[PATCH 5/6] iommu/qcom: Index contexts by asid number to allow asid 0

[Konrad Dybcio <konrad.dybcio@somainline.org>]

From: AngeloGioacchino Del Regno <angelogioacchino.delregno@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.delregno@somainline.org>
Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@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