Re: [PATCH 5/5] iommu/dart: Assert !locked when configuring
From: Robin Murphy <robin.murphy@arm.com>
Date: 2025-02-11 18:41:04
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On 2025-02-10 7:39 pm, Alyssa Rosenzweig wrote:
Configuration is only possible and needed for non-locked DARTs and will fail for locked DARTs. We cannot try -- assert that we do not.
Except now we absolutely will - if a locked DART and its client device are advertised to Linux, instead of gracefully refusing to touch it, we'll now attach the client to a DMA domain, firing a barrage of multiple WARNs in the process, and give it DMA ops which still cannot work. I'm not really convinced this series on its own leaves us in a better position than we're already in now... :/ How hideous is the rest of what's required to actually make this usable? Thanks, Robin.
quoted hunk ↗ jump to hunk
Signed-off-by: Alyssa Rosenzweig <redacted> --- drivers/iommu/apple-dart.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c index 29b627b38e8c37afd2b6a72865f43d24b633834a..87eb87bb2f5158d000a2c2fc801b722a2262c941 100644 --- a/drivers/iommu/apple-dart.c +++ b/drivers/iommu/apple-dart.c@@ -309,6 +309,7 @@ apple_dart_hw_enable_translation(struct apple_dart_stream_map *stream_map) struct apple_dart *dart = stream_map->dart; int sid; + WARN_ON(stream_map->dart->locked); for_each_set_bit(sid, stream_map->sidmap, dart->num_streams) writel(dart->hw->tcr_enabled, dart->regs + DART_TCR(dart, sid)); }@@ -318,6 +319,7 @@ static void apple_dart_hw_disable_dma(struct apple_dart_stream_map *stream_map) struct apple_dart *dart = stream_map->dart; int sid; + WARN_ON(stream_map->dart->locked); for_each_set_bit(sid, stream_map->sidmap, dart->num_streams) writel(dart->hw->tcr_disabled, dart->regs + DART_TCR(dart, sid)); }@@ -328,7 +330,7 @@ apple_dart_hw_enable_bypass(struct apple_dart_stream_map *stream_map) struct apple_dart *dart = stream_map->dart; int sid; - WARN_ON(!stream_map->dart->supports_bypass); + WARN_ON(stream_map->dart->locked || !stream_map->dart->supports_bypass); for_each_set_bit(sid, stream_map->sidmap, dart->num_streams) writel(dart->hw->tcr_bypass, dart->regs + DART_TCR(dart, sid));@@ -340,6 +342,7 @@ static void apple_dart_hw_set_ttbr(struct apple_dart_stream_map *stream_map, struct apple_dart *dart = stream_map->dart; int sid; + WARN_ON(stream_map->dart->locked); WARN_ON(paddr & ((1 << dart->hw->ttbr_shift) - 1)); for_each_set_bit(sid, stream_map->sidmap, dart->num_streams) writel(dart->hw->ttbr_valid |@@ -353,6 +356,7 @@ static void apple_dart_hw_clear_ttbr(struct apple_dart_stream_map *stream_map, struct apple_dart *dart = stream_map->dart; int sid; + WARN_ON(stream_map->dart->locked); for_each_set_bit(sid, stream_map->sidmap, dart->num_streams) writel(0, dart->regs + DART_TTBR(dart, sid, idx)); }