[PATCH v5 2/4] mfd: smpro-mfd: Adds Ampere's Altra SMpro MFD driver

[Quan Nguyen <quan@os.amperecomputing.com>]

Adds Multi-function devices driver for SMpro co-processor found on the
Mt.Jade hardware reference platform with Ampere's Altra processor family.

Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
---
Changes in v5: 
  + Dropped the use of simple-mfd-i2c driver [Quan]
  + Introduced drivers/mfd/smpro-mfd.c driver to instantiate
  sub-devices. This is to avoid DT nodes without resource issue [Quan]
  + Revised commit message [Quan]

Changes in v4:
  + Add "depends on I2C" to fix build issue found by kernel test
  robot [Guenter]

Changes in v3:
  + None

Changes in v2:
  + Used 'struct of_device_id's .data attribute [Lee Jones]

 drivers/mfd/Kconfig     | 12 +++++++
 drivers/mfd/Makefile    |  1 +
 drivers/mfd/smpro-mfd.c | 74 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+)
 create mode 100644 drivers/mfd/smpro-mfd.c

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 6a3fd2d75f96..25e502cca32f 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -77,6 +77,18 @@ config MFD_AS3711
 	help
 	  Support for the AS3711 PMIC from AMS
 
+config MFD_SMPRO
+	tristate "Ampere Computing MFD SMpro core driver"
+	depends on I2C
+	select MFD_CORE
+	select REGMAP_I2C
+	help
+	  Say yes here to enable SMpro driver support for Ampere's Altra
+	  processor family.
+
+	  Ampere's Altra SMpro exposes an I2C regmap interface that can
+	  be accessed by child devices.
+
 config MFD_AS3722
 	tristate "ams AS3722 Power Management IC"
 	select MFD_CORE
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 8116c19d5fd4..046fd36de85a 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -268,6 +268,7 @@ obj-$(CONFIG_MFD_QCOM_PM8008)	+= qcom-pm8008.o
 
 obj-$(CONFIG_SGI_MFD_IOC3)	+= ioc3.o
 obj-$(CONFIG_MFD_SIMPLE_MFD_I2C)	+= simple-mfd-i2c.o
+obj-$(CONFIG_MFD_SMPRO)		+= smpro-mfd.o
 obj-$(CONFIG_MFD_INTEL_M10_BMC)   += intel-m10-bmc.o
 
 obj-$(CONFIG_MFD_ATC260X)	+= atc260x-core.o
diff --git a/drivers/mfd/smpro-mfd.c b/drivers/mfd/smpro-mfd.c
new file mode 100644
index 000000000000..b0cd3c248507
--- /dev/null
+++ b/drivers/mfd/smpro-mfd.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Ampere Altra Family SMPro MFD - I2C
+ *
+ * Copyright (c) 2021, Ampere Computing LLC
+ *
+ * Author: Quan Nguyen <quan@os.amperecomputing..com>
+ */
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/mfd/core.h>
+#include <linux/regmap.h>
+
+/* Identification Registers */
+#define MANUFACTURER_ID_REG     0x02
+#define AMPERE_MANUFACTURER_ID  0xCD3A
+
+static const struct regmap_config simple_word_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+};
+
+static const struct mfd_cell smpro_devs[] = {
+	MFD_CELL_NAME("smpro-hwmon"),
+};
+
+static int smpro_mfd_probe(struct i2c_client *i2c)
+{
+	const struct regmap_config *config;
+	struct regmap *regmap;
+	unsigned int val;
+	int ret;
+
+	config = device_get_match_data(&i2c->dev);
+	if (!config)
+		config = &simple_word_regmap_config;
+
+	regmap = devm_regmap_init_i2c(i2c, config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	/* Check for valid ID */
+	ret = regmap_read(regmap, MANUFACTURER_ID_REG, &val);
+	if (ret)
+		return ret;
+
+	if (val != AMPERE_MANUFACTURER_ID)
+		return -ENODEV;
+
+	return devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_AUTO,
+				    smpro_devs, ARRAY_SIZE(smpro_devs), NULL, 0, NULL);
+}
+
+static const struct of_device_id smpro_mfd_of_match[] = {
+	{ .compatible = "ampere,smpro", .data = &simple_word_regmap_config },
+	{}
+};
+MODULE_DEVICE_TABLE(of, smpro_mfd_of_match);
+
+static struct i2c_driver smpro_mfd_driver = {
+	.probe_new = smpro_mfd_probe,
+	.driver = {
+		.name = "smpro-mfd-i2c",
+		.of_match_table = smpro_mfd_of_match,
+	},
+};
+module_i2c_driver(smpro_mfd_driver);
+
+MODULE_AUTHOR("Quan Nguyen <quan@os.amperecomputing.com>");
+MODULE_DESCRIPTION("SMPRO MFD - I2C driver");
+MODULE_LICENSE("GPL v2");
-- 
2.28.0