fix(psci): per-plat smccc version support

[DavidMCerdeira]

With S32G3 platform we misinterpreted the VENDOR_START PSCI_FEATURES
argument. The correct flag is SMCC_VERSION. This flag seems to be needed
for vendor specific calls that depend on a high-enough smccc version.
Addtionally, we make this flag per-platform, since currently supported
platforms except for S32G3 don't need this feature.

[josecm]

Shouldn't this be part of PSCI-specific code?

Also, can't we probe for the support for if the service is implemented or not and act accordingly?

[joaopeixoto13]

Since PSCI_1_1_RESET_TYPE_VENDOR_START is only needed for the S32G3 to issue vendor-specific SMCs, would it make sense to introduce a dedicated platform define, such as PLAT_PSCI_SUPPORT_RESET_TYPE_VENDOR_START?

Each platform could explicitly define this macro if it requires support for PSCI_1_1_RESET_TYPE_VENDOR_START. At the moment, this would apply only to S32G3, but it keeps the design extensible in case other platforms need the same support in the future.

Then, in psci_features_handler(), we could conditionally advertise support for PSCI_1_1_RESET_TYPE_VENDOR_START only when PLAT_PSCI_SUPPORT_RESET_TYPE_VENDOR_START is defined, for example:

src/platform/s32g3/inc/plat/psci.h

#define PLAT_PSCI_SUPPORT_RESET_TYPE_VENDOR_START 1

src/arch/armv8/psci.c

static int32_t psci_features_handler(uint32_t feature_id)
{
    int32_t ret = PSCI_E_NOT_SUPPORTED;

    switch (feature_id) {
    case PSCI_VERSION:
    case PSCI_CPU_OFF:
    case PSCI_CPU_SUSPEND_SMC32:
    case PSCI_CPU_SUSPEND_SMC64:
    case PSCI_CPU_ON_SMC32:
    case PSCI_CPU_ON_SMC64:
    case PSCI_AFFINITY_INFO_SMC32:
    case PSCI_AFFINITY_INFO_SMC64:
    case PSCI_FEATURES:
#ifdef PLAT_PSCI_SUPPORT_RESET_TYPE_VENDOR_START
    case PSCI_1_1_RESET_TYPE_VENDOR_START:
#endif
        ret = PSCI_E_SUCCESS;
        break;

    default:
        ret = PSCI_E_NOT_SUPPORTED;
        break;
    }

    return ret;
}

[joaopeixoto13]

Everything works on qemu-aarch64-virt and on s32g3

[DavidMCerdeira]

Working on RPi4