[PATCH v2 3/3] of: Respect #{iommu,msi}-cells in maps

[Vijayanand Jitta <vijayanand.jitta@oss.qualcomm.com>]

From: Robin Murphy <robin.murphy@arm.com>

So far our parsing of {iommu,msi}-map properites has always blindly
asusmed that the output specifiers will always have exactly 1 cell.
This typically does happen to be the case, but is not actually enforced
(and the PCI msi-map binding even explicitly states support for 0 or 1
cells) - as a result we've now ended up with dodgy DTs out in the field
which depend on this behaviour to map a 1-cell specifier for a 2-cell
provider, despite that being bogus per the bindings themselves.

Since there is some potential use in being able to map at least single
input IDs to multi-cell output specifiers (and properly support 0-cell
outputs as well), add support for properly parsing and using the target
nodes' #cells values, albeit with the unfortunate complication of still
having to work around expectations of the old behaviour too.

Since there are multi-cell output specifiers, the callers of of_map_id()
may need to get the exact cell output value for further processing.
Added support for that part --charan

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Vijayanand Jitta <vijayanand.jitta@oss.qualcomm.com>
---
 drivers/iommu/of_iommu.c |   3 +-
 drivers/of/base.c        | 107 ++++++++++++++++++++++++++++++---------
 include/linux/of.h       |  17 ++++---
 3 files changed, 94 insertions(+), 33 deletions(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index eac62bc441c5..48759cf1d900 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -45,10 +45,11 @@ static int of_iommu_configure_dev_id(struct device_node *master_np,
 				     struct device *dev,
 				     const u32 *id)
 {
-	struct of_phandle_args iommu_spec = { .args_count = 1 };
+	struct of_phandle_args iommu_spec = {};
 	struct of_map_id_arg arg = {
 		.target = &iommu_spec.np,
 		.id_out = iommu_spec.args,
+		.map_cells = &iommu_spec.args_count,
 	};
 	int err;
 
diff --git a/drivers/of/base.c b/drivers/of/base.c
index b8f78a9e6a09..68a7d6ddba66 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2045,11 +2045,30 @@ int of_find_last_cache_level(unsigned int cpu)
 	return cache_level;
 }
 
+/*
+ * Some DTs have an iommu-map targeting a 2-cell IOMMU node while
+ * specifying only 1 cell. Fortunately they all consist of length == 1
+ * entries with the same target, so check for that pattern.
+ */
+static bool of_check_bad_map(const __be32 *map, int len)
+{
+	__be32 phandle = map[1];
+
+	if (len % 4)
+		return false;
+	for (int i = 0; i < len; i += 4) {
+		if (map[i + 1] != phandle || map[i + 3] != cpu_to_be32(1))
+			return false;
+	}
+	return true;
+}
+
 /**
  * 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: contains the optional params, @target which is a pointer
  *	to the target device node and id_out which is a pointer
@@ -2065,18 +2084,19 @@ int of_find_last_cache_level(unsigned int cpu)
  *
  * 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 *map_mask_name,
-	       struct of_map_id_arg *arg)
+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_map_id_arg *arg)
 {
 	u32 map_mask, masked_id;
-	int map_len;
+	int map_bytes, map_len, offset = 0;
+	bool bad_map = false;
 	const __be32 *map = NULL;
 
 	if (!np || !map_name || !arg || (!arg->target && !arg->id_out))
 		return -EINVAL;
 
-	map = of_get_property(np, map_name, &map_len);
+	map = of_get_property(np, map_name, &map_bytes);
 	if (!map) {
 		if (arg->target)
 			return -ENODEV;
@@ -2085,11 +2105,9 @@ int of_map_id(const struct device_node *np, u32 id,
 		return 0;
 	}
 
-	if (!map_len || map_len % (4 * sizeof(*map))) {
-		pr_err("%pOF: Error: Bad %s length: %d\n", np,
-			map_name, map_len);
-		return -EINVAL;
-	}
+	if (map_bytes % sizeof(*map))
+		goto err_map_len;
+	map_len = map_bytes / sizeof(*map);
 
 	/* The default is to select all bits. */
 	map_mask = 0xffffffff;
@@ -2102,27 +2120,62 @@ int of_map_id(const struct device_node *np, u32 id,
 		of_property_read_u32(np, map_mask_name, &map_mask);
 
 	masked_id = map_mask & id;
-	for ( ; map_len > 0; map_len -= 4 * sizeof(*map), map += 4) {
+	while (offset < map_len) {
 		struct device_node *phandle_node;
-		u32 id_base = be32_to_cpup(map + 0);
-		u32 phandle = be32_to_cpup(map + 1);
-		u32 out_base = be32_to_cpup(map + 2);
-		u32 id_len = be32_to_cpup(map + 3);
+		u32 id_base, phandle, cells, id_len, id_off;
+		const __be32 *out_base;
+
+		if (map_len - offset < 2)
+			goto err_map_len;
 
+		id_base = be32_to_cpup(map + offset);
 		if (id_base & ~map_mask) {
-			pr_err("%pOF: Invalid %s translation - %s-mask (0x%x) ignores id-base (0x%x)\n",
-				np, map_name, map_name,
+			pr_err("%pOF: Invalid %s translation - %s (0x%x) ignores id-base (0x%x)\n",
+				np, map_name, map_mask_name,
 				map_mask, id_base);
 			return -EFAULT;
 		}
 
-		if (masked_id < id_base || masked_id >= id_base + id_len)
-			continue;
-
+		phandle = be32_to_cpup(map + offset + 1);
 		phandle_node = of_find_node_by_phandle(phandle);
 		if (!phandle_node)
 			return -ENODEV;
 
+		if (!bad_map && of_property_read_u32(phandle_node, cells_name, &cells)) {
+			pr_err("%pOF: missing %s property\n", phandle_node, cells_name);
+			return -EINVAL;
+		}
+
+		if (map_len - offset < 3 + cells)
+			goto err_map_len;
+
+		if (offset == 0 && cells == 2) {
+			bad_map = of_check_bad_map(map, map_len);
+			if (bad_map) {
+				pr_warn_once("%pOF: %s mismatches target %s, assuming extra cell of 0\n",
+				np, map_name, cells_name);
+				cells = 1;
+			}
+		}
+
+		out_base = map + offset + 2;
+		offset += 3 + cells;
+
+		id_len = be32_to_cpup(map + offset - 1);
+		if (id_len > 1 && cells > 1) {
+			/*
+			 * With 1 output cell we reasonably assume its value
+			 * has a linear relationship to the input; with more,
+			 * we'd need help from the provider to know what to do.
+			 */
+			pr_err("%pOF: Unsupported %s - cannot handle %d-ID range with %d-cell output specifier\n",
+				np, map_name, id_len, cells);
+			return -EINVAL;
+		}
+		id_off = masked_id - id_base;
+		if (masked_id < id_base || id_off >= id_len)
+			continue;
+
 		if (arg->target) {
 			if (*arg->target)
 				of_node_put(phandle_node);
@@ -2133,12 +2186,14 @@ int of_map_id(const struct device_node *np, u32 id,
 				continue;
 		}
 
-		if (arg->id_out)
-			*arg->id_out = masked_id - id_base + out_base;
+		for (int i = 0; arg->id_out && i < cells; i++)
+			arg->id_out[i] = id_off + be32_to_cpu(out_base[i]);
 
+		if (arg->map_cells)
+			*arg->map_cells = cells;
 		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, out_base,
-			id_len, id, masked_id - id_base + out_base);
+			np, map_name, map_mask, id_base, be32_to_cpup(out_base),
+			id_len, id, id_off + be32_to_cpup(out_base));
 		return 0;
 	}
 
@@ -2149,5 +2204,9 @@ int of_map_id(const struct device_node *np, u32 id,
 	if (arg->id_out)
 		*arg->id_out = id;
 	return 0;
+
+err_map_len:
+	pr_err("%pOF: Error: Bad %s length: %d\n", np, map_name, map_bytes);
+	return -EINVAL;
 }
 EXPORT_SYMBOL_GPL(of_map_id);
diff --git a/include/linux/of.h b/include/linux/of.h
index 21bdce2b37ca..1981509c7918 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -29,6 +29,7 @@ struct device_node;
 struct of_map_id_arg {
 	struct device_node **target;
 	u32 *id_out;
+	u32 *map_cells;
 };
 
 struct property {
@@ -462,9 +463,9 @@ const char *of_prop_next_string(const struct property *prop, const char *cur);
 
 bool of_console_check(const struct device_node *dn, char *name, int index);
 
-int of_map_id(const struct device_node *np, u32 id,
-	       const char *map_name, const char *map_mask_name,
-	       struct of_map_id_arg *arg);
+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_map_id_arg *arg);
 
 phys_addr_t of_dma_get_max_cpu_address(struct device_node *np);
 
@@ -911,9 +912,9 @@ static inline void of_property_clear_flag(struct property *p, unsigned long flag
 {
 }
 
-static inline int of_map_id(const struct device_node *np, u32 id,
-			     const char *map_name, const char *map_mask_name,
-			     struct of_map_id_arg *arg)
+static inline 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_map_id_arg *arg);
 {
 	return -EINVAL;
 }
@@ -1444,7 +1445,7 @@ static inline int of_property_read_s32(const struct device_node *np,
 static inline int of_map_iommu_id(const struct device_node *np, u32 id,
 				  struct of_map_id_arg *arg)
 {
-	return of_map_id(np, id, "iommu-map", "iommu-map-mask", arg);
+	return of_map_id(np, id, "iommu-map", "#iommu-cells", "iommu-map-mask", arg);
 }
 
 static inline int of_map_msi_id(const struct device_node *np, u32 id,
@@ -1455,7 +1456,7 @@ static inline int of_map_msi_id(const struct device_node *np, u32 id,
 		.id_out = id_out,
 	};
 
-	return of_map_id(np, id, "msi-map", "msi-map-mask", &arg);
+	return of_map_id(np, id, "msi-map", "#msi-cells", "msi-map-mask", &arg);
 }
 
 #define of_for_each_phandle(it, err, np, ln, cn, cc)			\
-- 
2.34.1