Merge tag 'smccc-update-6.15' of https://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into soc/drivers

Arm SMCCC update for v6.15

Just a single update introducing the support for the optional SOC_ID
name string from the Arm SMCCC v1.6 specification.

If the SOC_ID name string is implemented, the machine field of the SoC
Device Attributes will reflect it.

The original intent of SOC_ID was to provide a JEP-106 code for the SiP
and the SoC revision to uniquely identify the SoC. However, there has
been a request to add this optional name so that SoC firmware can
directly provide the SoC name to the OS.

This change avoids the need for frequent updates to various tools that
would otherwise require maintaining hardcoded model/machine name tables
for new SoCs.

* tag 'smccc-update-6.15' of https://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
  firmware: smccc: Support optional Arm SMCCC SOC_ID name

Link: https://lore.kernel.org/r/20250304105845.432813-1-sudeep.holla@arm.com
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

2 files changed, 120 insertions, 0 deletions

diff --git a/drivers/firmware/smccc/soc_id.c b/drivers/firmware/smccc/soc_id.c
index 1990263fbba0..c24b3fca1cfe 100644
--- a/drivers/firmware/smccc/soc_id.c
+++ b/drivers/firmware/smccc/soc_id.c
@@ -32,6 +32,85 @@
 static struct soc_device *soc_dev;
 static struct soc_device_attribute *soc_dev_attr;
 
+#ifdef CONFIG_ARM64
+
+static char __ro_after_init smccc_soc_id_name[136] = "";
+
+static inline void str_fragment_from_reg(char *dst, unsigned long reg)
+{
+	dst[0] = (reg >> 0)  & 0xff;
+	dst[1] = (reg >> 8)  & 0xff;
+	dst[2] = (reg >> 16) & 0xff;
+	dst[3] = (reg >> 24) & 0xff;
+	dst[4] = (reg >> 32) & 0xff;
+	dst[5] = (reg >> 40) & 0xff;
+	dst[6] = (reg >> 48) & 0xff;
+	dst[7] = (reg >> 56) & 0xff;
+}
+
+static char __init *smccc_soc_name_init(void)
+{
+	struct arm_smccc_1_2_regs args;
+	struct arm_smccc_1_2_regs res;
+	size_t len;
+
+	/*
+	 * Issue Number 1.6 of the Arm SMC Calling Convention
+	 * specification introduces an optional "name" string
+	 * to the ARM_SMCCC_ARCH_SOC_ID function.  Fetch it if
+	 * available.
+	 */
+	args.a0 = ARM_SMCCC_ARCH_SOC_ID;
+	args.a1 = 2;    /* SOC_ID name */
+	arm_smccc_1_2_invoke(&args, &res);
+
+	if ((u32)res.a0 == 0) {
+		/*
+		 * Copy res.a1..res.a17 to the smccc_soc_id_name string
+		 * 8 bytes at a time.  As per Issue 1.6 of the Arm SMC
+		 * Calling Convention, the string will be NUL terminated
+		 * and padded, from the end of the string to the end of the
+		 * 136 byte buffer, with NULs.
+		 */
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 0, res.a1);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 1, res.a2);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 2, res.a3);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 3, res.a4);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 4, res.a5);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 5, res.a6);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 6, res.a7);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 7, res.a8);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 8, res.a9);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 9, res.a10);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 10, res.a11);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 11, res.a12);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 12, res.a13);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 13, res.a14);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 14, res.a15);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 15, res.a16);
+		str_fragment_from_reg(smccc_soc_id_name + 8 * 16, res.a17);
+
+		len = strnlen(smccc_soc_id_name, sizeof(smccc_soc_id_name));
+		if (len) {
+			if (len == sizeof(smccc_soc_id_name))
+				pr_warn(FW_BUG "Ignoring improperly formatted name\n");
+			else
+				return smccc_soc_id_name;
+		}
+	}
+
+	return NULL;
+}
+
+#else
+
+static char __init *smccc_soc_name_init(void)
+{
+	return NULL;
+}
+
+#endif
+
 static int __init smccc_soc_init(void)
 {
 	int soc_id_rev, soc_id_version;
@@ -72,6 +151,7 @@ static int __init smccc_soc_init(void)
 	soc_dev_attr->soc_id = soc_id_str;
 	soc_dev_attr->revision = soc_id_rev_str;
 	soc_dev_attr->family = soc_id_jep106_id_str;
+	soc_dev_attr->machine = smccc_soc_name_init();
 
 	soc_dev = soc_device_register(soc_dev_attr);
 	if (IS_ERR(soc_dev)) {
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index 67f6fdf2e7cd..eb7eab04755a 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -639,5 +639,45 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
 		method;							\
 	})
 
+#ifdef CONFIG_ARM64
+
+#define __fail_smccc_1_2(___res)					\
+	do {								\
+		if (___res)						\
+			___res->a0 = SMCCC_RET_NOT_SUPPORTED;		\
+	} while (0)
+
+/*
+ * arm_smccc_1_2_invoke() - make an SMCCC v1.2 compliant call
+ *
+ * @args: SMC args are in the a0..a17 fields of the arm_smcc_1_2_regs structure
+ * @res: result values from registers 0 to 17
+ *
+ * This macro will make either an HVC call or an SMC call depending on the
+ * current SMCCC conduit. If no valid conduit is available then -1
+ * (SMCCC_RET_NOT_SUPPORTED) is returned in @res.a0 (if supplied).
+ *
+ * The return value also provides the conduit that was used.
+ */
+#define arm_smccc_1_2_invoke(args, res) ({				\
+		struct arm_smccc_1_2_regs *__args = args;		\
+		struct arm_smccc_1_2_regs *__res = res;			\
+		int method = arm_smccc_1_1_get_conduit();		\
+		switch (method) {					\
+		case SMCCC_CONDUIT_HVC:					\
+			arm_smccc_1_2_hvc(__args, __res);		\
+			break;						\
+		case SMCCC_CONDUIT_SMC:					\
+			arm_smccc_1_2_smc(__args, __res);		\
+			break;						\
+		default:						\
+			__fail_smccc_1_2(__res);			\
+			method = SMCCC_CONDUIT_NONE;			\
+			break;						\
+		}							\
+		method;							\
+	})
+#endif /*CONFIG_ARM64*/
+
 #endif /*__ASSEMBLY__*/
 #endif /*__LINUX_ARM_SMCCC_H*/