linux-kernel - [PATCH v4 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group

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Message-Id: <20200929061325.10197-2-nicoleotsuka@gmail.com>
Date:   Mon, 28 Sep 2020 23:13:24 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     thierry.reding@...il.com, joro@...tes.org
Cc:     vdumpa@...dia.com, jonathanh@...dia.com, digetx@...il.com,
        linux-tegra@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, hch@...radead.org
Subject: [PATCH v4 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group_get

The tegra_smmu_group_get was added to group devices in different
SWGROUPs and it'd return a NULL group pointer upon a mismatch at
tegra_smmu_find_group(), so for most of clients/devices, it very
likely would mismatch and need a fallback generic_device_group().

But now tegra_smmu_group_get handles devices in same SWGROUP too,
which means that it would allocate a group for every new SWGROUP
or would directly return an existing one upon matching a SWGROUP,
i.e. any device will go through this function.

So possibility of having a NULL group pointer in device_group()
is upon failure of either devm_kzalloc() or iommu_group_alloc().
In either case, calling generic_device_group() no longer makes a
sense. Especially for devm_kzalloc() failing case, it'd cause a
problem if it fails at devm_kzalloc() yet succeeds at a fallback
generic_device_group(), because it does not create a group->list
for other devices to match.

This patch simply unwraps the function to clean it up.

Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
---

Changelog
v2->v4:
 * N/A
v1->v2:
 * Changed type of swgroup to "unsigned int", following Thierry's
   commnets.

 drivers/iommu/tegra-smmu.c | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
index 0becdbfea306..ec4c9dafff95 100644
--- a/drivers/iommu/tegra-smmu.c
+++ b/drivers/iommu/tegra-smmu.c
@@ -903,10 +903,12 @@ static void tegra_smmu_group_release(void *iommu_data)
 	mutex_unlock(&smmu->lock);
 }

-static struct iommu_group *tegra_smmu_group_get(struct tegra_smmu *smmu,
-						unsigned int swgroup)
+static struct iommu_group *tegra_smmu_device_group(struct device *dev)
 {
+	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
+	struct tegra_smmu *smmu = dev_iommu_priv_get(dev);
 	const struct tegra_smmu_group_soc *soc;
+	unsigned int swgroup = fwspec->ids[0];
 	struct tegra_smmu_group *group;
 	struct iommu_group *grp;

@@ -950,19 +952,6 @@ static struct iommu_group *tegra_smmu_group_get(struct tegra_smmu *smmu,
 	return group->group;
 }

-static struct iommu_group *tegra_smmu_device_group(struct device *dev)
-{
-	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
-	struct tegra_smmu *smmu = dev_iommu_priv_get(dev);
-	struct iommu_group *group;
-
-	group = tegra_smmu_group_get(smmu, fwspec->ids[0]);
-	if (!group)
-		group = generic_device_group(dev);
-
-	return group;
-}
-
 static int tegra_smmu_of_xlate(struct device *dev,
 			       struct of_phandle_args *args)
 {
-- 
2.17.1