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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v16 3/3] of: Respect #{iommu,msi}-cells in maps
On 7/23/2026 6:47 PM, Neil Armstrong wrote:
> 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
>
Hi Neil,
iommu-map = <0 &apps_smmu 0x1480 0x1>,
<0x100 &apps_smmu 0x1481 0x1>;
Entries here are not 2-cell format, Even though apps_smmu declares #iommu-cells
= <2>,
this DT only supplies one output cell (0x1480/0x1481) — the trailing 0x1 is the
length field,
not a second output cell. (<id-base phandle out-base length>)
The new code detects exactly this pattern (same target phandle across all
entries, length always 1)
and falls back to treating the map as 1-cell output for backward compatibility
— hence the pr_warn_once.
It's harmless and expected, your RIDs still resolve to the correct SIDs (0 →
0x1480, 0x100 → 0x1481).
The second message is a different case and shouldn't be coming from this same
map — once the 1-cell
fallback triggers on the first entry, it applies to the whole map, so you
shouldn't hit both warnings
together on the same node. That error only fires for a genuine 2-cell output
specifier combined with
an id_len > 1, e.g.:
iommu-map = <0x0 &apps_smmu 0x1480 0x1 0x100>;
(<id-base, phandle, out0, out1, length=256>) — which isn't supported, since
there's no way to
linearly scale a multi-cell output specifier across a range of IDs.
Are you seeing that second error on the same pcie node, or a different one?
If it's the same node, can you share the exact iommu-map entry that triggers it?
Thanks,
Vijay
>> + */
>> +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)
>> {
>>
>
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