firmware: smccc: Support optional Arm SMCCC SOC_ID name

Issue Number 1.6 of the Arm SMC Calling Convention introduces an optional
SOC_ID name string.  If implemented, point the 'machine' field of the SoC
Device Attributes at this string so that it will appear under
/sys/bus/soc/devices/soc0/machine.

On Arm SMC compliant SoCs, this will allow things like 'lscpu' to
eventually get a SoC provider model name from there rather than each
tool/utility needing to get a possibly inconsistent, obsolete, or incorrect
model/machine name from its own hardcoded model/machine name table.

Signed-off-by: Paul Benoit <paul@os.amperecomputing.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Mark Rutland <mark.rutland@arm.com>
Message-Id: <20250219005932.3466-1-paul@os.amperecomputing.com>
(sudeep.holla: Dropped regsize variable and used 8 instead as Mark suggested)
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

diff --git a/drivers/firmware/smccc/soc_id.c b/drivers/firmware/smccc/soc_id.c
index 1990263fbba0e026bdb25017856a72b512c52ece..c24b3fca1cfe3f41bf3ff510120e9db06059ae5a 100644 (file)
--- 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 67f6fdf2e7cd846ed599a32400e94af287509d07..eb7eab04755acb6e3c73a9509b0aab172f6509a5 100644 (file)
--- 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*/