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

Jonathan Cameron
2025-10-29T17:11:28Z

On Mon, 27 Oct 2025 15:25:52 +0530
"Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org> wrote:

> 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/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

I'm not keen on seeing ifdefs in a file where it isn't already local style.
This is probably better done with a second c file, appropriate header
and Kconfig / Makefile magic to control whether it is built.

> +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)
Better to have error case out of line.
if (ret != RSI_SUCCESS)
return;

__devm_auxiliary_device_create(

It's both more natural for reviewers of the code and makes it easier to stick
other things after this code later if that makes sense.

> + __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

> 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

> +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);

We have a device, so maybe flip to dev_err() or better yet

return dev_err_probe(&adev->dev, ret, "Error registering with TSM\n");

That's convenient to use in a probe() even if the deferral bits are relevant and
it prints a nice string for the 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 dev_err_probe() here as well.

> + return ret;