linux-kernel - [PATCH 1/5] iommu/dart: Track if the DART is locked

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Message-Id: <20250210-locked-dart-v1-1-5d97fe247f35@rosenzweig.io>
Date: Mon, 10 Feb 2025 14:39:53 -0500
From: Alyssa Rosenzweig <alyssa@...enzweig.io>
To: Sven Peter <sven@...npeter.dev>, Janne Grunau <j@...nau.net>, 
 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, 
 Alyssa Rosenzweig <alyssa@...enzweig.io>
Subject: [PATCH 1/5] iommu/dart: Track if the DART is locked

Some DARTs are locked at boot-time. That means they are already
configured and we cannot change their configuration, which requires
special handling. Locked DARTs are identified in the configuration
register. Check this bit when probing and save the result so we can
handle accordingly.

Signed-off-by: Alyssa Rosenzweig <alyssa@...enzweig.io>
---
 drivers/iommu/apple-dart.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
index 95ba3caeb40177901086076416874b9905a1f40a..460cf96bc8001e051916f356d5d175b35e36c608 100644
--- a/drivers/iommu/apple-dart.c
+++ b/drivers/iommu/apple-dart.c
@@ -197,6 +197,7 @@ struct apple_dart_hw {
  * @lock: lock for hardware operations involving this dart
  * @pgsize: pagesize supported by this DART
  * @supports_bypass: indicates if this DART supports bypass mode
+ * @locked: indicates if this DART is locked
  * @sid2group: maps stream ids to iommu_groups
  * @iommu: iommu core device
  */
@@ -217,6 +218,7 @@ struct apple_dart {
 	u32 pgsize;
 	u32 num_streams;
 	u32 supports_bypass : 1;
+	u32 locked : 1;
 
 	struct iommu_group *sid2group[DART_MAX_STREAMS];
 	struct iommu_device iommu;
@@ -1076,6 +1078,11 @@ static irqreturn_t apple_dart_t8110_irq(int irq, void *dev)
 	return IRQ_HANDLED;
 }
 
+static bool apple_dart_is_locked(struct apple_dart *dart)
+{
+	return !!(readl(dart->regs + dart->hw->lock) & dart->hw->lock_bit);
+}
+
 static int apple_dart_probe(struct platform_device *pdev)
 {
 	int ret;
@@ -1143,6 +1150,7 @@ static int apple_dart_probe(struct platform_device *pdev)
 		goto err_clk_disable;
 	}
 
+	dart->locked = apple_dart_is_locked(dart);
 	ret = apple_dart_hw_reset(dart);
 	if (ret)
 		goto err_clk_disable;
@@ -1165,9 +1173,9 @@ 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, locked: %d] initialized\n",
 		dart->pgsize, dart->num_streams, dart->supports_bypass,
-		dart->pgsize > PAGE_SIZE);
+		dart->pgsize > PAGE_SIZE, dart->locked);
 	return 0;
 
 err_sysfs_remove:

-- 
2.48.1