Add initial support for the Actions Semi ATC260x PMICs which integrates
Audio Codec, Power management, Clock generation and GPIO controller
blocks.

For the moment this driver only supports Regulator, Poweroff and Onkey
functionalities for the ATC2603C and ATC2609A chip variants.

Since the PMICs can be accessed using both I2C and SPI buses, the
following driver structure has been adopted:

           -----> atc260x-core.c (Implements core functionalities)
          /
ATC260x --------> atc260x-i2c.c (Implements I2C interface)
          \
           -----> atc260x-spi.c (Implements SPI interface - TODO)

Co-developed-by: Manivannan Sadhasivam <redacted>
Signed-off-by: Manivannan Sadhasivam <redacted>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
---
Changes in v6 - per Lee's feedback:
- Added ATC260X_CHIP_REV_MAX magic number
- Fixed code formattting arround atc260x_i2c_driver initialization
- Replaced dev_init() callback in struct atc260x with a pointer to a new struct
atc260x_init_regs to hold hardware specific registry information
- Added a generic atc260x_dev_init() function and instantiated atc2603c_init_regs
and atc2609a_init_regs

Changes in v5:
 - None

Changes in v4 - according to Lee's review:
 - Replaced 'regmap_add_irq_chip()' with 'devm' counterpart and dropped
   'atc260x_device_remove()' and 'atc260x_i2c_remove()' functions
 - Moved kerneldoc sections from prototypes to real functions
 - Placed single line entries on one line for mfd_cells[]
 - Several other minor changes

Changes in v3:
 - Fixed the issues reported by Lee's kernel test robot:
   WARNING: modpost: missing MODULE_LICENSE() in drivers/mfd/atc260x-core.o
   >> FATAL: modpost: drivers/mfd/atc260x-i2c: sizeof(struct i2c_device_id)=24 is
      not a modulo of the size of section __mod_i2c__<identifier>_device_table=588.
   >> Fix definition of struct i2c_device_id in mod_devicetable.h
 - Dropped the usage of '.of_compatible' fields in {atc2603c,atc2609a}_mfd_cells[]
 - Added 'Co-developed-by' tag in commit message and dropped [cristian: ...] line

 drivers/mfd/Kconfig                  |  18 ++
 drivers/mfd/Makefile                 |   3 +
 drivers/mfd/atc260x-core.c           | 310 +++++++++++++++++++++++++++
 drivers/mfd/atc260x-i2c.c            |  64 ++++++
 include/linux/mfd/atc260x/atc2603c.h | 281 ++++++++++++++++++++++++
 include/linux/mfd/atc260x/atc2609a.h | 308 ++++++++++++++++++++++++++
 include/linux/mfd/atc260x/core.h     |  58 +++++
 7 files changed, 1042 insertions(+)
 create mode 100644 drivers/mfd/atc260x-core.c
 create mode 100644 drivers/mfd/atc260x-i2c.c
 create mode 100644 include/linux/mfd/atc260x/atc2603c.h
 create mode 100644 include/linux/mfd/atc260x/atc2609a.h
 create mode 100644 include/linux/mfd/atc260x/core.h

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index bdfce7b15621..a27ff2e83e7a 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig

@@ -2064,6 +2064,24 @@ config MFD_WCD934X
 	  This driver provides common support WCD934x audio codec and its
 	  associated Pin Controller, Soundwire Controller and Audio codec.
 
+config MFD_ATC260X
+	tristate
+	select MFD_CORE
+	select REGMAP
+	select REGMAP_IRQ
+
+config MFD_ATC260X_I2C
+	tristate "Actions Semi ATC260x PMICs with I2C"
+	select MFD_ATC260X
+	select REGMAP_I2C
+	depends on I2C
+	help
+	  Support for the Actions Semi ATC260x PMICs controlled via I2C.
+
+	  This driver provides common support for accessing the ATC2603C
+	  and ATC2609A chip variants, additional drivers must be enabled
+	  in order to use the functionality of the device.
+
 config MFD_KHADAS_MCU
 	tristate "Support for Khadas System control Microcontroller"
 	depends on I2C

diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 14fdb188af02..1ea88d2c83b4 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile

@@ -268,3 +268,6 @@ obj-$(CONFIG_MFD_KHADAS_MCU) 	+= khadas-mcu.o
 obj-$(CONFIG_SGI_MFD_IOC3)	+= ioc3.o
 obj-$(CONFIG_MFD_SIMPLE_MFD_I2C)	+= simple-mfd-i2c.o
 obj-$(CONFIG_MFD_INTEL_M10_BMC)   += intel-m10-bmc.o
+
+obj-$(CONFIG_MFD_ATC260X)	+= atc260x-core.o
+obj-$(CONFIG_MFD_ATC260X_I2C)	+= atc260x-i2c.o

diff --git a/drivers/mfd/atc260x-core.c b/drivers/mfd/atc260x-core.c
new file mode 100644
index 000000000000..7148ff5b05b1
--- /dev/null
+++ b/drivers/mfd/atc260x-core.c

@@ -0,0 +1,310 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Core support for ATC260x PMICs
+ *
+ * Copyright (C) 2019 Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
+ * Copyright (C) 2020 Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
+ */
+
+#include <linux/interrupt.h>
+#include <linux/mfd/atc260x/core.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+
+#define ATC260X_CHIP_REV_MAX	31
+
+struct atc260x_init_regs {
+	unsigned int cmu_devrst;
+	unsigned int cmu_devrst_ints;
+	unsigned int ints_msk;
+	unsigned int pad_en;
+	unsigned int pad_en_extirq;
+};
+
+static void regmap_lock_mutex(void *__mutex)
+{
+	struct mutex *mutex = __mutex;
+
+	/*
+	 * Using regmap within an atomic context (e.g. accessing a PMIC when
+	 * powering system down) is normally allowed only if the regmap type
+	 * is MMIO and the regcache type is either REGCACHE_NONE or
+	 * REGCACHE_FLAT. For slow buses like I2C and SPI, the regmap is
+	 * internally protected by a mutex which is acquired non-atomically.
+	 *
+	 * Let's improve this by using a customized locking scheme inspired
+	 * from I2C atomic transfer. See i2c_in_atomic_xfer_mode() for a
+	 * starting point.
+	 */
+	if (system_state > SYSTEM_RUNNING && irqs_disabled())
+		mutex_trylock(mutex);
+	else
+		mutex_lock(mutex);
+}