Re: [PATCH 0/6] of: iommu-map parsing for multi-cell IOMMU
From: Robin Murphy
Date: Mon Nov 24 2025 - 11:42:52 EST
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