From d8263a131bb05398faa72ac32be54a03e48fa197 Mon Sep 17 00:00:00 2001 From: "Aneesh Kumar K.V (Arm)" Date: Wed, 23 Sep 2026 19:33:59 +0530 Subject: [PATCH] firmware: hwrng: arm_smccc_trng: Register as an SMCCC device The SMCCC TRNG interface is a firmware-provided SMCCC service rather than a standalone platform device. Now that the SMCCC core has an SMCCC bus, create an arm-smccc-trng device for the discovered TRNG service and convert the hwrng driver to an SMCCC driver. The SMCCC id table preserves module autoloading for systems where the TRNG driver is built as a module. The sysfs device path changes from the old smccc_trng platform-device path to an arm-smccc device path. No known userspace dependency on the old path was found; a Debian Code Search lookup for the existing platform-device name/path did not find any users. Reviewed-by: Catalin Marinas Reviewed-by: Jonathan Cameron Reviewed-by: Jason Gunthorpe Reviewed-by: Sudeep Holla Tested-by: Andre Przywara Cc: Russell King Cc: Will Deacon Cc: Mark Rutland Cc: Olivia Mackall Cc: Herbert Xu Cc: Lorenzo Pieralisi Signed-off-by: Aneesh Kumar K.V (Arm) Signed-off-by: Catalin Marinas --- arch/arm/include/asm/archrandom.h | 2 +- arch/arm64/include/asm/archrandom.h | 2 +- drivers/char/hw_random/arm_smccc_trng.c | 32 ++++++++----- drivers/firmware/smccc/smccc.c | 60 +++++++++++++++++++++---- 4 files changed, 75 insertions(+), 21 deletions(-) diff --git a/arch/arm/include/asm/archrandom.h b/arch/arm/include/asm/archrandom.h index cc4714eb1a75..ee39a03ddf8a 100644 --- a/arch/arm/include/asm/archrandom.h +++ b/arch/arm/include/asm/archrandom.h @@ -2,7 +2,7 @@ #ifndef _ASM_ARCHRANDOM_H #define _ASM_ARCHRANDOM_H -static inline bool __init smccc_probe_trng(void) +static inline bool smccc_probe_trng(void) { return false; } diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h index 8babfbe31f95..7605dd81bd1e 100644 --- a/arch/arm64/include/asm/archrandom.h +++ b/arch/arm64/include/asm/archrandom.h @@ -12,7 +12,7 @@ extern bool smccc_trng_available; -static inline bool __init smccc_probe_trng(void) +static inline bool smccc_probe_trng(void) { struct arm_smccc_res res; diff --git a/drivers/char/hw_random/arm_smccc_trng.c b/drivers/char/hw_random/arm_smccc_trng.c index dcb8e7f37f25..01c1a30cbab8 100644 --- a/drivers/char/hw_random/arm_smccc_trng.c +++ b/drivers/char/hw_random/arm_smccc_trng.c @@ -16,8 +16,10 @@ #include #include #include -#include #include +#include + +#include #ifdef CONFIG_ARM64 #define ARM_SMCCC_TRNG_RND ARM_SMCCC_TRNG_RND64 @@ -94,29 +96,37 @@ static int smccc_trng_read(struct hwrng *rng, void *data, size_t max, bool wait) return copied; } -static int smccc_trng_probe(struct platform_device *pdev) +static int smccc_trng_probe(struct arm_smccc_device *sdev) { struct hwrng *trng; - trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL); + /* validate the minimum version requirement */ + if (!smccc_probe_trng()) + return -ENODEV; + + trng = devm_kzalloc(&sdev->dev, sizeof(*trng), GFP_KERNEL); if (!trng) return -ENOMEM; trng->name = "smccc_trng"; trng->read = smccc_trng_read; - return devm_hwrng_register(&pdev->dev, trng); + return devm_hwrng_register(&sdev->dev, trng); } -static struct platform_driver smccc_trng_driver = { - .driver = { - .name = "smccc_trng", - }, - .probe = smccc_trng_probe, +static const struct arm_smccc_device_id smccc_trng_id_table[] = { + { .func_id = ARM_SMCCC_TRNG_VERSION }, + {} }; -module_platform_driver(smccc_trng_driver); +MODULE_DEVICE_TABLE(arm_smccc, smccc_trng_id_table); + +static struct arm_smccc_driver smccc_trng_driver = { + .name = KBUILD_MODNAME, + .probe = smccc_trng_probe, + .id_table = smccc_trng_id_table, +}; +module_arm_smccc_driver(smccc_trng_driver); -MODULE_ALIAS("platform:smccc_trng"); MODULE_AUTHOR("Andre Przywara"); MODULE_DESCRIPTION("Arm SMCCC TRNG firmware interface support"); MODULE_LICENSE("GPL"); diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c index bdee057db2fd..67e503dac409 100644 --- a/drivers/firmware/smccc/smccc.c +++ b/drivers/firmware/smccc/smccc.c @@ -9,7 +9,8 @@ #include #include #include -#include +#include + #include static u32 smccc_version = ARM_SMCCC_VERSION_1_0; @@ -81,16 +82,59 @@ bool arm_smccc_hypervisor_has_uuid(const uuid_t *hyp_uuid) } EXPORT_SYMBOL_GPL(arm_smccc_hypervisor_has_uuid); +struct smccc_device_info { + u32 func_id; + bool requires_smc; + const char *device_name; +}; + +static const struct smccc_device_info smccc_devices[] __initconst = { + { + .func_id = ARM_SMCCC_TRNG_VERSION, + .requires_smc = false, + .device_name = "arm-smccc-trng", + }, +}; + +static bool __init smccc_probe_smccc_device(const struct smccc_device_info *smccc_dev) +{ + int ret; + struct arm_smccc_res res = {}; + + if (smccc_conduit == SMCCC_CONDUIT_NONE) + return false; + + if (smccc_dev->requires_smc && smccc_conduit != SMCCC_CONDUIT_SMC) + return false; + + if (IS_ENABLED(CONFIG_ARM) && ARM_SMCCC_IS_64(smccc_dev->func_id)) + return false; + + arm_smccc_1_1_invoke(smccc_dev->func_id, + 0, 0, 0, 0, 0, 0, 0, &res); + ret = res.a0; + + if (ret == SMCCC_RET_NOT_SUPPORTED) + return false; + + return true; +} + static int __init smccc_devices_init(void) { - struct platform_device *pdev; + struct arm_smccc_device *sdev; + const struct smccc_device_info *smccc_dev; - if (smccc_trng_available) { - pdev = platform_device_register_simple("smccc_trng", -1, - NULL, 0); - if (IS_ERR(pdev)) - pr_err("smccc_trng: could not register device: %ld\n", - PTR_ERR(pdev)); + for (int i = 0; i < ARRAY_SIZE(smccc_devices); i++) { + smccc_dev = &smccc_devices[i]; + + if (!smccc_probe_smccc_device(smccc_dev)) + continue; + + sdev = arm_smccc_device_register(smccc_dev->device_name, smccc_dev->func_id); + if (IS_ERR(sdev)) + pr_err("%s: could not register device: %pe\n", + smccc_dev->device_name, sdev); } return 0;