Re: [PATCH RFC 2/8] iommu/arm-smmu-v3: Add and use static helper function arm_smmu_cmdq_issue_cmd_with_sync()

[John Garry]

Obviously, inserting as many commands at a time as possible can reduce the
number of times the mutex contention participates, thereby improving the
overall performance. At least it reduces the number of calls to function
arm_smmu_cmdq_issue_cmdlist().
Therefore, function arm_smmu_cmdq_issue_cmd_with_sync() is added to insert
the 'cmd+sync' commands at a time.

Signed-off-by: Zhen Lei <thunder.leiz...@huawei.com>
---
  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 33 +++++++++++++--------
  1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c 
b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 2433d3c29b49ff2..a5361153ca1d6a4 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -858,11 +858,25 @@ static int arm_smmu_cmdq_issue_cmd(struct arm_smmu_device 
*smmu,
        return arm_smmu_cmdq_issue_cmdlist(smmu, cmd, 1, false);
  }
  
-static int arm_smmu_cmdq_issue_sync(struct arm_smmu_device *smmu)
+static int __maybe_unused arm_smmu_cmdq_issue_sync(struct arm_smmu_device 
*smmu)
  {
        return arm_smmu_cmdq_issue_cmdlist(smmu, NULL, 0, true);
  }
  
+static int arm_smmu_cmdq_issue_cmd_with_sync(struct arm_smmu_device *smmu,
+                                            struct arm_smmu_cmdq_ent *ent)
+{
+       u64 cmd[CMDQ_ENT_DWORDS];
+
+       if (arm_smmu_cmdq_build_cmd(cmd, ent)) {
+               dev_warn(smmu->dev, "ignoring unknown CMDQ opcode 0x%x\n",
+                        ent->opcode);
+               return -EINVAL;

Are any of the errors returned from the "issue command" functions 
actually consumed? I couldn't see it on mainline code from a brief browse.

+       }
+
+       return arm_smmu_cmdq_issue_cmdlist(smmu, cmd, 1, true);

Thanks,
John
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