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* [PATCH 1/1] mfd: Add I2C based System Configuaration (SYSCON) access
@ 2020-06-16 17:29 Lee Jones
  2020-06-16 18:06 ` Lee Jones
  0 siblings, 1 reply; 2+ messages in thread
From: Lee Jones @ 2020-06-16 17:29 UTC (permalink / raw)
  To: michael, robh+dt, broonie, gregkh, andriy.shevchenko, devicetree,
	linus.walleij, bgolaszewski, arnd
  Cc: Lee Jones, linux-kernel, linux-arm-kernel

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>
---
 drivers/mfd/Kconfig            |  7 +++
 drivers/mfd/Makefile           |  1 +
 drivers/mfd/syscon-i2c.c       | 89 ++++++++++++++++++++++++++++++++++
 include/linux/mfd/syscon-i2c.h | 26 ++++++++++
 4 files changed, 123 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..63ae78b92b086 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
+	bool "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..404e595d7646c
--- /dev/null
+++ b/drivers/mfd/syscon-i2c.c
@@ -0,0 +1,89 @@
+// 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/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_node *np;
+	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 *of_syscon_i2c_register(struct i2c_client *client)
+{
+	struct regmap_config syscon_config = syscon_i2c_regmap_config;
+	struct device_node *np = client->dev.of_node;
+	struct syscon *syscon;
+	struct regmap *regmap;
+	int ret;
+
+	syscon = devm_kzalloc(&client->dev, sizeof(*syscon), GFP_KERNEL);
+	if (!syscon)
+		return ERR_PTR(-ENOMEM);
+
+	syscon_config.name = of_node_full_name(np);
+
+	regmap = devm_regmap_init_i2c(client, &syscon_config);
+	if (IS_ERR(regmap)) {
+		dev_err(&client->dev, "Failed to initialise Regmap I2C\n");
+		ret = PTR_ERR(regmap);
+		return ERR_PTR(ret);
+	}
+
+	syscon->regmap = regmap;
+	syscon->np = np;
+
+	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 *i2c_device_node_get_regmap(struct i2c_client *client)
+{
+	struct device_node *np = client->dev.of_node;
+	struct syscon *entry, *syscon = NULL;
+
+	spin_lock(&syscon_i2c_list_slock);
+
+	list_for_each_entry(entry, &syscon_i2c_list, list)
+		if (entry->np == np) {
+			syscon = entry;
+			break;
+		}
+
+	spin_unlock(&syscon_i2c_list_slock);
+
+	if (!syscon)
+		syscon = of_syscon_i2c_register(client);
+
+	if (IS_ERR(syscon))
+		return ERR_CAST(syscon);
+
+	return syscon->regmap;
+}
+
+struct regmap *i2c_device_node_to_regmap(struct i2c_client *client)
+{
+	return i2c_device_node_get_regmap(client);
+}
+EXPORT_SYMBOL_GPL(i2c_device_node_to_regmap);
diff --git a/include/linux/mfd/syscon-i2c.h b/include/linux/mfd/syscon-i2c.h
new file mode 100644
index 0000000000000..854e316fec93e
--- /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>
+
+#ifdef CONFIG_MFD_SYSCON_I2C
+extern struct regmap *i2c_device_node_to_regmap(struct i2c_client *client);
+#else
+static inline struct regmap *i2c_device_node_to_regmap(struct i2c_client *client)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
+#endif
+
+#endif /* __LINUX_MFD_SYSCON_I2C_H__ */
-- 
2.25.1


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