linux-kernel - [PATCH 1/2] iommu/riscv: Empty iommu queue before enabling it

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Message-Id: <20241213114233.12388-2-luxu.kernel@bytedance.com>
Date: Fri, 13 Dec 2024 19:42:32 +0800
From: Xu Lu <luxu.kernel@...edance.com>
To: tjeznach@...osinc.com,
	joro@...tes.org,
	will@...nel.org
Cc: lihangjing@...edance.com,
	xieyongji@...edance.com,
	guojinhui.liam@...edance.com,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Xu Lu <luxu.kernel@...edance.com>
Subject: [PATCH 1/2] iommu/riscv: Empty iommu queue before enabling it

Changing cqen/fqen/pqen from 0 to 1 sets the cqh/fqt/pqt registers to 0.
But the cqt/fqh/pqh registers are left unmodified. This commit resets
cqt/fqh/pqh registers to ensure corresponding queues are empty before
being enabled during initialization.

Signed-off-by: Xu Lu <luxu.kernel@...edance.com>
---
 drivers/iommu/riscv/iommu.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
index 8a05def774bd..84806724f568 100644
--- a/drivers/iommu/riscv/iommu.c
+++ b/drivers/iommu/riscv/iommu.c
@@ -240,6 +240,12 @@ static int riscv_iommu_queue_enable(struct riscv_iommu_device *iommu,
 		return rc;
 	}
 
+	/* Empty queue before enabling it */
+	if (queue->qid == RISCV_IOMMU_INTR_CQ)
+		riscv_iommu_writel(queue->iommu, Q_TAIL(queue), 0);
+	else
+		riscv_iommu_writel(queue->iommu, Q_HEAD(queue), 0);
+
 	/*
 	 * Enable queue with interrupts, clear any memory fault if any.
 	 * Wait for the hardware to acknowledge request and activate queue
-- 
2.20.1