +621,7 @@ static int apple_dart_finalize_domain(struct apple_dart_domain *dart_domain,
> dart_domain->domain.pgsize_bitmap = pgtbl_cfg.pgsize_bitmap;
> dart_domain->domain.geometry.aperture_start = 0;
> dart_domain->domain.geometry.aperture_end =
> - (dma_addr_t)DMA_BIT_MASK(dart->ias);
> + (dma_addr_t)DMA_BIT_MASK(pgtbl_cfg.ias);
> dart_domain->domain.geometry.force_aperture = true;
>
> dart_domain->finalized = true;
> @@ -807,6 +814,8 @@ static int apple_dart_of_xlate(struct device *dev,
> if (cfg_dart) {
> if (cfg_dart->pgsize != dart->pgsize)
> return -EINVAL;
> + if (cfg_dart->ias != dart->ias)
> + return -EINVAL;
> }
>
> cfg->supports_bypass &= dart->supports_bypass;
> @@ -1137,6 +1146,7 @@ static int apple_dart_probe(struct platform_device *pdev)
> dart->ias = FIELD_GET(DART_T8110_PARAMS3_VA_WIDTH, dart_params[2]);
> dart->oas = FIELD_GET(DART_T8110_PARAMS3_PA_WIDTH, dart_params[2]);
> dart->num_streams = FIELD_GET(DART_T8110_PARAMS4_NUM_SIDS, dart_params[3]);
> + dart->four_level = dart->ias > 36;
> break;
> }
>
> @@ -1169,9 +1179,9 @@ static int apple_dart_probe(struct platform_device *pdev)
>
> dev_info(
> &pdev->dev,
> - "DART [pagesize %x, %d streams, bypass support: %d, bypass forced: %d] initialized\n",
> + "DART [pagesize %x, %d streams, bypass support: %d, bypass forced: %d, AS %d -> %d] initialized\n",
> dart->pgsize, dart->num_streams, dart->supports_bypass,
> - dart->pgsize > PAGE_SIZE);
> + dart->pgsize > PAGE_SIZE, dart->ias, dart->oas);
> return 0;
>
> err_sysfs_remove:
> @@ -1292,6 +1302,7 @@ static const struct apple_dart_hw apple_dart_hw_t8110 = {
> .tcr_enabled = DART_T8110_TCR_TRANSLATE_ENABLE,
> .tcr_disabled = 0,
> .tcr_bypass = DART_T8110_TCR_BYPASS_DAPF | DART_T8110_TCR_BYPASS_DART,
> + .tcr_4level = DART_T8110_TCR_FOUR_LEVEL,
>
> .ttbr = DART_T8110_TTBR,
> .ttbr_valid = DART_T8110_TTBR_VALID,
>
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