[PATCH v13 3/3] of: Respect #{iommu,msi}-cells in maps

[Vijayanand Jitta <vijayanand.jitta@xxxxxxxxxxxxxxxx>]

From: Robin Murphy <robin.murphy@xxxxxxx>

So far our parsing of {iommu,msi}-map properties has always blindly
assumed 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.
Update of_map_id() to set args_count in the output to reflect the actual
number of output specifier cells.

Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Charan Teja Kalla <charan.kalla@xxxxxxxxxxxxxxxx>
Signed-off-by: Vijayanand Jitta <vijayanand.jitta@xxxxxxxxxxxxxxxx>
---
 drivers/of/base.c  | 157 +++++++++++++++++++++++++++++++++++++++++------------
 include/linux/of.h |   6 +-
 2 files changed, 125 insertions(+), 38 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index b3d002015192..2554e4f1a181 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2096,18 +2096,48 @@ 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 value '1'
+ * as the 2nd cell entry with the same target, so check for that pattern.
+ *
+ * Example:
+ *     IOMMU node:
+ *             #iommu-cells = <2>;
+ *
+ *     Device node:
+ *             iommu-map = <0x0000 &smmu 0x0000 0x1>,
+ *                         <0x0100 &smmu 0x0100 0x1>;
+ */
+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.
  * @filter_np: optional device node to filter matches by, or NULL to match any.
  *     If non-NULL, only map entries targeting this node will be matched.
  * @arg: pointer to a &struct of_phandle_args for the result. On success,
- *     @arg->args[0] will contain the translated ID. If a map entry was
- *     matched, @arg->np will be set to the target node with a reference
- *     held that the caller must release with of_node_put().
+ *     @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. If a map entry was matched, @arg->np will be set
+ *     to the target node with a reference held that the caller must release
+ *     with of_node_put().
  *
  * Given a device ID, look up the appropriate implementation-defined
  * platform ID and/or the target device which receives transactions on that
@@ -2116,17 +2146,19 @@ 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,
+              const char *map_name, const char *cells_name,
+              const char *map_mask_name,
               const struct device_node *filter_np, struct of_phandle_args *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)
                return -EINVAL;
 
-       map = of_get_property(np, map_name, &map_len);
+       map = of_get_property(np, map_name, &map_bytes);
        if (!map) {
                if (filter_np)
                        return -ENODEV;
@@ -2136,11 +2168,9 @@ 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;
@@ -2153,39 +2183,84 @@ 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, id_len, id_off, cells = 0;
+               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,
-                               map_mask, id_base);
+                       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) {
+                       cells = 1;
+               } else if (of_property_read_u32(phandle_node, cells_name, 
&cells)) {
+                       pr_err("%pOF: missing %s property\n", phandle_node, 
cells_name);
+                       of_node_put(phandle_node);
+                       return -EINVAL;
+               }
+
+               if (map_len - offset < 3 + cells) {
+                       of_node_put(phandle_node);
+                       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);
+                       of_node_put(phandle_node);
+                       return -EINVAL;
+               }
+               id_off = masked_id - id_base;
+               if (masked_id < id_base || id_off >= id_len) {
+                       of_node_put(phandle_node);
+                       continue;
+               }
+
                if (filter_np && filter_np != phandle_node) {
                        of_node_put(phandle_node);
                        continue;
                }
 
                arg->np = phandle_node;
-               arg->args[0] = masked_id - id_base + out_base;
-               arg->args_count = 1;
+               for (int i = 0; i < cells; i++)
+                       arg->args[i] = id_off + be32_to_cpu(out_base[i]);
+               arg->args_count = 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;
        }
 
@@ -2196,6 +2271,10 @@ int of_map_id(const struct device_node *np, u32 id,
        arg->args[0] = id;
        arg->args_count = 1;
        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);
 
@@ -2205,18 +2284,21 @@ EXPORT_SYMBOL_GPL(of_map_id);
  * @id: Requester ID of the device (e.g. PCI RID/BDF or a platform
  *      stream/device ID) used as the lookup key in the iommu-map table.
  * @arg: pointer to a &struct of_phandle_args for the result. On success,
- *     @arg->args[0] contains the translated ID. If a map entry was matched,
- *     @arg->np holds a reference to the target node that the caller must
- *     release with of_node_put().
+ *     @arg->args_count will be set to the number of output specifier cells
+ *     and @arg->args[0..args_count-1] will contain the translated output
+ *     specifier values. If a map entry was matched, @arg->np holds a
+ *     reference to the target node that the caller must release with
+ *     of_node_put().
  *
- * Convenience wrapper around of_map_id() using "iommu-map" and 
"iommu-map-mask".
+ * Convenience wrapper around of_map_id() using "iommu-map", "#iommu-cells",
+ * and "iommu-map-mask".
  *
  * 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)
 {
-       return of_map_id(np, id, "iommu-map", "iommu-map-mask", NULL, arg);
+       return of_map_id(np, id, "iommu-map", "#iommu-cells", "iommu-map-mask", 
NULL, arg);
 }
 EXPORT_SYMBOL_GPL(of_map_iommu_id);
 
@@ -2229,17 +2311,20 @@ EXPORT_SYMBOL_GPL(of_map_iommu_id);
  *     to match any. If non-NULL, only map entries targeting this node will
  *     be matched.
  * @arg: pointer to a &struct of_phandle_args for the result. On success,
- *     @arg->args[0] contains the translated ID. If a map entry was matched,
- *     @arg->np holds a reference to the target node that the caller must
- *     release with of_node_put().
+ *     @arg->args_count will be set to the number of output specifier cells
+ *     and @arg->args[0..args_count-1] will contain the translated output
+ *     specifier values. If a map entry was matched, @arg->np holds a
+ *     reference to the target node that the caller must release with
+ *     of_node_put().
  *
- * Convenience wrapper around of_map_id() using "msi-map" and "msi-map-mask".
+ * Convenience wrapper around of_map_id() using "msi-map", "#msi-cells",
+ * and "msi-map-mask".
  *
  * Return: 0 on success or a standard error code on failure.
  */
 int of_map_msi_id(const struct device_node *np, u32 id,
                  const struct device_node *filter_np, struct of_phandle_args 
*arg)
 {
-       return of_map_id(np, id, "msi-map", "msi-map-mask", filter_np, arg);
+       return of_map_id(np, id, "msi-map", "#msi-cells", "msi-map-mask", 
filter_np, arg);
 }
 EXPORT_SYMBOL_GPL(of_map_msi_id);
diff --git a/include/linux/of.h b/include/linux/of.h
index 8548cd9eb4f1..51ac8539f2c3 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -462,7 +462,8 @@ 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,
+              const char *map_name, const char *cells_name,
+              const char *map_mask_name,
               const struct device_node *filter_np, struct of_phandle_args 
*arg);
 
 int of_map_iommu_id(const struct device_node *np, u32 id,
@@ -934,7 +935,8 @@ 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,
+                            const char *map_name, const char *cells_name,
+                            const char *map_mask_name,
                             const struct device_node *filter_np,
                             struct of_phandle_args *arg)
 {

-- 
2.34.1