linux-kernel - [PATCH] iommu/dart: Initialize DART_STREAMS

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Date:   Tue, 19 Oct 2021 18:22:53 +0200
From:   Sven Peter <sven@...npeter.dev>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Sven Peter <sven@...npeter.dev>,
        Martin Povišer <povik@...tonmail.com>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Hector Martin <marcan@...can.st>,
        Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iommu/dart: Initialize DART_STREAMS_ENABLE

DART has an additional global register to control which streams are
isolated. This register is a bit redundant since DART_TCR can already
be used to control isolation and is usually initialized to DART_STREAM_ALL
by the time we get control. Some DARTs (namely the one used for the audio
controller) however have some streams disabled initially. Make sure those
work by initializing DART_STREAMS_ENABLE during reset.

Reported-by: Martin Povišer <povik@...tonmail.com>
Signed-off-by: Sven Peter <sven@...npeter.dev>
---

While this could technically count as a fix I don't think it needs to go to
5.15 since no driver that requires this is in there. The first driver
that needs this will likely only be ready for the 5.17 merge window.

 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 ce92195db638..6f8c240d8d40 100644
--- a/drivers/iommu/apple-dart.c
+++ b/drivers/iommu/apple-dart.c
@@ -70,6 +70,8 @@
 #define DART_ERROR_ADDR_HI 0x54
 #define DART_ERROR_ADDR_LO 0x50
 
+#define DART_STREAMS_ENABLE 0xfc
+
 #define DART_TCR(sid) (0x100 + 4 * (sid))
 #define DART_TCR_TRANSLATE_ENABLE BIT(7)
 #define DART_TCR_BYPASS0_ENABLE BIT(8)
@@ -299,6 +301,9 @@ static int apple_dart_hw_reset(struct apple_dart *dart)
 	apple_dart_hw_disable_dma(&stream_map);
 	apple_dart_hw_clear_all_ttbrs(&stream_map);
 
+	/* enable all streams globally since TCR is used to control isolation */
+	writel(DART_STREAM_ALL, dart->regs + DART_STREAMS_ENABLE);
+
 	/* clear any pending errors before the interrupt is unmasked */
 	writel(readl(dart->regs + DART_ERROR), dart->regs + DART_ERROR);
 
-- 
2.25.1