[PATCH 6.1.y 4/5] iommu/qcom: Index contexts by asid number to allow asid 0

[Sasha Levin <sashal@kernel.org>]

From: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

[ Upstream commit ec5601661bfcdc206e6ceba1b97837e763dab1ba ]

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>
Stable-dep-of: 6a3908ce56e6 ("iommu/qcom: fix device leak on of_xlate()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/arm/arm-smmu/qcom_iommu.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
index dd8d5e2f3c08..0c27de3fd2f6 100644
--- 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
@@ -559,12 +559,10 @@ 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;
 	}
@@ -722,7 +720,7 @@ 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;
 }
@@ -734,7 +732,7 @@ 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[] = {
@@ -781,11 +779,11 @@ 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);
-- 
2.51.0