mfd: Add support for UP board CPLD/FPGA

The UP Squared board <http://www.upboard.com> implements certain
features (pin control, onboard LEDs or CEC) through an on-board FPGA.

This mfd driver implements the line protocol to read and write registers
from the FPGA through regmap. The register address map is also included.

The UP boards come with a few FPGA-controlled onboard LEDs:
* UP Board: yellow, green, red
* UP Squared: blue, yellow, green, red

The UP Boards provide a few I/O pin headers (for both GPIO and
functions), including a 40-pin Raspberry Pi compatible header.

This patch implements support for the FPGA-based pin controller that
manages direction and enable state for those header pins.

Signed-off-by: Javier Arteaga <javier@emutex.com>
[merge various fixes]
Signed-off-by: Nicola Lunghi <nicola.lunghi@emutex.com>

arch/x86/configs/upboard_defconfig

@@ -1636,6 +1636,7 @@ CONFIG_SPI_SPIDEV=m
 CONFIG_SPI_LOOPBACK_TEST=m
 CONFIG_PPS_CLIENT_LDISC=m
 CONFIG_PPS_CLIENT_PARPORT=m
+CONFIG_PINCTRL_UPBOARD=m
 CONFIG_PINCTRL_BAYTRAIL=y
 CONFIG_PINCTRL_CHERRYVIEW=y
 CONFIG_PINCTRL_BROXTON=y
@@ -1864,6 +1865,7 @@ CONFIG_MFD_MENF21BMC=m
 CONFIG_MFD_VIPERBOARD=m
 CONFIG_MFD_RTSX_PCI=m
 CONFIG_MFD_RTSX_USB=m
+CONFIG_MFD_UPBOARD_FPGA=m
 CONFIG_MEDIA_SUPPORT=m
 CONFIG_MEDIA_CAMERA_SUPPORT=y
 CONFIG_MEDIA_ANALOG_TV_SUPPORT=y
@@ -2613,6 +2615,7 @@ CONFIG_LEDS_IS31FL319X=m
 CONFIG_LEDS_IS31FL32XX=m
 CONFIG_LEDS_BLINKM=m
 CONFIG_LEDS_MLXCPLD=m
+CONFIG_LEDS_UPBOARD=m
 CONFIG_LEDS_TRIGGER_TIMER=m
 CONFIG_LEDS_TRIGGER_ONESHOT=m
 CONFIG_LEDS_TRIGGER_DISK=y

drivers/leds/Kconfig

@@ -659,6 +659,13 @@ config LEDS_MLXCPLD
 	  This option enabled support for the LEDs on the Mellanox
 	  boards. Say Y to enabled these.
 
+config LEDS_UPBOARD
+	tristate "LED support for the UP board"
+	depends on LEDS_CLASS
+	depends on MFD_UPBOARD_FPGA
+	help
+	  This option enables support for the UP board LEDs.
+
 comment "LED Triggers"
 source "drivers/leds/trigger/Kconfig"
 

drivers/leds/Makefile

@@ -71,6 +71,7 @@ obj-$(CONFIG_LEDS_IS31FL319X)		+= leds-is31fl319x.o
 obj-$(CONFIG_LEDS_IS31FL32XX)		+= leds-is31fl32xx.o
 obj-$(CONFIG_LEDS_PM8058)		+= leds-pm8058.o
 obj-$(CONFIG_LEDS_MLXCPLD)		+= leds-mlxcpld.o
+obj-$(CONFIG_LEDS_UPBOARD)		+= leds-upboard.o
 
 # LED SPI Drivers
 obj-$(CONFIG_LEDS_DAC124S085)		+= leds-dac124s085.o

drivers/leds/leds-upboard.c

@@ -0,0 +1,88 @@
+/*
+ * UP Board FPGA-based LED driver
+ *
+ * Copyright (c) 2017, Emutex Ltd. All rights reserved.
+ *
+ * Author: Javier Arteaga <javier@emutex.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/leds.h>
+#include <linux/mfd/upboard-fpga.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+struct upboard_led {
+	struct regmap_field *field;
+	struct led_classdev cdev;
+};
+
+static enum led_brightness upboard_led_brightness_get(struct led_classdev
+						      *cdev)
+{
+	struct upboard_led *led = container_of(cdev, struct upboard_led, cdev);
+	int brightness = 0;
+
+	regmap_field_read(led->field, &brightness);
+
+	return brightness;
+};
+
+static void upboard_led_brightness_set(struct led_classdev *cdev,
+				       enum led_brightness brightness)
+{
+	struct upboard_led *led = container_of(cdev, struct upboard_led, cdev);
+
+	regmap_field_write(led->field, brightness != LED_OFF);
+};
+
+static int __init upboard_led_probe(struct platform_device *pdev)
+{
+	struct upboard_fpga * const fpga = dev_get_drvdata(pdev->dev.parent);
+	struct reg_field fldconf = {
+		.reg = UPFPGA_REG_FUNC_EN0,
+	};
+	struct upboard_led_data * const pdata = pdev->dev.platform_data;
+	struct upboard_led *led;
+
+	if (!fpga || !pdata)
+		return -EINVAL;
+
+	led = devm_kzalloc(&pdev->dev, sizeof(*led), GFP_KERNEL);
+	if (!led)
+		return -ENOMEM;
+
+	fldconf.lsb = pdata->bit;
+	fldconf.msb = pdata->bit;
+	led->field = devm_regmap_field_alloc(&pdev->dev, fpga->regmap, fldconf);
+	if (IS_ERR(led->field))
+		return PTR_ERR(led->field);
+
+	led->cdev.brightness_get = upboard_led_brightness_get;
+	led->cdev.brightness_set = upboard_led_brightness_set;
+	led->cdev.name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "upboard:%s:",
+					pdata->colour);
+
+	if (!led->cdev.name)
+		return -ENOMEM;
+
+	return devm_led_classdev_register(&pdev->dev, &led->cdev);
+};
+
+static struct platform_driver upboard_led_driver = {
+	.driver = {
+		.name = "upboard-led",
+	},
+};
+
+module_platform_driver_probe(upboard_led_driver, upboard_led_probe);
+
+MODULE_AUTHOR("Javier Arteaga <javier@emutex.com>");
+MODULE_DESCRIPTION("UP Board LED driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:upboard-led");

drivers/mfd/Kconfig

@@ -1607,6 +1607,12 @@ config MFD_STW481X
 	  in various ST Microelectronics and ST-Ericsson embedded
 	  Nomadik series.
 
+config MFD_UPBOARD_FPGA
+	tristate "Support for the UP board FPGA"
+	select MFD_CORE
+	help
+	  Select this option to enable the UP and UP^2 on-board FPGA.
+
 menu "Multimedia Capabilities Port drivers"
 	depends on ARCH_SA1100
 

drivers/mfd/Makefile

@@ -212,3 +212,5 @@ obj-$(CONFIG_MFD_MT6397)	+= mt6397-core.o
 obj-$(CONFIG_MFD_INTEL_VUPORT)	+= intel-vuport.o
 
 obj-$(CONFIG_MFD_ALTERA_A10SR)	+= altera-a10sr.o
+
+obj-$(CONFIG_MFD_UPBOARD_FPGA)  += upboard-fpga.o