[PATCH v2 0/2] Support remoteproc fixed device index from DT aliases

[PATCH v2 0/2] Support remoteproc fixed device index from DT aliases

[Arnaud Pouliquen]

On systems with multiple remote processors, the remoteproc device
enumeration is not stable as it depends on the probe ordering.
As a result, the /sys/class/remoteproc/remoteproc<x> entries do not
always refer to the same remote processor instance, which complicates
userspace applications.

This series:

- Introduces support for "rproc" device tree aliases to fix remoteproc device
  names and their corresponding /sys/class/remoteproc/remoteproc<x> entries.
- Updates the keystone_remoteproc driver, which also uses DT aliases, to adopt
  a common RPROC_ALIAS definition. Although it already uses the "rproc" alias
  to construct the firmware name, the change proposed in this series should be
  compatible.

Please refer to the patch commit messages for details on the implementation.

Arnaud Pouliquen (2):
  remoteproc: core: support fixed device index from DT aliases
  remoteproc: keystone: use RPROC_ALIAS definition

 drivers/remoteproc/keystone_remoteproc.c |  2 +-
 drivers/remoteproc/remoteproc_core.c     | 40 ++++++++++++++++++++++--
 include/linux/remoteproc.h               |  3 ++
 3 files changed, 42 insertions(+), 3 deletions(-)


base-commit: 63804fed149a6750ffd28610c5c1c98cce6bd377
-- 
2.43.0

[PATCH v2 1/2] remoteproc: core: support fixed device index from DT aliases

[Arnaud Pouliquen]

On systems with multiple remote processors, the remoteproc device
enumeration is not stable as it depends on the probe ordering.
As a result, the /sys/class/remoteproc/remoteproc<x> entries do not
always refer to the same remote processor instance, which complicates
userspace applications.

Inspired by the SPI implementation, this commit allows board-specific
numbering to be defined in device tree while still supporting dynamically
registered remote processors.

For instance, on STM32MP25 Soc this can be used by defining:

    aliases {
        rproc0 = &m33_rproc;
        rproc1 = &m0_rproc;
    };

When a "rproc<x>" DT alias is present, use it to assign a fixed
"/sys/class/remoteproc/remoteproc<x>" entry.
If no remoteproc alias is defined, keep the legacy index allocation.
If only some remoteproc instances have an alias, allocate dynamic
index starting after the highest alias index declared.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
---
V2:
- Introduces rproc_get_index based on Mathieu Poirier's suggestion.
  An update compared to Mathieu's version is that the call to
  ida_alloc_range is retained if an alias is found for the remote device,
  to balance with ida_free().
- Rename DT alias stem from "remoteproc" to "rproc" to be consistent with
  keytone driver.
---
 drivers/remoteproc/remoteproc_core.c | 40 ++++++++++++++++++++++++++--
 include/linux/remoteproc.h           |  3 +++
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index aada2780b343..38d6eb1c9483 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -2433,6 +2433,43 @@ static int rproc_alloc_ops(struct rproc *rproc, const struct rproc_ops *ops)
 	return 0;
 }
 
+/**
+ * rproc_get_index - assign a unique device index for a remote processor
+ * @dev: device associated with the remote processor
+ *
+ * Look for a static index coming from the "rproc" DT alias
+ * (e.g. "rproc0"). If none is found, start allocating
+ * dynamic IDs after the highest alias in use.
+ *
+ * Return: a non-negative index on success, or a negative error code on failure.
+ */
+static int rproc_get_index(struct device *dev)
+{
+	int index;
+
+	/* No DT to deal with */
+	if (!dev->of_node)
+		goto legacy;
+
+	/* See if an alias has been assigned to this remoteproc */
+	index = of_alias_get_id(dev->of_node, RPROC_ALIAS);
+	if (index >= 0)
+		return  ida_alloc_range(&rproc_dev_index, index, index,
+					GFP_KERNEL);
+	/*
+	 * No alias has been assigned to this remoteproc device. See if any
+	 * "rproc" aliases have been assigned and start allocating after
+	 * the highest one if it is the case.
+	 */
+	index = of_alias_get_highest_id(RPROC_ALIAS);
+	if (index >= 0)
+		return ida_alloc_range(&rproc_dev_index, index + 1, ~0,
+				       GFP_KERNEL);
+
+legacy:
+	return ida_alloc(&rproc_dev_index, GFP_KERNEL);
+}
+
 /**
  * rproc_alloc() - allocate a remote processor handle
  * @dev: the underlying device
@@ -2481,8 +2518,7 @@ struct rproc *rproc_alloc(struct device *dev, const char *name,
 	rproc->dev.driver_data = rproc;
 	idr_init(&rproc->notifyids);
 
-	/* Assign a unique device index and name */
-	rproc->index = ida_alloc(&rproc_dev_index, GFP_KERNEL);
+	rproc->index = rproc_get_index(dev);
 	if (rproc->index < 0) {
 		dev_err(dev, "ida_alloc failed: %d\n", rproc->index);
 		goto put_device;
diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
index b4795698d8c2..3feb2456ecc4 100644
--- a/include/linux/remoteproc.h
+++ b/include/linux/remoteproc.h
@@ -503,6 +503,9 @@ enum rproc_features {
 	RPROC_MAX_FEATURES,
 };
 
+ /* device tree remoteproc Alias stem */
+ #define RPROC_ALIAS "rproc"
+
 /**
  * struct rproc - represents a physical remote processor device
  * @node: list node of this rproc object
-- 
2.43.0

Re: [PATCH v2 1/2] remoteproc: core: support fixed device index from DT aliases

[Peng Fan]

On Wed, Jan 28, 2026 at 11:31:17AM +0100, Arnaud Pouliquen wrote:
>On systems with multiple remote processors, the remoteproc device
>enumeration is not stable as it depends on the probe ordering.
>As a result, the /sys/class/remoteproc/remoteproc<x> entries do not
>always refer to the same remote processor instance, which complicates
>userspace applications.
>
>Inspired by the SPI implementation, this commit allows board-specific
>numbering to be defined in device tree while still supporting dynamically
>registered remote processors.
>
>For instance, on STM32MP25 Soc this can be used by defining:
>
>    aliases {
>        rproc0 = &m33_rproc;
>        rproc1 = &m0_rproc;
>    };
>
>When a "rproc<x>" DT alias is present, use it to assign a fixed
>"/sys/class/remoteproc/remoteproc<x>" entry.
>If no remoteproc alias is defined, keep the legacy index allocation.
>If only some remoteproc instances have an alias, allocate dynamic
>index starting after the highest alias index declared.
>
>Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>

Tested this patch on i.MX943-EVK(patches for this platform still in my local)
with dual CM7 and one CM33S:
/sys/devices/platform/imx943-cm70/remoteproc/remoteproc1/firmware
/sys/devices/platform/imx943-cm33s/remoteproc/remoteproc0/firmware
/sys/devices/platform/imx943-cm71/remoteproc/remoteproc2/firmware

Tested-by: Peng Fan <peng.fan@nxp.com>

One nit below:

>---
>V2:
>- Introduces rproc_get_index based on Mathieu Poirier's suggestion.
>  An update compared to Mathieu's version is that the call to
>  ida_alloc_range is retained if an alias is found for the remote device,
>  to balance with ida_free().
>- Rename DT alias stem from "remoteproc" to "rproc" to be consistent with
>  keytone driver.
>---
> drivers/remoteproc/remoteproc_core.c | 40 ++++++++++++++++++++++++++--
> include/linux/remoteproc.h           |  3 +++
> 2 files changed, 41 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
>index aada2780b343..38d6eb1c9483 100644
>--- a/drivers/remoteproc/remoteproc_core.c
>+++ b/drivers/remoteproc/remoteproc_core.c
>@@ -2433,6 +2433,43 @@ static int rproc_alloc_ops(struct rproc *rproc, const struct rproc_ops *ops)
> 	return 0;
> }
> 
>+/**
>+ * rproc_get_index - assign a unique device index for a remote processor
>+ * @dev: device associated with the remote processor
>+ *
>+ * Look for a static index coming from the "rproc" DT alias
>+ * (e.g. "rproc0"). If none is found, start allocating
>+ * dynamic IDs after the highest alias in use.
>+ *
>+ * Return: a non-negative index on success, or a negative error code on failure.
>+ */
>+static int rproc_get_index(struct device *dev)
>+{
>+	int index;
>+
>+	/* No DT to deal with */
>+	if (!dev->of_node)
>+		goto legacy;
>+
>+	/* See if an alias has been assigned to this remoteproc */
>+	index = of_alias_get_id(dev->of_node, RPROC_ALIAS);
>+	if (index >= 0)
>+		return  ida_alloc_range(&rproc_dev_index, index, index,
>+					GFP_KERNEL);

Nit: "return ida_alloc_range"

Regards,
Peng

Re: [PATCH v2 1/2] remoteproc: core: support fixed device index from DT aliases

[Arnaud POULIQUEN]

Hi Peng,

On 2/4/26 01:57, Peng Fan wrote:
> On Wed, Jan 28, 2026 at 11:31:17AM +0100, Arnaud Pouliquen wrote:
>> On systems with multiple remote processors, the remoteproc device
>> enumeration is not stable as it depends on the probe ordering.
>> As a result, the /sys/class/remoteproc/remoteproc<x> entries do not
>> always refer to the same remote processor instance, which complicates
>> userspace applications.
>>
>> Inspired by the SPI implementation, this commit allows board-specific
>> numbering to be defined in device tree while still supporting dynamically
>> registered remote processors.
>>
>> For instance, on STM32MP25 Soc this can be used by defining:
>>
>>     aliases {
>>         rproc0 = &m33_rproc;
>>         rproc1 = &m0_rproc;
>>     };
>>
>> When a "rproc<x>" DT alias is present, use it to assign a fixed
>> "/sys/class/remoteproc/remoteproc<x>" entry.
>> If no remoteproc alias is defined, keep the legacy index allocation.
>> If only some remoteproc instances have an alias, allocate dynamic
>> index starting after the highest alias index declared.
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
> 
> Tested this patch on i.MX943-EVK(patches for this platform still in my local)
> with dual CM7 and one CM33S:
> /sys/devices/platform/imx943-cm70/remoteproc/remoteproc1/firmware
> /sys/devices/platform/imx943-cm33s/remoteproc/remoteproc0/firmware
> /sys/devices/platform/imx943-cm71/remoteproc/remoteproc2/firmware
> 
> Tested-by: Peng Fan <peng.fan@nxp.com>
> 
> One nit below:
> 
>> ---
>> V2:
>> - Introduces rproc_get_index based on Mathieu Poirier's suggestion.
>>   An update compared to Mathieu's version is that the call to
>>   ida_alloc_range is retained if an alias is found for the remote device,
>>   to balance with ida_free().
>> - Rename DT alias stem from "remoteproc" to "rproc" to be consistent with
>>   keytone driver.
>> ---
>> drivers/remoteproc/remoteproc_core.c | 40 ++++++++++++++++++++++++++--
>> include/linux/remoteproc.h           |  3 +++
>> 2 files changed, 41 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
>> index aada2780b343..38d6eb1c9483 100644
>> --- a/drivers/remoteproc/remoteproc_core.c
>> +++ b/drivers/remoteproc/remoteproc_core.c
>> @@ -2433,6 +2433,43 @@ static int rproc_alloc_ops(struct rproc *rproc, const struct rproc_ops *ops)
>> 	return 0;
>> }
>>
>> +/**
>> + * rproc_get_index - assign a unique device index for a remote processor
>> + * @dev: device associated with the remote processor
>> + *
>> + * Look for a static index coming from the "rproc" DT alias
>> + * (e.g. "rproc0"). If none is found, start allocating
>> + * dynamic IDs after the highest alias in use.
>> + *
>> + * Return: a non-negative index on success, or a negative error code on failure.
>> + */
>> +static int rproc_get_index(struct device *dev)
>> +{
>> +	int index;
>> +
>> +	/* No DT to deal with */
>> +	if (!dev->of_node)
>> +		goto legacy;
>> +
>> +	/* See if an alias has been assigned to this remoteproc */
>> +	index = of_alias_get_id(dev->of_node, RPROC_ALIAS);
>> +	if (index >= 0)
>> +		return  ida_alloc_range(&rproc_dev_index, index, index,
>> +					GFP_KERNEL);
> 
> Nit: "return ida_alloc_range"

Thanks for the test and the review!
I will send a V3

Arnaud

> 
> Regards,
> Peng

[PATCH v2 2/2] remoteproc: keystone: use RPROC_ALIAS definition

[Arnaud Pouliquen]

The RPROC_ALIAS definition was introduced in remoteproc.h.
Reuse it for of_alias_get_id()to to align alias handling across
the code.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
---
 drivers/remoteproc/keystone_remoteproc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/remoteproc/keystone_remoteproc.c b/drivers/remoteproc/keystone_remoteproc.c
index 4d6550b48567..cf8288d17afd 100644
--- a/drivers/remoteproc/keystone_remoteproc.c
+++ b/drivers/remoteproc/keystone_remoteproc.c
@@ -378,7 +378,7 @@ static int keystone_rproc_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
-	dsp_id = of_alias_get_id(np, "rproc");
+	dsp_id = of_alias_get_id(np, RPROC_ALIAS);
 	if (dsp_id < 0) {
 		dev_warn(dev, "device does not have an alias id\n");
 		return dsp_id;
-- 
2.43.0