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

[kholk11@xxxxxxxxx]

From: AngeloGioacchino Del Regno <kholk11@xxxxxxxxx>

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 <kholk11@xxxxxxxxx>
---
 drivers/iommu/qcom_iommu.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c
index 233ef496af27..03c68fe9439b 100644
--- a/drivers/iommu/qcom_iommu.c
+++ b/drivers/iommu/qcom_iommu.c
@@ -49,7 +49,7 @@ struct qcom_iommu_dev {
 	u32			 sec_id;
 	u8			 num_ctxs;
 	bool			 use_aarch64_pt;
-	struct qcom_iommu_ctx	*ctxs[0];   /* indexed by asid-1 */
+	struct qcom_iommu_ctx	*ctxs[0];   /* indexed by asid */
 };
 
 struct qcom_iommu_ctx {
@@ -87,7 +87,7 @@ static struct qcom_iommu_ctx * to_ctx(struct iommu_fwspec *fwspec, unsigned asid
 	struct qcom_iommu_dev *qcom_iommu = to_iommu(fwspec);
 	if (!qcom_iommu)
 		return NULL;
-	return qcom_iommu->ctxs[asid - 1];
+	return qcom_iommu->ctxs[asid];
 }
 
 static inline void
@@ -604,12 +604,10 @@ 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))
 		return -EINVAL;
 
 	if (!fwspec->iommu_priv) {
@@ -789,7 +787,7 @@ 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;
 }
@@ -801,7 +799,7 @@ 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;
 }
@@ -846,7 +844,8 @@ 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));
 
-	sz = sizeof(*qcom_iommu) + (max_asid * sizeof(qcom_iommu->ctxs[0]));
+	sz = sizeof(*qcom_iommu);
+	sz += (max_asid + 1) * sizeof(qcom_iommu->ctxs[0]);
 
 	qcom_iommu = devm_kzalloc(dev, sz, GFP_KERNEL);
 	if (!qcom_iommu)
-- 
2.21.0