[PATCH 1/6] iommu/qcom: Use the asid read from device-tree if specified

[kholk11@gmail.com]

From: AngeloGioacchino Del Regno <kholk11@gmail.com>

As specified in this driver, the context banks are 0x1000 apart.
Problem is that sometimes the context number (our asid) does not
match this logic and we end up using the wrong one: this starts
being a problem in the case that we need to send TZ commands
to do anything on a specific context.

For this reason, read the ASID from the DT if the property
"qcom,ctx-num" is present on the IOMMU context node.

Signed-off-by: AngeloGioacchino Del Regno <kholk11@gmail.com>
---
 .../devicetree/bindings/iommu/qcom,iommu.txt    |  1 +
 drivers/iommu/qcom_iommu.c                      | 17 ++++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/iommu/qcom,iommu.txt b/Documentation/devicetree/bindings/iommu/qcom,iommu.txt
index 059139abce35..98102b323196 100644
--- a/Documentation/devicetree/bindings/iommu/qcom,iommu.txt
+++ b/Documentation/devicetree/bindings/iommu/qcom,iommu.txt
@@ -38,6 +38,7 @@ to non-secure vs secure interrupt line.
         - "qcom,msm-iommu-v1-sec" : secure context bank
   - reg            : Base address and size of context bank within the iommu
   - interrupts     : The context fault irq.
+  - qcom,ctx-num   : The number associated to the context bank
 
 ** Optional properties:
 
diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c
index dadc707573a2..5837556af147 100644
--- a/drivers/iommu/qcom_iommu.c
+++ b/drivers/iommu/qcom_iommu.c
@@ -557,7 +557,8 @@ static int qcom_iommu_of_xlate(struct device *dev, struct of_phandle_args *args)
 	 * index into qcom_iommu->ctxs:
 	 */
 	if (WARN_ON(asid < 1) ||
-	    WARN_ON(asid > qcom_iommu->num_ctxs))
+	    WARN_ON(asid > qcom_iommu->num_ctxs) ||
+	    WARN_ON(qcom_iommu->ctxs[asid - 1] == NULL))
 		return -EINVAL;
 
 	if (!fwspec->iommu_priv) {
@@ -665,7 +666,8 @@ static int qcom_iommu_sec_ptbl_init(struct device *dev)
 
 static int get_asid(const struct device_node *np)
 {
-	u32 reg;
+	u32 reg, val;
+	int asid;
 
 	/* read the "reg" property directly to get the relative address
 	 * of the context bank, and calculate the asid from that:
@@ -673,7 +675,16 @@ static int get_asid(const struct device_node *np)
 	if (of_property_read_u32_index(np, "reg", 0, &reg))
 		return -ENODEV;
 
-	return reg / 0x1000;      /* context banks are 0x1000 apart */
+	/* Context banks are 0x1000 apart but, in some cases, the ASID
+	 * number doesn't match to this logic and needs to be passed
+	 * from the DT configuration explicitly.
+	 */
+	if (of_property_read_u32(np, "qcom,ctx-num", &val))
+		asid = reg / 0x1000;
+	else
+		asid = val;
+
+	return asid;
 }
 
 static int qcom_iommu_ctx_probe(struct platform_device *pdev)
-- 
2.21.0

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