[PATCH 3/7] of/iommu: add multi-map support

[Vikash Garodia <vikash.garodia@oss.qualcomm.com>]

From: Charan Teja Kalla <charan.kalla@oss.qualcomm.com>

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.

Whether multi-map is needed is reported by the callers through the
callback function passed, which is called for every input id match.

Since the requirement in the usecase[1] is for platform devices, not
sure if it is really clean to maintain this decision on the bus type at
the of_iommu layer or further to be from the respective
iommu_driver->impl_ops().

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

Signed-off-by: Charan Teja Kalla <charan.kalla@oss.qualcomm.com>
Signed-off-by: Vijayanand Jitta <vijayanand.jitta@oss.qualcomm.com>
Signed-off-by: Vikash Garodia <vikash.garodia@oss.qualcomm.com>
---
 drivers/iommu/of_iommu.c | 36 ++++++++++++++++++++++++++++--------
 drivers/of/base.c        | 38 ++++++++++++++++++++++++++++----------
 include/linux/of.h       |  6 ++++++
 3 files changed, 62 insertions(+), 18 deletions(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 768eaddf927b0700b2497b08ea21611b1a1b5688..067bb2298973671e1eaf01bb2ea52df3d2a52a44 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -16,6 +16,7 @@
 #include <linux/pci.h>
 #include <linux/slab.h>
 #include <linux/fsl/mc.h>
+#include <linux/platform_device.h>
 
 #include "iommu-priv.h"
 
@@ -41,22 +42,41 @@ static int of_iommu_xlate(struct device *dev,
 	return ret;
 }
 
+/*
+ * Callback to be called from of_map_id(), that tells if
+ * all the mappings for an input id to be maintained in
+ * parallel. Should this decission be from further layers,
+ * iommu_driver->impl_ops?
+ */
+static int of_iommu_configure_cb(struct of_map_id_arg *arg)
+{
+	struct of_phandle_args *iommu_spec = &arg->map_args;
+	struct device *dev = arg->dev;
+	int err;
+
+	err = of_iommu_xlate(dev, iommu_spec);
+	of_node_put(iommu_spec->np);
+
+	/* !iommu_spec->np may be from the bypassed translations */
+	if (!err)
+		err = (!arg->multi_map || !iommu_spec->np) ? 0 : -EAGAIN;
+
+	return err;
+}
+
 static int of_iommu_configure_dev_id(struct device_node *master_np,
 				     struct device *dev,
 				     const u32 *id)
 {
 	struct of_map_id_arg arg = {
 		.map_args = {},
+		.cb = of_iommu_configure_cb,
+		.dev = dev,
+		/* Should this be pushed to iommu_driver->impl_ops? */
+		.multi_map = dev_is_platform(dev),
 	};
-	int err;
-
-	err = of_map_iommu_id(master_np, *id, &arg);
-	if (err)
-		return err;
 
-	err = of_iommu_xlate(dev, &arg.map_args);
-	of_node_put(arg.map_args.np);
-	return err;
+	return of_map_iommu_id(master_np, *id, &arg);
 }
 
 static int of_iommu_configure_dev(struct device_node *master_np,
diff --git a/drivers/of/base.c b/drivers/of/base.c
index 606bef4f90e7d13bae4f7b0c45acd1755ad89826..a1c3c5954ec7e8eb3753c8fd782a1570f9eb9c17 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2122,14 +2122,21 @@ static bool of_check_bad_map(const __be32 *map, int len)
 	return true;
 }
 
-static int of_map_id_fill_output(struct of_map_id_arg *arg,
-				 struct device_node *phandle_node, u32 id_or_offset,
-				 const __be32 *out_base, u32 cells,
-				 bool bypass)
+/*
+ * Fill the id_out and target for the of_map_id() caller. Also
+ * call the callback passed to the of_map_id() as part of the arg
+ * that decides if to continue further search.
+ */
+static int of_map_id_fill_arg(struct of_map_id_arg *arg,
+			      struct device_node *phandle_node, u32 id_or_offset,
+			      const __be32 *out_base, u32 cells,
+			      bool bypass, bool *multi_id_map)
 {
+	int ret;
+
 	if (bypass) {
 		arg->map_args.args[0] = id_or_offset;
-		return 0;
+		goto output;
 	}
 
 	if (arg->map_args.np)
@@ -2145,7 +2152,14 @@ static int of_map_id_fill_output(struct of_map_id_arg *arg,
 
 	arg->map_args.args_count = cells;
 
-	return 0;
+output:
+	/* pass the output for the callback, callers may further decide */
+	ret =  arg->cb ? arg->cb(arg) : 0;
+
+	if (multi_id_map && ret == -EAGAIN)
+		*multi_id_map = true;
+
+	return ret;
 }
 
 /**
@@ -2179,6 +2193,7 @@ int of_map_id(const struct device_node *np, u32 id, const char *map_name,
 	int map_bytes, map_len, offset = 0;
 	bool bad_map = false;
 	const __be32 *map = NULL;
+	bool multi_id_map = false;
 
 	if (!np || !map_name || !arg)
 		return -EINVAL;
@@ -2264,23 +2279,26 @@ int of_map_id(const struct device_node *np, u32 id, const char *map_name,
 		if (masked_id < id_base || id_off >= id_len)
 			continue;
 
-		ret = of_map_id_fill_output(arg, phandle_node, id_off, out_base, cells, false);
+		ret = of_map_id_fill_arg(arg, phandle_node, id_off, out_base,
+					 cells, false, &multi_id_map);
 		if (ret == -EAGAIN)
 			continue;
 
 		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));
-		return 0;
+		return ret;
 	}
 
+	if (multi_id_map)
+		return 0;
+
 	pr_info("%pOF: no %s translation for id 0x%x on %pOF\n", np, map_name,
 		id, arg->map_args.np  ? arg->map_args.np : NULL);
 
 bypass_translation:
 	/* Bypasses translation */
-	return of_map_id_fill_output(arg, NULL, id, 0, 0, true);
-
+	return of_map_id_fill_arg(arg, NULL, id, 0, 0, true, NULL);
 err_map_len:
 	pr_err("%pOF: Error: Bad %s length: %d\n", np, map_name, map_bytes);
 	return -EINVAL;
diff --git a/include/linux/of.h b/include/linux/of.h
index 9efa6f93712c6024f05476f9fd39f3294f942ec1..abab73a76682351f5635c1127a6c899917525050 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -25,6 +25,9 @@
 typedef u32 phandle;
 typedef u32 ihandle;
 
+struct of_map_id_arg;
+typedef int (*of_map_id_cb)(struct of_map_id_arg *arg);
+
 struct property {
 	char	*name;
 	int	length;
@@ -76,6 +79,9 @@ struct of_phandle_args {
 
 struct of_map_id_arg {
 	struct of_phandle_args map_args;
+	of_map_id_cb cb;
+	struct device *dev;
+	bool multi_map;
 };
 
 struct of_phandle_iterator {

-- 
2.34.1