add SAMA5D2 PIOBU GPIO driver

On SAMA5D2 SoC the PIOBU pins do not lose their voltage during Backup/Self-refresh mode. This can be useful, for example, when the voltage must remain positive for a peripheral during Backup/Self-refresh mode (suspend-to ram is the Linux equivalent state).

v4:
- readd Makefile and Kconfig changes which are missing in v3

v3:
- change driver's compatible to atmel,sama5d2-secumod
- get syscon using syscon_node_to_regmap(pdev->dev.of_node)
- document how to use SECUMOD as a gpio-controller

v2:
- make driver be a subnode of the syscon node
- change Kconfig to depend on MFD_SYSCON and select GPIO_SYSCON
- change include header from linux/gpio.h to linux/gpio/driver.h
- include linux/bits.h header
- change intrusion in comment to tamper
- fix kerneldoc of functions
- replace GPIOF_DIR_* flags with 0/1
- replace ?: statement with if-else
- remove the use of sama5d2_piobu_template_chip
- retrieve syscon via syscon_node_to_regmap(pdev->dev.parent->of_node);

Note that PIOBU_REG_SIZE is used to determine the register to write to with regmap:

	reg = PIOBU_BASE + pin * PIOBU_REG_SIZE;

Also, no irq capability implemented.

Andrei Stefanescu (2):
dt-bindings: arm: atmel: describe SECUMOD usage as a GPIO controller
gpio: add driver for SAMA5D2 PIOBU pins

 .../devicetree/bindings/arm/atmel-sysregs.txt      |  12 +-
 MAINTAINERS                                        |   6 +
 drivers/gpio/Kconfig                               |  11 +
 drivers/gpio/Makefile                              |   1 +
 drivers/gpio/gpio-sama5d2-piobu.c                  | 253 +++++++++++++++++++++
 5 files changed, 282 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpio/gpio-sama5d2-piobu.c

2.7.4

This patch describes the Security Module's usage as a GPIO controller for its PIOBU pins. These pins have the special property of maintaining their voltage during suspend-to-mem.

---
 Documentation/devicetree/bindings/arm/atmel-sysregs.txt | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

index 4b96608..c89db84 100644
@@ -158,14 +158,24 @@ Security Module (SECUMOD)
 
 The Security Module macrocell provides all necessary secure functions to avoid
 voltage, temperature, frequency and mechanical attacks on the chip. It also
-embeds secure memories that can be scrambled
+embeds secure memories that can be scrambled.
+
+The Security Module also offers the PIOBU pins which can be used as GPIO pins.
+Note that they maintain their voltage during Backup/Self-refresh. 
 
 required properties:
 - compatible: Should be "atmel,<chip>-secumod", "syscon".
   <chip> can be "sama5d2".
 - reg: Should contain registers location and length
+- gpio-controller:	Marks the port as GPIO controller.
+- #gpio-cells:		There are 2. The pin number is the
+			first, the second represents additional
+			parameters such as GPIO_ACTIVE_HIGH/LOW.
+
 
 	secumod@fc040000 {
 		compatible = "atmel,sama5d2-secumod", "syscon";
 		reg = <0xfc040000 0x100>;
+		gpio-controller;
+		#gpio-cells = <2>;
 	};

2.7.4

Patch applied with Rob's ACK.

Yours,
Linus Walleij

PIOBU pins do not lose their voltage during Backup/Self-refresh. This patch adds a simple GPIO controller for them and a maintainer for the driver.

This driver adds support for using the pins as GPIO offering the possibility to read/set the voltage.

---
 MAINTAINERS                       |   6 +
 drivers/gpio/Kconfig              |  11 ++
 drivers/gpio/Makefile             |   1 +
 drivers/gpio/gpio-sama5d2-piobu.c | 253 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 271 insertions(+)
 create mode 100644 drivers/gpio/gpio-sama5d2-piobu.c

index f485597..fadc96d 100644
@@ -9760,6 +9760,12 @@ M:	Nicolas Ferre <[email protected]>
 S:	Supported
 F:	drivers/power/reset/at91-sama5d2_shdwc.c
 
+MICROCHIP SAMA5D2-COMPATIBLE PIOBU GPIO
+M:	Andrei Stefanescu <[email protected]>
+L:	[email protected] (moderated for non-subscribers)
+L:	[email protected]
+F:	drivers/gpio/gpio-sama5d2-piobu.c
+
 MICROCHIP SPI DRIVER
 M:	Nicolas Ferre <[email protected]>
 S:	Supported

index 833a1b5..1c41fac 100644
@@ -429,6 +429,17 @@ config GPIO_REG
 	  A 32-bit single register GPIO fixed in/out implementation.  This
 	  can be used to represent any register as a set of GPIO signals.
 
+config GPIO_SAMA5D2_PIOBU
+	tristate "SAMA5D2 PIOBU GPIO support"
+	depends on MFD_SYSCON
+	select GPIO_SYSCON
+	help
+	  Say yes here to use the PIOBU pins as GPIOs.
+
+	  PIOBU pins on the SAMA5D2 can be used as GPIOs.
+	  The difference from regular GPIOs is that they
+	  maintain their value during backup/self-refresh.
+
 config GPIO_SIOX
 	tristate "SIOX GPIO support"
 	depends on SIOX

index 671c447..f18d345 100644
@@ -108,6 +108,7 @@ obj-$(CONFIG_GPIO_RDC321X)	+= gpio-rdc321x.o
 obj-$(CONFIG_GPIO_RCAR)		+= gpio-rcar.o
 obj-$(CONFIG_GPIO_REG)		+= gpio-reg.o
 obj-$(CONFIG_ARCH_SA1100)	+= gpio-sa1100.o
+obj-$(CONFIG_GPIO_SAMA5D2_PIOBU)	+= gpio-sama5d2-piobu.o
 obj-$(CONFIG_GPIO_SCH)		+= gpio-sch.o
 obj-$(CONFIG_GPIO_SCH311X)	+= gpio-sch311x.o
 obj-$(CONFIG_GPIO_SNPS_CREG)	+= gpio-creg-snps.o

2.7.4

Patch applied for v4.21, sorry for taking so long to reply!

Good work on this driver Andrei, it looks really nice now.

Yours,
Linus Walleij