linux-kernel - [PATCH] habanalabs: share a single ctx-mutex between all MMUs

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Date:   Sat, 14 Nov 2020 11:24:13 +0200
From:   Oded Gabbay <ogabbay@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     SW_Drivers@...ana.ai, Moti Haimovski <mhaimovski@...ana.ai>
Subject: [PATCH] habanalabs: share a single ctx-mutex between all MMUs

From: Moti Haimovski <mhaimovski@...ana.ai>

Multiple locks are usually a source of problems, which in the MMU
case can be avoided since it is relatively rare that both MMU
tables are updated at the same time.

Therefore, use a single shared lock instead of two separate ones.

Signed-off-by: Moti Haimovski <mhaimovski@...ana.ai>
Reviewed-by: Oded Gabbay <ogabbay@...nel.org>
Signed-off-by: Oded Gabbay <ogabbay@...nel.org>
---
 drivers/misc/habanalabs/common/mmu.c    | 4 ++++
 drivers/misc/habanalabs/common/mmu_v1.c | 4 ----
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/habanalabs/common/mmu.c b/drivers/misc/habanalabs/common/mmu.c
index 6f535c81478d..f4b3d02fe0d8 100644
--- a/drivers/misc/habanalabs/common/mmu.c
+++ b/drivers/misc/habanalabs/common/mmu.c
@@ -81,6 +81,8 @@ int hl_mmu_ctx_init(struct hl_ctx *ctx)
 	if (!hdev->mmu_enable)
 		return 0;
 
+	mutex_init(&ctx->mmu_lock);
+
 	if (hdev->mmu_func[MMU_DR_PGT].ctx_init != NULL) {
 		rc = hdev->mmu_func[MMU_DR_PGT].ctx_init(ctx);
 		if (rc)
@@ -115,6 +117,8 @@ void hl_mmu_ctx_fini(struct hl_ctx *ctx)
 
 	if (hdev->mmu_func[MMU_HR_PGT].ctx_fini != NULL)
 		hdev->mmu_func[MMU_HR_PGT].ctx_fini(ctx);
+
+	mutex_destroy(&ctx->mmu_lock);
 }
 
 /*
diff --git a/drivers/misc/habanalabs/common/mmu_v1.c b/drivers/misc/habanalabs/common/mmu_v1.c
index 5f62cb158eef..92b22298bb5c 100644
--- a/drivers/misc/habanalabs/common/mmu_v1.c
+++ b/drivers/misc/habanalabs/common/mmu_v1.c
@@ -481,9 +481,7 @@ static void hl_mmu_v1_fini(struct hl_device *hdev)
  */
 static int hl_mmu_v1_ctx_init(struct hl_ctx *ctx)
 {
-	mutex_init(&ctx->mmu_lock);
 	hash_init(ctx->mmu_shadow_hash);
-
 	return dram_default_mapping_init(ctx);
 }
 
@@ -516,8 +514,6 @@ static void hl_mmu_v1_ctx_fini(struct hl_ctx *ctx)
 			pgt_info->phys_addr, ctx->asid, pgt_info->num_of_ptes);
 		_free_hop(ctx, pgt_info);
 	}
-
-	mutex_destroy(&ctx->mmu_lock);
 }
 
 static int _hl_mmu_v1_unmap(struct hl_ctx *ctx,
-- 
2.17.1