[PATCH v2] of/iommu: support multiple iommu-map entries per input ID

[Vijayanand Jitta <vijayanand.jitta@xxxxxxxxxxxxxxxx>]

When multiple mappings are present for an input ID, linux matches
just the first one. There is a usecase [1] where all the mappings
are to be maintained in parallel for an iommu-map entry of a same
input id.

Add a next_offset iterator parameter to of_map_iommu_id() and
refactor of_map_id() internals into a static helper to carry it.
Update of_iommu_configure_dev_id() to loop over all matching
entries to support this case. All other callers pass NULL and
are unaffected.

[1] https://lore.kernel.org/all/20250627-video_cb-v3-0-51e18c0ffbce@xxxxxxxxxxx/

Signed-off-by: Vijayanand Jitta <vijayanand.jitta@xxxxxxxxxxxxxxxx>
---
On Qualcomm kaanapali, the VPU hardware has multiple internal blocks
that generate different stream IDs for the same input ID. The device
tree encodes them as separate iommu-map entries sharing the same input
ID:

  iommu-map = <0x100 &apps_smmu 0x1940 0x1>,
              <0x100 &apps_smmu 0x1a20 0x1>, ...

This requires multiple iommu-map entries per device.
of_iommu_configure_dev_id() currently stops at the first match,
so only one stream ID gets registered with the IOMMU.

The v1 series [1] addressed this with a callback threaded through
of_map_id().

This patch uses a next_offset iterator on of_map_iommu_id() instead,
keeping of_map_id() unchanged, and updates of_iommu_configure_dev_id()
to loop over all matching entries.

This patch also depends on iommu-cells series [4].

Changes since v1:
      - Split patches 2/7 [2] and 3/7 [3] out into this standalone series.
      - Dropped the callback (of_map_id_cb / of_map_id_arg) entirely.
      - Replaced with a next_offset iterator on of_map_iommu_id()
        only; of_map_id() public API is unchanged.
      - of_iommu_configure_dev_id() now loops explicitly; no
        bus-type heuristic (dev_is_platform()) needed.

[1] 
https://lore.kernel.org/all/20260126-kaanapali-iris-v1-0-e2646246bfc1@xxxxxxxxxxxxxxxx/
[2] 
https://lore.kernel.org/all/20260126-kaanapali-iris-v1-2-e2646246bfc1@xxxxxxxxxxxxxxxx/
[3] 
https://lore.kernel.org/all/20260126-kaanapali-iris-v1-3-e2646246bfc1@xxxxxxxxxxxxxxxx/
[4] 
https://lore.kernel.org/all/ce25b963-0e8e-4411-a406-7b466eadb1f9@xxxxxxxxxxxxxxxx/

Signed-off-by: Vijayanand Jitta <vijayanand.jitta@xxxxxxxxxxxxxxxx>
---
 drivers/iommu/of_iommu.c              | 20 +++++++----
 drivers/of/base.c                     | 65 ++++++++++++++++++++++++++++++-----
 drivers/pci/controller/dwc/pci-imx6.c |  2 +-
 drivers/pci/controller/pcie-apple.c   |  2 +-
 drivers/xen/grant-dma-ops.c           |  2 +-
 include/linux/of.h                    |  4 +--
 6 files changed, 75 insertions(+), 20 deletions(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index a18bb60f6f3d..947eedd9a88b 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -46,14 +46,22 @@ static int of_iommu_configure_dev_id(struct device_node 
*master_np,
                                     const u32 *id)
 {
        struct of_phandle_args iommu_spec = {};
-       int err;
+       int offset = 0, err;
+       bool found = false;
 
-       err = of_map_iommu_id(master_np, *id, &iommu_spec);
-       if (err)
-               return err;
+       while (!(err = of_map_iommu_id(master_np, *id, &iommu_spec, &offset))) {
+               err = of_iommu_xlate(dev, &iommu_spec);
+               of_node_put(iommu_spec.np);
+               iommu_spec.np = NULL;
+               if (err)
+                       return err;
+               found = true;
+       }
+
+       /* -ENODEV means all entries exhausted; success if at least one was 
processed */
+       if (err == -ENODEV && found)
+               return 0;
 
-       err = of_iommu_xlate(dev, &iommu_spec);
-       of_node_put(iommu_spec.np);
        return err;
 }
 
diff --git a/drivers/of/base.c b/drivers/of/base.c
index 9c44eb6d445d..71175e670757 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2146,13 +2146,13 @@ static bool of_check_bad_map(const __be32 *map, int len)
  *
  * Return: 0 on success or a standard error code on failure.
  */
-int of_map_id(const struct device_node *np, u32 id,
-              const char *map_name, const char *cells_name,
-              const char *map_mask_name,
-              struct of_phandle_args *arg)
+static int of_map_id_next(const struct device_node *np, u32 id,
+                         const char *map_name, const char *cells_name,
+                         const char *map_mask_name,
+                         struct of_phandle_args *arg, int *next_offset)
 {
        u32 map_mask, masked_id;
-       int map_bytes, map_len, offset = 0;
+       int map_bytes, map_len, offset = next_offset ? *next_offset : 0;
        bool bad_map = false;
        const __be32 *map = NULL;
 
@@ -2161,7 +2161,7 @@ int of_map_id(const struct device_node *np, u32 id,
 
        map = of_get_property(np, map_name, &map_bytes);
        if (!map) {
-               if (arg->np)
+               if (arg->np || next_offset)
                        return -ENODEV;
                /* Otherwise, no map implies no translation */
                arg->args[0] = id;
@@ -2262,9 +2262,16 @@ int of_map_id(const struct device_node *np, u32 id,
                pr_debug("%pOF: %s, using mask %08x, id-base: %08x, out-base: 
%08x, length: %08x, id: %08x -> %08x\n",
                        np, map_name, map_mask, id_base, be32_to_cpup(out_base),
                        id_len, id, id_off + be32_to_cpup(out_base));
+
+               if (next_offset)
+                       *next_offset = offset;  /* caller resumes from here */
                return 0;
        }
 
+       /* no (more) matches found in the map */
+       if (next_offset)
+               return -ENODEV;
+
        pr_info("%pOF: no %s translation for id 0x%x on %pOF\n", np, map_name,
                id, arg->np);
 
@@ -2276,6 +2283,38 @@ int of_map_id(const struct device_node *np, u32 id,
        pr_err("%pOF: Error: Bad %s length: %d\n", np, map_name, map_bytes);
        return -EINVAL;
 }
+
+/**
+ * of_map_id - Translate an ID through a downstream mapping.
+ * @np: root complex device node.
+ * @id: device ID to map.
+ * @map_name: property name of the map to use.
+ * @cells_name: property name of target specifier cells.
+ * @map_mask_name: optional property name of the mask to use.
+ * @arg: pointer to a &struct of_phandle_args. On input, @arg->np may be
+ *     set to a target device node to match, or NULL to match any. On
+ *     success, @arg->np will be set to the matched target node (with a
+ *     reference held), @arg->args_count will be set to the number of
+ *     output specifier cells as defined by @cells_name in the target node,
+ *     and @arg->args[0..args_count-1] will contain the translated output
+ *     specifier values.
+ *
+ * Given a device ID, look up the appropriate implementation-defined
+ * platform ID and/or the target device which receives transactions on that
+ * ID, as per the "iommu-map" and "msi-map" bindings. If @arg->np points to
+ * a non-NULL device node, only entries targeting that node will be matched;
+ * if it is NULL, it will receive the device node of the first matching
+ * target phandle, with a reference held.
+ *
+ * Return: 0 on success or a standard error code on failure.
+ */
+int of_map_id(const struct device_node *np, u32 id,
+             const char *map_name, const char *cells_name,
+             const char *map_mask_name,
+             struct of_phandle_args *arg)
+{
+       return of_map_id_next(np, id, map_name, cells_name, map_mask_name, arg, 
NULL);
+}
 EXPORT_SYMBOL_GPL(of_map_id);
 
 /**
@@ -2285,15 +2324,23 @@ EXPORT_SYMBOL_GPL(of_map_id);
  * @arg: pointer to a &struct of_phandle_args for the result. On success,
  *     @arg->np holds a reference to the target node that the caller must
  *     release with of_node_put().
+ * @next_offset: if non-NULL, on success it is set to the map offset just
+ *     past the matched entry. Pass this value back on the next call to
+ *     resume scanning from where the previous call left off, allowing all
+ *     matching entries for the same @id to be iterated. Pass NULL (or a
+ *     pointer to 0) to find only the first match.
  *
- * Convenience wrapper around of_map_id() using "iommu-map" and 
"iommu-map-mask".
+ * Wrapper around the internal iommu-map scanner using "iommu-map" and
+ * "iommu-map-mask". When @next_offset is non-NULL, returns -ENODEV once
+ * all matching entries have been exhausted.
  *
  * Return: 0 on success or a standard error code on failure.
  */
 int of_map_iommu_id(const struct device_node *np, u32 id,
-                   struct of_phandle_args *arg)
+                   struct of_phandle_args *arg, int *next_offset)
 {
-       return of_map_id(np, id, "iommu-map", "#iommu-cells", "iommu-map-mask", 
arg);
+       return of_map_id_next(np, id, "iommu-map", "#iommu-cells",
+                             "iommu-map-mask", arg, next_offset);
 }
 EXPORT_SYMBOL_GPL(of_map_iommu_id);
 
diff --git a/drivers/pci/controller/dwc/pci-imx6.c 
b/drivers/pci/controller/dwc/pci-imx6.c
index 5f8a11774eb5..0d7f5e6d037a 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -1146,7 +1146,7 @@ static int imx_pcie_add_lut_by_rid(struct imx_pcie 
*imx_pcie, u32 rid)
        u32 sid = 0;
 
        target = NULL;
-       err_i = of_map_iommu_id(dev->of_node, rid, &iommu_spec);
+       err_i = of_map_iommu_id(dev->of_node, rid, &iommu_spec, NULL);
        if (!err_i) {
                target = iommu_spec.np;
                sid_i = iommu_spec.args[0];
diff --git a/drivers/pci/controller/pcie-apple.c 
b/drivers/pci/controller/pcie-apple.c
index 2e86f8fd300b..c780e3f9d14d 100644
--- a/drivers/pci/controller/pcie-apple.c
+++ b/drivers/pci/controller/pcie-apple.c
@@ -765,7 +765,7 @@ static int apple_pcie_enable_device(struct pci_host_bridge 
*bridge, struct pci_d
        dev_dbg(&pdev->dev, "added to bus %s, index %d\n",
                pci_name(pdev->bus->self), port->idx);
 
-       err = of_map_iommu_id(port->pcie->dev->of_node, rid, &iommu_spec);
+       err = of_map_iommu_id(port->pcie->dev->of_node, rid, &iommu_spec, NULL);
        if (err)
                return err;
 
diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
index 36547d7cf1d6..062beb5825f5 100644
--- a/drivers/xen/grant-dma-ops.c
+++ b/drivers/xen/grant-dma-ops.c
@@ -325,7 +325,7 @@ static int xen_dt_grant_init_backend_domid(struct device 
*dev,
                struct pci_dev *pdev = to_pci_dev(dev);
                u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
 
-               if (of_map_iommu_id(np, rid, &iommu_spec)) {
+               if (of_map_iommu_id(np, rid, &iommu_spec, NULL)) {
                        dev_dbg(dev, "Cannot translate ID\n");
                        return -ESRCH;
                }
diff --git a/include/linux/of.h b/include/linux/of.h
index 953f2dbe0e86..990849f00e74 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -467,7 +467,7 @@ int of_map_id(const struct device_node *np, u32 id,
               struct of_phandle_args *arg);
 
 int of_map_iommu_id(const struct device_node *np, u32 id,
-                   struct of_phandle_args *arg);
+                   struct of_phandle_args *arg, int *next_offset);
 
 int of_map_msi_id(const struct device_node *np, u32 id,
                  struct of_phandle_args *arg);
@@ -943,7 +943,7 @@ static inline int of_map_id(const struct device_node *np, 
u32 id,
 }
 
 static inline int of_map_iommu_id(const struct device_node *np, u32 id,
-                                 struct of_phandle_args *arg)
+                                 struct of_phandle_args *arg, int *next_offset)
 {
        return -EINVAL;
 }

---
base-commit: 9e94742cffb7541f55fa904a40c1ca9d836d303d
change-id: 20260315-iommu_multi_map-8c9b78490ace

Best regards,
-- 
Vijayanand Jitta <vijayanand.jitta@xxxxxxxxxxxxxxxx>