linux-kernel - [PATCH 2/2] iommu: apple-dart: Allow mismatched bypass support

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Message-Id: <20250227-isp-dart-v1-2-161e91ef4f46@gmail.com>
Date: Thu, 27 Feb 2025 17:56:04 +0100
From: Sasha Finkelstein via B4 Relay <devnull+fnkl.kernel.gmail.com@...nel.org>
To: Sven Peter <sven@...npeter.dev>, Janne Grunau <j@...nau.net>, 
 Alyssa Rosenzweig <alyssa@...enzweig.io>, 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, 
 Sasha Finkelstein <fnkl.kernel@...il.com>, Hector Martin <marcan@...can.st>
Subject: [PATCH 2/2] iommu: apple-dart: Allow mismatched bypass support

From: Hector Martin <marcan@...can.st>

This is needed by ISP, which has DART0 with bypass and DART1/2 without.

Signed-off-by: Hector Martin <marcan@...can.st>
Signed-off-by: Sasha Finkelstein <fnkl.kernel@...il.com>
---
 drivers/iommu/apple-dart.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
index edb2fb22333506d7c64ad1b6321df00ebfd07747..a41ad0627be003f2b0ce42a128c3b04bb2537d56 100644
--- a/drivers/iommu/apple-dart.c
+++ b/drivers/iommu/apple-dart.c
@@ -277,6 +277,9 @@ struct apple_dart_domain {
  * @streams: streams for this device
  */
 struct apple_dart_master_cfg {
+	/* Intersection of DART capabilitles */
+	u32 supports_bypass : 1;
+
 	struct apple_dart_stream_map stream_maps[MAX_DARTS_PER_DEVICE];
 };
 
@@ -684,7 +687,7 @@ static int apple_dart_attach_dev_identity(struct iommu_domain *domain,
 	struct apple_dart_stream_map *stream_map;
 	int i;
 
-	if (!cfg->stream_maps[0].dart->supports_bypass)
+	if (!cfg->supports_bypass)
 		return -EINVAL;
 
 	for_each_stream_map(i, cfg, stream_map)
@@ -792,20 +795,25 @@ static int apple_dart_of_xlate(struct device *dev,
 		return -EINVAL;
 	sid = args->args[0];
 
-	if (!cfg)
+	if (!cfg) {
 		cfg = kzalloc(sizeof(*cfg), GFP_KERNEL);
+
+		/* Will be ANDed with DART capabilities */
+		cfg->supports_bypass = true;
+	}
 	if (!cfg)
 		return -ENOMEM;
 	dev_iommu_priv_set(dev, cfg);
 
 	cfg_dart = cfg->stream_maps[0].dart;
 	if (cfg_dart) {
-		if (cfg_dart->supports_bypass != dart->supports_bypass)
-			return -EINVAL;
 		if (cfg_dart->pgsize != dart->pgsize)
 			return -EINVAL;
 	}
 
+	if (!dart->supports_bypass)
+		cfg->supports_bypass = false;
+
 	for (i = 0; i < MAX_DARTS_PER_DEVICE; ++i) {
 		if (cfg->stream_maps[i].dart == dart) {
 			set_bit(sid, cfg->stream_maps[i].sidmap);
@@ -945,7 +953,7 @@ static int apple_dart_def_domain_type(struct device *dev)
 
 	if (cfg->stream_maps[0].dart->pgsize > PAGE_SIZE)
 		return IOMMU_DOMAIN_IDENTITY;
-	if (!cfg->stream_maps[0].dart->supports_bypass)
+	if (!cfg->supports_bypass)
 		return IOMMU_DOMAIN_DMA;
 
 	return 0;

-- 
2.48.1