feat(allwinner): add SMCCC SOCID support

The Allwinner SID device holds a 16-bit SoC identifier, which we already
use in our code.

Export this number through the generic SMCCC SOCID interface, to allow
an architectural identification of an Allwinner SoC. This enables access
to this information from non-secure world, simplifies generic drivers
(ACPI comes to mind), and gives easy and precise access to the SoC ID
from userland in OSes like Linux.

Change-Id: I91753046b2ae5408ca7bc0b864fcd97d24c8267c
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

plat/allwinner/common/include/sunxi_def.h

@@ -20,4 +20,7 @@
 #define SUNXI_SOC_H616			0x1823
 #define SUNXI_SOC_R329			0x1851
 
+#define JEDEC_ALLWINNER_BKID		9U
+#define JEDEC_ALLWINNER_MFID		0x9eU
+
 #endif /* SUNXI_DEF_H */

plat/allwinner/common/sunxi_common.c

@@ -8,7 +8,9 @@
 
 #include <common/debug.h>
 #include <lib/mmio.h>
+#include <lib/smccc.h>
 #include <lib/xlat_tables/xlat_tables_v2.h>
+#include <services/arm_arch_svc.h>
 
 #include <sunxi_def.h>
 #include <sunxi_mmap.h>
@@ -157,3 +159,29 @@ int sunxi_init_platform_r_twi(uint16_t socid, bool use_rsb)
 
 	return 0;
 }
+
+int32_t plat_is_smccc_feature_available(u_register_t fid)
+{
+	switch (fid) {
+	case SMCCC_ARCH_SOC_ID:
+		return SMC_ARCH_CALL_SUCCESS;
+	default:
+		return SMC_ARCH_CALL_NOT_SUPPORTED;
+	}
+}
+
+int32_t plat_get_soc_version(void)
+{
+	int32_t ret;
+
+	ret = SOC_ID_SET_JEP_106(JEDEC_ALLWINNER_BKID, JEDEC_ALLWINNER_MFID);
+
+	return ret | (sunxi_read_soc_id() & SOC_ID_IMPL_DEF_MASK);
+}
+
+int32_t plat_get_soc_revision(void)
+{
+	uint32_t reg = mmio_read_32(SRAM_VER_REG);
+
+	return reg & GENMASK_32(7, 0);
+}