linux-kernel - [PATCH 1/5] iommu/sun50i: Fix reset release

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Message-Id: <20221013181221.3247429-2-jernej.skrabec@gmail.com>
Date:   Thu, 13 Oct 2022 20:12:16 +0200
From:   Jernej Skrabec <jernej.skrabec@...il.com>
To:     maxime@...no.tech, joro@...tes.org, will@...nel.org,
        robin.murphy@....com, wens@...e.org, samuel@...lland.org
Cc:     iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Jernej Skrabec <jernej.skrabec@...il.com>
Subject: [PATCH 1/5] iommu/sun50i: Fix reset release

Reset signal is asserted by writing 0 to the corresponding locations of
masters we want to reset. So in order to deassert all reset signals, we
should write 1's to all locations.

Current code writes 1's to locations of masters which were just reset
which is good. However, at the same time it also writes 0's to other
locations and thus asserts reset signals of remaining masters. Fix code
by writing all 1's when we want to deassert all reset signals.

This bug was discovered when working with Cedrus (video decoder). When
it faulted, display went blank due to reset signal assertion.

Fixes: 4100b8c229b3 ("iommu: Add Allwinner H6 IOMMU driver")
Signed-off-by: Jernej Skrabec <jernej.skrabec@...il.com>
---
 drivers/iommu/sun50i-iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/sun50i-iommu.c b/drivers/iommu/sun50i-iommu.c
index a84c63518773..c777882d0ec2 100644
--- a/drivers/iommu/sun50i-iommu.c
+++ b/drivers/iommu/sun50i-iommu.c
@@ -27,6 +27,7 @@
 #include <linux/types.h>
 
 #define IOMMU_RESET_REG			0x010
+#define IOMMU_RESET_RELEASE_ALL			0xffffffff
 #define IOMMU_ENABLE_REG		0x020
 #define IOMMU_ENABLE_ENABLE			BIT(0)
 
@@ -893,7 +894,7 @@ static irqreturn_t sun50i_iommu_irq(int irq, void *dev_id)
 	iommu_write(iommu, IOMMU_INT_CLR_REG, status);
 
 	iommu_write(iommu, IOMMU_RESET_REG, ~status);
-	iommu_write(iommu, IOMMU_RESET_REG, status);
+	iommu_write(iommu, IOMMU_RESET_REG, IOMMU_RESET_RELEASE_ALL);
 
 	spin_unlock(&iommu->iommu_lock);
 
-- 
2.38.0