[PATCH v2 02/12] firmware: smccc: coco: Manage arm-smccc platform device and CCA auxiliary drivers

Aneesh Kumar K.V (Arm)
2025-10-27T09:51:27Z

Make the SMCCC driver responsible for registering the arm-smccc platform
device and after confirming the relevant SMCCC function IDs, create
the arm_cca_guest auxiliary device.

Also update the arm-cca-guest driver to use the auxiliary device
interface instead of the platform device (arm-cca-dev). The removal of
the platform device registration will follow in a subsequent patch,
allowing this change to be applied without immediately breaking existing
userspace dependencies [1].

[1] https://lore.kernel.org/all/4a7d84b2-2ec4-4773-a2d5-7b63d5c683cf@arm.com
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
arch/arm64/include/asm/rsi.h | 2 +-
arch/arm64/kernel/rsi.c | 2 +-
drivers/firmware/smccc/Kconfig | 1 +
drivers/firmware/smccc/smccc.c | 37 ++++++++++++
drivers/virt/coco/arm-cca-guest/Kconfig | 1 +
drivers/virt/coco/arm-cca-guest/Makefile | 2 +
.../{arm-cca-guest.c => arm-cca.c} | 57 +++++++++----------
7 files changed, 71 insertions(+), 31 deletions(-)
rename drivers/virt/coco/arm-cca-guest/{arm-cca-guest.c => arm-cca.c} (85%)

diff --git a/arch/arm64/include/asm/rsi.h b/arch/arm64/include/asm/rsi.h
index 88b50d660e85..2d2d363aaaee 100644
--- a/arch/arm64/include/asm/rsi.h
+++ b/arch/arm64/include/asm/rsi.h
@@ -10,7 +10,7 @@
#include <linux/jump_label.h>
#include <asm/rsi_cmds.h>

-#define RSI_PDEV_NAME "arm-cca-dev"
+#define RSI_DEV_NAME "arm-rsi-dev"

DECLARE_STATIC_KEY_FALSE(rsi_present);

diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
index c64a06f58c0b..5d711942e543 100644
--- a/arch/arm64/kernel/rsi.c
+++ b/arch/arm64/kernel/rsi.c
@@ -160,7 +160,7 @@ void __init arm64_rsi_init(void)
}

static struct platform_device rsi_dev = {
- .name = RSI_PDEV_NAME,
+ .name = "arm-cca-dev",
.id = PLATFORM_DEVID_NONE
};

diff --git a/drivers/firmware/smccc/Kconfig b/drivers/firmware/smccc/Kconfig
index 15e7466179a6..2b6984757241 100644
--- a/drivers/firmware/smccc/Kconfig
+++ b/drivers/firmware/smccc/Kconfig
@@ -8,6 +8,7 @@ config HAVE_ARM_SMCCC
config HAVE_ARM_SMCCC_DISCOVERY
bool
depends on ARM_PSCI_FW
+ select AUXILIARY_BUS
default y
help
SMCCC v1.0 lacked discoverability and hence PSCI v1.0 was updated
diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c
index bdee057db2fd..3dbf0d067cc5 100644
--- a/drivers/firmware/smccc/smccc.c
+++ b/drivers/firmware/smccc/smccc.c
@@ -10,7 +10,12 @@
#include <linux/arm-smccc.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
+#include <linux/auxiliary_bus.h>
+
#include <asm/archrandom.h>
+#ifdef CONFIG_ARM64
+#include <asm/rsi_cmds.h>
+#endif

static u32 smccc_version = ARM_SMCCC_VERSION_1_0;
static enum arm_smccc_conduit smccc_conduit = SMCCC_CONDUIT_NONE;
@@ -81,10 +86,42 @@ bool arm_smccc_hypervisor_has_uuid(const uuid_t *hyp_uuid)
}
EXPORT_SYMBOL_GPL(arm_smccc_hypervisor_has_uuid);

+#ifdef CONFIG_ARM64
+static void __init register_rsi_device(struct platform_device *pdev)
+{
+ unsigned long ver_lower, ver_higher;
+ unsigned long ret = rsi_request_version(RSI_ABI_VERSION,
+ &ver_lower,
+ &ver_higher);
+
+ if (ret == RSI_SUCCESS)
+ __devm_auxiliary_device_create(&pdev->dev,
+ "arm_cca_guest", RSI_DEV_NAME, NULL, 0);
+
+}
+#else
+static void __init register_rsi_device(struct platform_device *pdev)
+{
+
+}
+#endif
+
static int __init smccc_devices_init(void)
{
struct platform_device *pdev;

+ pdev = platform_device_register_simple("arm-smccc",
+ PLATFORM_DEVID_NONE, NULL, 0);
+ if (IS_ERR(pdev)) {
+ pr_err("arm-smccc: could not register device: %ld\n", PTR_ERR(pdev));
+ } else {
+ /*
+ * Register the RMI and RSI devices only when firmware exposes
+ * the required SMCCC function IDs at a supported revision.
+ */
+ register_rsi_device(pdev);
+ }
+
if (smccc_trng_available) {
pdev = platform_device_register_simple("smccc_trng", -1,
NULL, 0);
diff --git a/drivers/virt/coco/arm-cca-guest/Kconfig b/drivers/virt/coco/arm-cca-guest/Kconfig
index 3f0f013f03f1..a42359a90558 100644
--- a/drivers/virt/coco/arm-cca-guest/Kconfig
+++ b/drivers/virt/coco/arm-cca-guest/Kconfig
@@ -2,6 +2,7 @@ config ARM_CCA_GUEST
tristate "Arm CCA Guest driver"
depends on ARM64
select TSM_REPORTS
+ select AUXILIARY_BUS
help
The driver provides userspace interface to request and
attestation report from the Realm Management Monitor(RMM).
diff --git a/drivers/virt/coco/arm-cca-guest/Makefile b/drivers/virt/coco/arm-cca-guest/Makefile
index 69eeba08e98a..75a120e24fda 100644
--- a/drivers/virt/coco/arm-cca-guest/Makefile
+++ b/drivers/virt/coco/arm-cca-guest/Makefile
@@ -1,2 +1,4 @@
# SPDX-License-Identifier: GPL-2.0-only
obj-$(CONFIG_ARM_CCA_GUEST) += arm-cca-guest.o
+
+arm-cca-guest-y += arm-cca.o
diff --git a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c b/drivers/virt/coco/arm-cca-guest/arm-cca.c
similarity index 85%
rename from drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
rename to drivers/virt/coco/arm-cca-guest/arm-cca.c
index 0c9ea24a200c..dc96171791db 100644
--- a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
+++ b/drivers/virt/coco/arm-cca-guest/arm-cca.c
@@ -3,6 +3,7 @@
* Copyright (C) 2023 ARM Ltd.
*/

+#include <linux/auxiliary_bus.h>
#include <linux/arm-smccc.h>
#include <linux/cc_platform.h>
#include <linux/kernel.h>
@@ -181,52 +182,50 @@ static int arm_cca_report_new(struct tsm_report *report, void *data)
return ret;
}

-static const struct tsm_report_ops arm_cca_tsm_ops = {
+static const struct tsm_report_ops arm_cca_tsm_report_ops = {
.name = KBUILD_MODNAME,
.report_new = arm_cca_report_new,
};

-/**
- * arm_cca_guest_init - Register with the Trusted Security Module (TSM)
- * interface.
- *
- * Return:
- * * %0 - Registered successfully with the TSM interface.
- * * %-ENODEV - The execution context is not an Arm Realm.
- * * %-EBUSY - Already registered.
- */
-static int __init arm_cca_guest_init(void)
+static void unregister_cca_tsm_report(void *data)
+{
+ tsm_report_unregister(&arm_cca_tsm_report_ops);
+}
+
+static int cca_devsec_tsm_probe(struct auxiliary_device *adev,
+ const struct auxiliary_device_id *id)
{
int ret;

if (!is_realm_world())
return -ENODEV;

- ret = tsm_report_register(&arm_cca_tsm_ops, NULL);
- if (ret < 0)
+ ret = tsm_report_register(&arm_cca_tsm_report_ops, NULL);
+ if (ret < 0) {
pr_err("Error %d registering with TSM\n", ret);
+ return ret;
+ }

- return ret;
-}
-module_init(arm_cca_guest_init);
+ ret = devm_add_action_or_reset(&adev->dev, unregister_cca_tsm_report, NULL);
+ if (ret < 0) {
+ pr_err("Error %d registering devm action\n", ret);
+ return ret;
+ }

-/**
- * arm_cca_guest_exit - unregister with the Trusted Security Module (TSM)
- * interface.
- */
-static void __exit arm_cca_guest_exit(void)
-{
- tsm_report_unregister(&arm_cca_tsm_ops);
+ return 0;
}
-module_exit(arm_cca_guest_exit);

-/* modalias, so userspace can autoload this module when RSI is available */
-static const struct platform_device_id arm_cca_match[] __maybe_unused = {
- { RSI_PDEV_NAME, 0},
- { }
+static const struct auxiliary_device_id cca_devsec_tsm_id_table[] = {
+ { .name = KBUILD_MODNAME "." RSI_DEV_NAME },
+ {}
};
+MODULE_DEVICE_TABLE(auxiliary, cca_devsec_tsm_id_table);

-MODULE_DEVICE_TABLE(platform, arm_cca_match);
+static struct auxiliary_driver cca_devsec_tsm_driver = {
+ .probe = cca_devsec_tsm_probe,
+ .id_table = cca_devsec_tsm_id_table,
+};
+module_auxiliary_driver(cca_devsec_tsm_driver);
MODULE_AUTHOR("Sami Mujawar <sami.mujawar@arm.com>");
MODULE_DESCRIPTION("Arm CCA Guest TSM Driver");
MODULE_LICENSE("GPL");
--
2.43.0