Re: [PATCH v16 3/3] of: Respect #{iommu,msi}-cells in maps

[Neil Armstrong <neil.armstrong@xxxxxxxxxx>]

Hi,

On 6/3/26 09:13, Vijayanand Jitta wrote:
> 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  | 168 +++++++++++++++++++++++++++++++++++++++++------------
>   include/linux/of.h |   6 +-
>   2 files changed, 135 insertions(+), 39 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index d658c2620135..ac7961cbab94 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -2116,19 +2116,49 @@ 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>;
So the sm8650 PCIe controllers has:

pcie@1c08000:
                        iommu-map = <0     &apps_smmu 0x1480 0x1>,
                                    <0x100 &apps_smmu 0x1481 0x1>;

and

pcie@1c00000:

                        iommu-map = <0     &apps_smmu 0x1400 0x1>,
                                    <0x100 &apps_smmu 0x1401 0x1>;

and apps_smmu has #iommu-cells = <2>, but gets flagged at wrong:

[    7.538800] OF: /soc@0/pcie@1c08000: iommu-map has 1-cell entries targeting 
2-cell #iommu-cells, treating as 1-cell output

Returning false in of_check_bad_map() triggers:

[    7.642680] OF: /soc@0/pcie@1c08000: Unsupported iommu-map - cannot handle 
256-ID range with 2-cell output specifier

I don't understand the issue here, we use 2 cells as expected by
the iommu-cells, so why is it wrong ? can somebody explain in
comprehensive words ? I'm super confused, it worked like a charm until now.

Neil

> + */
> +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: pointer to an optional filter node, or NULL to allow bypass.
>    *    If non-NULL, the map property must exist (-ENODEV if absent). If
>    *    *filter_np is also non-NULL, only entries targeting that node match.
>    * @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
> @@ -2137,19 +2167,21 @@ 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,
>                struct device_node * const *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)
> +       if (!np || !map_name || !cells_name || !arg)
>                 return -EINVAL;
>         /* Ensure bypass/no-match success never returns a stale target node. */
>         arg->np = NULL;
>   
> -	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;
> @@ -2159,11 +2191,9 @@ 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;
> @@ -2176,39 +2206,93 @@ 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;
>   
> +		/*
> +                * Assume 1-cell output specifier if the target node lacks the
> +                * #cells property, for backward compatibility with controllers
> +                * that predate the property (e.g. arm,gic-v2m-frame).
> +                */
> +               if (bad_map || of_property_read_u32(phandle_node, cells_name, 
> &cells))
> +                       cells = 1;
> +
> +               if (cells > MAX_PHANDLE_ARGS) {
> +                       pr_err("%pOF: %s cell count %d exceeds maximum\n",
> +                              phandle_node, cells_name, cells);
> +                       of_node_put(phandle_node);
> +                       return -EINVAL;
> +               }
> +
> +               if (offset == 0 && cells == 2) {
> +                       bad_map = of_check_bad_map(map, map_len);
> +                       if (bad_map) {
> +                               pr_warn_once("%pOF: %s has 1-cell entries targeting 
> 2-cell %s, treating as 1-cell output\n",
> +                                            np, map_name, cells_name);
> +                               cells = 1;
> +                       }
> +               }
> +
> +               if (map_len - offset < 3 + cells) {
> +                       of_node_put(phandle_node);
> +                       goto err_map_len;
> +               }
> +
> +               out_base = map + offset + 2;
> +               offset += 3 + cells;
> +
> +               id_len = be32_to_cpup(map + offset - 1);
> +               id_off = masked_id - id_base;
> +               if (masked_id < id_base || id_off >= id_len) {
> +                       of_node_put(phandle_node);
> +                       continue;
> +               }
> +               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;
> +               }
> +
>                 if (filter_np && *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,
> +                       cells ? be32_to_cpup(out_base) : 0,
> +                       id_len, id,
> +                       cells ? id_off + be32_to_cpup(out_base) : id_off);
>                 return 0;
>         }
>   
> @@ -2219,6 +2303,10 @@ 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);
>   
> @@ -2228,18 +2316,21 @@ 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);
>   
> @@ -2252,17 +2343,20 @@ EXPORT_SYMBOL_GPL(of_map_iommu_id);
>    *    If non-NULL, the map property must exist (-ENODEV if absent). If
>    *    *filter_np is also non-NULL, only entries targeting that node match.
>    * @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,
>                   struct device_node * const *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 ea50b45d9ff7..374b249766a2 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -465,7 +465,8 @@ 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,
>                struct device_node * const *filter_np,
>                struct of_phandle_args *arg);
>   
> @@ -950,7 +951,8 @@ 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,
>                              struct device_node * const *filter_np,
>                              struct of_phandle_args *arg)
>   {