From: AngeloGioacchino Del Regno <angelogioacchino.delre...@somainline.org>

This driver was indexing the contexts by asid-1, which is probably
done under the assumption that the first ASID is always 1.

Unfortunately this is not entirely true: at least in the MSM8956
and MSM8976 GPU IOMMU, the gpu_user context's ASID number is zero.
To allow using an asid number of zero, stop indexing the contexts
by asid-1 and rather index them by asid.

Signed-off-by: AngeloGioacchino Del Regno 
<angelogioacchino.delre...@somainline.org>
Signed-off-by: Marijn Suijten <marijn.suij...@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dyb...@somainline.org>
---
 drivers/iommu/arm/arm-smmu/qcom_iommu.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c 
b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
index 530aa92bf6a1..4fefbab15b71 100644
--- a/drivers/iommu/arm/arm-smmu/qcom_iommu.c
+++ b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
@@ -53,7 +53,7 @@ struct qcom_iommu_dev {
        u32                      sec_id;
        u8                       num_ctxs;
        bool                     use_aarch64_pt;
-       struct qcom_iommu_ctx   *ctxs[];   /* indexed by asid-1 */
+       struct qcom_iommu_ctx   *ctxs[];   /* indexed by asid */
 };
 
 struct qcom_iommu_ctx {
@@ -95,7 +95,7 @@ static struct qcom_iommu_ctx * to_ctx(struct 
qcom_iommu_domain *d, unsigned asid
        struct qcom_iommu_dev *qcom_iommu = d->iommu;
        if (!qcom_iommu)
                return NULL;
-       return qcom_iommu->ctxs[asid - 1];
+       return qcom_iommu->ctxs[asid];
 }
 
 static inline void
@@ -614,12 +614,10 @@ static int qcom_iommu_of_xlate(struct device *dev, struct 
of_phandle_args *args)
        qcom_iommu = platform_get_drvdata(iommu_pdev);
 
        /* make sure the asid specified in dt is valid, so we don't have
-        * to sanity check this elsewhere, since 'asid - 1' is used to
-        * index into qcom_iommu->ctxs:
+        * to sanity check this elsewhere:
         */
-       if (WARN_ON(asid < 1) ||
-           WARN_ON(asid > qcom_iommu->num_ctxs) ||
-           WARN_ON(qcom_iommu->ctxs[asid - 1] == NULL)) {
+       if (WARN_ON(asid >= qcom_iommu->num_ctxs) ||
+           WARN_ON(qcom_iommu->ctxs[asid] == NULL)) {
                put_device(&iommu_pdev->dev);
                return -EINVAL;
        }
@@ -778,7 +776,7 @@ static int qcom_iommu_ctx_probe(struct platform_device 
*pdev)
 
        dev_dbg(dev, "found asid %u\n", ctx->asid);
 
-       qcom_iommu->ctxs[ctx->asid - 1] = ctx;
+       qcom_iommu->ctxs[ctx->asid] = ctx;
 
        return 0;
 }
@@ -790,7 +788,7 @@ static int qcom_iommu_ctx_remove(struct platform_device 
*pdev)
 
        platform_set_drvdata(pdev, NULL);
 
-       qcom_iommu->ctxs[ctx->asid - 1] = NULL;
+       qcom_iommu->ctxs[ctx->asid] = NULL;
 
        return 0;
 }
@@ -828,7 +826,7 @@ static int qcom_iommu_device_probe(struct platform_device 
*pdev)
        struct device *dev = &pdev->dev;
        struct resource *res;
        struct clk *clk;
-       int ret, max_asid = 0;
+       int ret, num_ctxs, max_asid = 0;
 
        /* find the max asid (which is 1:1 to ctx bank idx), so we know how
         * many child ctx devices we have:
@@ -836,11 +834,13 @@ static int qcom_iommu_device_probe(struct platform_device 
*pdev)
        for_each_child_of_node(dev->of_node, child)
                max_asid = max(max_asid, get_asid(child));
 
-       qcom_iommu = devm_kzalloc(dev, struct_size(qcom_iommu, ctxs, max_asid),
+       num_ctxs = max_asid + 1;
+
+       qcom_iommu = devm_kzalloc(dev, struct_size(qcom_iommu, ctxs, num_ctxs),
                                  GFP_KERNEL);
        if (!qcom_iommu)
                return -ENOMEM;
-       qcom_iommu->num_ctxs = max_asid;
+       qcom_iommu->num_ctxs = num_ctxs;
        qcom_iommu->dev = dev;
 
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-- 
2.36.1

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