linux-kernel - [PATCH v2 2/4] iommu: dart: Add flag to override bypass support

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Date:   Tue, 28 Feb 2023 21:21:30 +0100
From:   Sven Peter <sven@...npeter.dev>
To:     Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        linux-arm-kernel@...ts.infradead.org, asahi@...ts.linux.dev,
        iommu@...ts.linux.dev, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/4] iommu: dart: Add flag to override bypass support

The USB4 PCIe DARTs claim to support bypass but we never want to allow
that on externally facing ports.

Acked-by: Hector Martin <marcan@...can.st>
Signed-off-by: Sven Peter <sven@...npeter.dev>
---
 drivers/iommu/apple-dart.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
index 42666617803d..7d8b2b90cdb6 100644
--- a/drivers/iommu/apple-dart.c
+++ b/drivers/iommu/apple-dart.c
@@ -182,6 +182,8 @@ struct apple_dart_hw {
 	u64 ttbr_addr_field_shift;
 	u64 ttbr_shift;
 	int ttbr_count;
+
+	bool disable_bypass;
 };
 
 /*
@@ -1075,6 +1077,9 @@ static int apple_dart_probe(struct platform_device *pdev)
 	dart->pgsize = 1 << FIELD_GET(DART_PARAMS1_PAGE_SHIFT, dart_params[0]);
 	dart->supports_bypass = dart_params[1] & DART_PARAMS2_BYPASS_SUPPORT;
 
+	if (dart->hw->disable_bypass)
+		dart->supports_bypass = 0;
+
 	switch (dart->hw->type) {
 	case DART_T8020:
 	case DART_T6000:
-- 
2.25.1