Re: [PATCH 0/6] of: iommu-map parsing for multi-cell IOMMU

[Robin Murphy <robin.murphy@arm.com>]

On 2025-11-21 5:54 am, Charan Teja Kalla wrote:
> 
> On 11/12/2025 8:12 PM, Charan Teja Kalla wrote:
>> Hi Robin,
>>
>> Don't want to bother you with my ideas, but I can't think of other ways
>> to handle such cases of multi-map than the below. I just tried this code on
>> Qemu on top of your patches(with some nit compilation fixes) and just checked
>> if devices are added to the iommu groups.
>>
> 
> Hello Robin,
> Not sure If this is early to ask for feedback, but waiting for your
> valuable inputs here.  Thanks in advance.

Argh, sorry, I had written a whole reply, but apparently I never hit 
send, and I've been swamped with other stuff lately. Let me see if I can 
dig that out...

Robin.

> 
>> ----------------------8888---------------------------------------------
>>
>> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
>> index a511ecf21fcd..ac005e70de7d 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"
>>   
>> @@ -41,6 +42,18 @@ static int of_iommu_xlate(struct device *dev,
>>   	return ret;
>>   }
>>   
>> +static int of_iommu_configure_cb(void *arg, u32 *id_out)
>> +{
>> +	struct of_phandle_args *iommu_spec =
>> +		(struct of_phandle_args *)((void *)id_out - offsetof(struct of_phandle_args, args));
>> +	struct device *dev = arg;
>> +	int err;
>> +
>> +	err = of_iommu_xlate(dev, iommu_spec);
>> +	of_node_put(iommu_spec->np);
>> +	return err;
>> +}
>> +
>>   static int of_iommu_configure_dev_id(struct device_node *master_np,
>>   				     struct device *dev,
>>   				     const u32 *id)
>> @@ -48,12 +61,10 @@ static int of_iommu_configure_dev_id(struct device_node *master_np,
>>   	struct of_phandle_args iommu_spec = { .args_count = 1 };
>>   	int err;
>>   
>> -	err = of_map_iommu_id(master_np, *id, &iommu_spec.np, iommu_spec.args);
>> +	err = of_map_iommu_id(master_np, *id, &iommu_spec.np, iommu_spec.args,
>> +			dev_is_platform(dev) ? true : false, dev, of_iommu_configure_cb);
>> - 	if (err)
>> - 		return err;
>> -
>> -	err = of_iommu_xlate(dev, &iommu_spec);
>> -	of_node_put(iommu_spec.np);
>>   	return err;
>>   }
>>   
>> diff --git a/drivers/of/base.c b/drivers/of/base.c
>> index a4fd4a4f720b..8abe36c17309 100644
>> --- a/drivers/of/base.c
>> +++ b/drivers/of/base.c
>> @@ -2085,16 +2085,21 @@ static bool of_check_bad_map(const __be32 *map, int len)
>>    */
>>   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 device_node **target, u32 *id_out)
>> +	      struct device_node **target, u32 *id_out, bool multi_map,
>> +	      void *arg, of_map_id_cb cb)
>>   {
>>   	u32 map_mask, masked_id;
>>   	int map_bytes, map_len, offset = 0;
>>   	bool bad_map = false;
>>   	const __be32 *map = NULL;
>> +	bool mapped_multi_id = false;
>>   
>>   	if (!np || !map_name || !cells_name || (!target && !id_out))
>>   		return -EINVAL;
>>   
>> +	if (multi_map && !cb)
>> +		return -EINVAL;
>> +
>>   	map = of_get_property(np, map_name, &map_bytes);
>>   	if (!map) {
>>   		if (target)
>> @@ -2189,16 +2194,29 @@ int of_map_id(const struct device_node *np, u32 id, const char *map_name,
>>   		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;
>> +
>> +		if (multi_map) {
>> +			if (cb(arg, id_out))
>> +				return -EINVAL;
>> +
>> +			mapped_multi_id = true;
>> +			continue;
>> +		}
>> +
>> +		goto translated;
>>   	}
>>   
>> +	if (mapped_multi_id)
>> +		return 0;
>> +
>>   	pr_info("%pOF: no %s translation for id 0x%x on %pOF\n", np, map_name,
>>   		id, target && *target ? *target : NULL);
>>   
>>   	/* Bypasses translation */
>>   	if (id_out)
>>   		*id_out = id;
>> -	return 0;
>> +translated:
>> +	return cb ? cb(arg, id_out) : 0;
>>   
>>   err_map_len:
>>   	pr_err("%pOF: Error: Bad %s length: %d\n", np, map_name, map_bytes);
>> diff --git a/include/linux/of.h b/include/linux/of.h
>> index 183be897b088..84a24c2a1041 100644
>> --- a/include/linux/of.h
>> +++ b/include/linux/of.h
>> @@ -24,6 +24,7 @@
>>   
>>   typedef u32 phandle;
>>   typedef u32 ihandle;
>> +typedef int (*of_map_id_cb)(void *arg, u32 *id_out);
>>   
>>   struct property {
>>   	char	*name;
>> @@ -458,7 +459,8 @@ 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 *cells_name, const char *map_mask_name,
>> -	      struct device_node **target, u32 *id_out);
>> +	      struct device_node **target, u32 *id_out,
>> +	      bool multi_map, void *arg, of_map_id_cb cb);
>>   
>>   phys_addr_t of_dma_get_max_cpu_address(struct device_node *np);
>>   
>> @@ -1436,17 +1438,18 @@ 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 device_node **target, u32 *id_out)
>> +				  struct device_node **target, u32 *id_out,
>> +				  bool multi_map, void *arg, of_map_id_cb cb)
>>   {
>>   	return of_map_id(np, id, "iommu-map", "#iommu-cells", "iommu-map-mask",
>> -			 target, id_out);
>> +			 target, id_out, multi_map, arg, cb);
>>   }
>>   
>>   static inline int of_map_msi_id(const struct device_node *np, u32 id,
>>   				struct device_node **target, u32 *id_out)
>>   {
>>   	return of_map_id(np, id, "msi-map", "#msi-cells", "msi-map-mask",
>> -			 target, id_out);
>> +			 target, id_out, false, NULL, NULL);
>>   }
>>   
>>   #define of_for_each_phandle(it, err, np, ln, cn, cc)			
>> -----------------------------------------------------------------------
>>
>> full patch is at: https://github.com/charan-kalla-oss/linux-next/commits/refs/for/iommu_map
>