[PATCH v2 5/5] arm/arm64: smccc: Add ARCH_SOC_ID support

[Sudeep Holla <sudeep.holla@arm.com>]

SMCCC v1.2 adds a new optional function SMCCC_ARCH_SOC_ID to obtain a
SiP defined SoC identification value. Add support for the same.

Also using the SoC bus infrastructure, let us expose the platform
specific SoC atrributes under sysfs. We also provide custom sysfs for
the vendor ID as JEP-106 bank and identification code.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
 drivers/firmware/psci/Kconfig  |   9 ++
 drivers/firmware/psci/Makefile |   1 +
 drivers/firmware/psci/soc_id.c | 165 +++++++++++++++++++++++++++++++++
 include/linux/arm-smccc.h      |   5 +
 4 files changed, 180 insertions(+)
 create mode 100644 drivers/firmware/psci/soc_id.c

diff --git a/drivers/firmware/psci/Kconfig b/drivers/firmware/psci/Kconfig
index 97944168b5e6..831399338289 100644
--- a/drivers/firmware/psci/Kconfig
+++ b/drivers/firmware/psci/Kconfig
@@ -12,3 +12,12 @@ config ARM_PSCI_CHECKER
 	  The torture tests may interfere with the PSCI checker by turning CPUs
 	  on and off through hotplug, so for now torture tests and PSCI checker
 	  are mutually exclusive.
+
+config ARM_SMCCC_SOC_ID
+	bool "SoC bus device for the ARM SMCCC SOC_ID"
+	depends on ARM_PSCI_FW
+	default y if ARM_PSCI_FW
+	select SOC_BUS
+	help
+	  Include support for the SoC bus on the ARM SMCCC firmware based
+	  platforms providing some sysfs information about the SoC variant.
diff --git a/drivers/firmware/psci/Makefile b/drivers/firmware/psci/Makefile
index 1956b882470f..55596698d1ad 100644
--- a/drivers/firmware/psci/Makefile
+++ b/drivers/firmware/psci/Makefile
@@ -2,3 +2,4 @@
 #
 obj-$(CONFIG_ARM_PSCI_FW)	+= psci.o
 obj-$(CONFIG_ARM_PSCI_CHECKER)	+= psci_checker.o
+obj-$(CONFIG_ARM_SMCCC_SOC_ID)	+= soc_id.o
diff --git a/drivers/firmware/psci/soc_id.c b/drivers/firmware/psci/soc_id.c
new file mode 100644
index 000000000000..b45f2d78e12e
--- /dev/null
+++ b/drivers/firmware/psci/soc_id.c
@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2020 Arm Limited
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/bitfield.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/sys_soc.h>
+
+#define SMCCC_SOC_ID_JEP106_BANK_IDX_MASK	GENMASK(30, 24)
+/*
+ * As per the spec bits[23:16] are JEP-106 identification code with parity bit
+ * for the SiP. We can drop the parity bit.
+ */
+#define SMCCC_SOC_ID_JEP106_ID_CODE_MASK	GENMASK(22, 16)
+#define SMCCC_SOC_ID_IMP_DEF_SOC_ID_MASK	GENMASK(15, 0)
+
+/* The bank index is equal to the for continuation code bank number - 1 */
+#define JEP106_BANK_CONT_CODE(x)	\
+	(u8)(FIELD_GET(SMCCC_SOC_ID_JEP106_BANK_IDX_MASK, (x)) + 1)
+#define JEP106_ID_CODE(x)	\
+	(u8)(FIELD_GET(SMCCC_SOC_ID_JEP106_ID_CODE_MASK, (x)))
+#define IMP_DEF_SOC_ID(x)	\
+	(u16)(FIELD_GET(SMCCC_SOC_ID_IMP_DEF_SOC_ID_MASK, (x)))
+
+static int soc_id_version;
+static struct soc_device *soc_dev;
+static struct soc_device_attribute *soc_dev_attr;
+
+static int smccc_map_error_codes(unsigned long a0)
+{
+	if (a0 >= SMCCC_RET_SUCCESS)
+		return 0;
+	else if (a0 == SMCCC_RET_INVALID_PARAMETER)
+		return -EINVAL;
+	else if (a0 == SMCCC_RET_NOT_SUPPORTED)
+		return -EOPNOTSUPP;
+	return -EINVAL;
+}
+
+static int smccc_soc_id_support_check(void)
+{
+	struct arm_smccc_res res;
+
+	if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE) {
+		pr_err("%s: invalid SMCCC conduit\n", __func__);
+		return -EOPNOTSUPP;
+	}
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+			     ARM_SMCCC_ARCH_SOC_ID, &res);
+
+	return smccc_map_error_codes(res.a0);
+}
+
+static ssize_t
+jep106_cont_bank_code_show(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	return sprintf(buf, "%02x\n", JEP106_BANK_CONT_CODE(soc_id_version));
+}
+
+static DEVICE_ATTR_RO(jep106_cont_bank_code);
+
+static ssize_t
+jep106_identification_code_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%02x\n", JEP106_ID_CODE(soc_id_version));
+}
+
+static DEVICE_ATTR_RO(jep106_identification_code);
+
+static struct attribute *jep106_id_attrs[] = {
+	&dev_attr_jep106_cont_bank_code.attr,
+	&dev_attr_jep106_identification_code.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(jep106_id);
+
+static int __init smccc_soc_init(void)
+{
+	struct device *dev;
+	int ret, soc_id_rev;
+	struct arm_smccc_res res;
+	static char soc_id_str[8], soc_id_rev_str[12];
+
+	if (arm_smccc_get_version() < ARM_SMCCC_VERSION_1_2)
+		return 0;
+
+	ret = smccc_soc_id_support_check();
+	if (ret) {
+		pr_info("SMCCC SOC_ID not implemented, skipping ....\n");
+		return 0;
+	}
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_SOC_ID, 0, &res);
+
+	ret = smccc_map_error_codes(res.a0);
+	if (ret) {
+		pr_info("SMCCC SOC_ID: failed to version, Err = %d\n", ret);
+		return ret;
+	}
+
+	soc_id_version = res.a0;
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_SOC_ID, 1, &res);
+
+	ret = smccc_map_error_codes(res.a0);
+	if (ret) {
+		pr_info("SMCCC SOC_ID: failed to revision, Err = %d\n", ret);
+		return ret;
+	}
+
+	soc_id_rev = res.a0;
+
+	soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL);
+	if (!soc_dev_attr)
+		return -ENOMEM;
+
+	sprintf(soc_id_str, "0x%04x", IMP_DEF_SOC_ID(soc_id_version));
+	sprintf(soc_id_rev_str, "0x%08x", soc_id_rev);
+
+	soc_dev_attr->soc_id = soc_id_str;
+	soc_dev_attr->revision = soc_id_rev_str;
+
+	soc_dev = soc_device_register(soc_dev_attr);
+	if (IS_ERR(soc_dev)) {
+		ret = PTR_ERR(soc_dev);
+		goto free_soc;
+	}
+
+	dev = soc_device_to_device(soc_dev);
+
+	ret = devm_device_add_groups(dev, jep106_id_groups);
+	if (ret) {
+		dev_err(dev, "sysfs create failed: %d\n", ret);
+		goto unregister_soc;
+	}
+
+	pr_info("SMCCC SoC ID: %s Revision %s\n", soc_dev_attr->soc_id,
+		soc_dev_attr->revision);
+
+	return 0;
+
+unregister_soc:
+	soc_device_unregister(soc_dev);
+free_soc:
+	kfree(soc_dev_attr);
+	return ret;
+}
+module_init(smccc_soc_init);
+
+static void __exit smccc_soc_exit(void)
+{
+	if (soc_dev)
+		soc_device_unregister(soc_dev);
+	kfree(soc_dev_attr);
+}
+module_exit(smccc_soc_exit);
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index d6b0f4acc707..04414fc2000f 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -68,6 +68,11 @@
 			   ARM_SMCCC_SMC_32,				\
 			   0, 1)
 
+#define ARM_SMCCC_ARCH_SOC_ID						\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
+			   ARM_SMCCC_SMC_32,				\
+			   0, 2)
+
 #define ARM_SMCCC_ARCH_WORKAROUND_1					\
 	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
 			   ARM_SMCCC_SMC_32,				\
-- 
2.17.1