iommu/qcom: Index contexts by asid number to allow asid 0

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 always true: at least for MSM8956 and
MSM8976's GPU IOMMU, the gpu_user context's ASID number is zero.
To allow using a zero asid number, index the contexts by `asid`
instead of by `asid - 1`.

While at it, also enhance human readability by renaming the
`num_ctxs` member of struct qcom_iommu_dev to `max_asid`.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230622092742.74819-5-angelogioacchino.delregno@collabora.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
index a352859..60e4959 100644 (file)
--- a/drivers/iommu/arm/arm-smmu/qcom_iommu.c
+++ b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
@@ -51,8 +51,8 @@ struct qcom_iommu_dev {
        struct clk_bulk_data clks[CLK_NUM];
        void __iomem            *local_base;
        u32                      sec_id;
-       u8                       num_ctxs;
-       struct qcom_iommu_ctx   *ctxs[];   /* indexed by asid-1 */
+       u8                       max_asid;
+       struct qcom_iommu_ctx   *ctxs[];   /* indexed by asid */
 };
 
 struct qcom_iommu_ctx {
@@ -94,7 +94,7 @@ 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
@@ -534,12 +534,10 @@ 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->max_asid) ||
+           WARN_ON(qcom_iommu->ctxs[asid] == NULL)) {
                put_device(&iommu_pdev->dev);
                return -EINVAL;
        }
@@ -694,7 +692,7 @@ 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;
 }
@@ -706,7 +704,7 @@ static void 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;
 }
 
 static const struct of_device_id ctx_of_match[] = {
@@ -753,11 +751,11 @@ 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),
+       qcom_iommu = devm_kzalloc(dev, struct_size(qcom_iommu, ctxs, max_asid + 1),
                                  GFP_KERNEL);
        if (!qcom_iommu)
                return -ENOMEM;
-       qcom_iommu->num_ctxs = max_asid;
+       qcom_iommu->max_asid = max_asid;
        qcom_iommu->dev = dev;
 
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);