[PATCH v3 1/1] mfd: Add I2C based System Configuaration (SYSCON) access

Lee Jones
2020-06-18T08:04:14Z

The existing SYSCON implementation only supports MMIO (memory mapped)
accesses, facilitated by Regmap. This extends support for registers
held behind I2C busses.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
Changelog:

v2 => v3
- Change 'is CONFIG' present check to include loadable modules
- s/#ifdef CONFIG_MFD_SYSCON_I2C/#if IS_ENABLED(CONFIG_MFD_SYSCON_I2C)/

v1 => v2
- Remove legacy references to OF
- Allow building as a module (fixes h8300 0-day issue)

drivers/mfd/Kconfig | 7 +++
drivers/mfd/Makefile | 1 +
drivers/mfd/syscon-i2c.c | 90 ++++++++++++++++++++++++++++++++++
include/linux/mfd/syscon-i2c.h | 26 ++++++++++
4 files changed, 124 insertions(+)
create mode 100644 drivers/mfd/syscon-i2c.c
create mode 100644 include/linux/mfd/syscon-i2c.h

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 0a59249198d34..f25f80f68edca 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1300,6 +1300,13 @@ config MFD_SYSCON
Select this option to enable accessing system control registers
via regmap.

+config MFD_SYSCON_I2C
+ tristate "System Controller Register R/W Based on I2C Regmap"
+ select REGMAP_I2C
+ help
+ Select this option to enable accessing system control registers
+ via I2C using regmap.
+
config MFD_DAVINCI_VOICECODEC
tristate
select MFD_CORE
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index f935d10cbf0fc..0aec1f42ac979 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -219,6 +219,7 @@ obj-$(CONFIG_MFD_RK808) += rk808.o
obj-$(CONFIG_MFD_RN5T618) += rn5t618.o
obj-$(CONFIG_MFD_SEC_CORE) += sec-core.o sec-irq.o
obj-$(CONFIG_MFD_SYSCON) += syscon.o
+obj-$(CONFIG_MFD_SYSCON_I2C) += syscon-i2c.o
obj-$(CONFIG_MFD_LM3533) += lm3533-core.o lm3533-ctrlbank.o
obj-$(CONFIG_MFD_VEXPRESS_SYSREG) += vexpress-sysreg.o
obj-$(CONFIG_MFD_RETU) += retu-mfd.o
diff --git a/drivers/mfd/syscon-i2c.c b/drivers/mfd/syscon-i2c.c
new file mode 100644
index 0000000000000..be20ff45ece07
--- /dev/null
+++ b/drivers/mfd/syscon-i2c.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * System Control Driver accessed over I2C
+ *
+ * Copyright (C) 2020 Linaro Ltd.
+ *
+ * Author: Lee Jones <lee.jones@linaro.org>
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/list.h>
+#include <linux/mfd/syscon-i2c.h>
+#include <linux/regmap.h>
+
+static DEFINE_SPINLOCK(syscon_i2c_list_slock);
+static LIST_HEAD(syscon_i2c_list);
+
+struct syscon {
+ struct device *dev;
+ struct regmap *regmap;
+ struct list_head list;
+};
+
+static const struct regmap_config syscon_i2c_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+};
+
+static struct syscon *syscon_i2c_register(struct i2c_client *client)
+{
+ struct regmap_config syscon_config = syscon_i2c_regmap_config;
+ struct device *dev = &client->dev;
+ struct syscon *syscon;
+ struct regmap *regmap;
+ int ret;
+
+ syscon = devm_kzalloc(dev, sizeof(*syscon), GFP_KERNEL);
+ if (!syscon)
+ return ERR_PTR(-ENOMEM);
+
+ syscon_config.name = dev_name(dev);
+
+ regmap = devm_regmap_init_i2c(client, &syscon_config);
+ if (IS_ERR(regmap)) {
+ dev_err(dev, "Failed to initialise Regmap I2C\n");
+ ret = PTR_ERR(regmap);
+ return ERR_PTR(ret);
+ }
+
+ syscon->regmap = regmap;
+ syscon->dev = dev;
+
+ spin_lock(&syscon_i2c_list_slock);
+ list_add_tail(&syscon->list, &syscon_i2c_list);
+ spin_unlock(&syscon_i2c_list_slock);
+
+ return syscon;
+}
+
+static struct regmap *syscon_i2c_get_regmap(struct i2c_client *client)
+{
+ struct device *dev = &client->dev;
+ struct syscon *entry, *syscon = NULL;
+
+ spin_lock(&syscon_i2c_list_slock);
+
+ list_for_each_entry(entry, &syscon_i2c_list, list)
+ if (entry->dev == dev) {
+ syscon = entry;
+ break;
+ }
+
+ spin_unlock(&syscon_i2c_list_slock);
+
+ if (!syscon)
+ syscon = syscon_i2c_register(client);
+
+ if (IS_ERR(syscon))
+ return ERR_CAST(syscon);
+
+ return syscon->regmap;
+}
+
+struct regmap *syscon_i2c_to_regmap(struct i2c_client *client)
+{
+ return syscon_i2c_get_regmap(client);
+}
+EXPORT_SYMBOL_GPL(syscon_i2c_to_regmap);
diff --git a/include/linux/mfd/syscon-i2c.h b/include/linux/mfd/syscon-i2c.h
new file mode 100644
index 0000000000000..490bc37b603cb
--- /dev/null
+++ b/include/linux/mfd/syscon-i2c.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * System Control Driver accessed via I2C
+ *
+ * Copyright (C) 2020 Linaro Ltd.
+ *
+ * Author: Lee Jones <lee.jones@linaro.org>
+ */
+
+#ifndef __LINUX_MFD_SYSCON_I2C_H__
+#define __LINUX_MFD_SYSCON_I2C_H__
+
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+
+#if IS_ENABLED(CONFIG_MFD_SYSCON_I2C)
+extern struct regmap *syscon_i2c_to_regmap(struct i2c_client *client);
+#else
+static inline struct regmap *syscon_i2c_to_regmap(struct i2c_client *client)
+{
+ return ERR_PTR(-ENOTSUPP);
+}
+#endif
+
+#endif /* __LINUX_MFD_SYSCON_I2C_H__ */
--
2.25.1