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

[Charan Teja Kalla <charan.kalla@oss.qualcomm.com>]

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.

> ----------------------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