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.

Partial support UP boards:
* UP core + CREX
* UP core + CRST02

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

drivers/leds/Kconfig

@@ -872,6 +872,16 @@ source "drivers/leds/flash/Kconfig"
 comment "RGB LED drivers"
 source "drivers/leds/rgb/Kconfig"
 
+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. The UP boards come
+	  with a few FPGA-controlled onboard LEDs. The UP Squared includes 4 LEDs
+	  (yellow, green, red and blue) on the underside of the board which are
+	  controlled by the pin control FPGA on the board
+
 comment "LED Triggers"
 source "drivers/leds/trigger/Kconfig"
 

drivers/leds/Makefile

@@ -83,6 +83,7 @@ obj-$(CONFIG_LEDS_TI_LMU_COMMON)	+= leds-ti-lmu-common.o
 obj-$(CONFIG_LEDS_TLC591XX)		+= leds-tlc591xx.o
 obj-$(CONFIG_LEDS_TPS6105X)		+= leds-tps6105x.o
 obj-$(CONFIG_LEDS_TURRIS_OMNIA)		+= leds-turris-omnia.o
+obj-$(CONFIG_LEDS_UPBOARD)		+= leds-upboard.o
 obj-$(CONFIG_LEDS_WM831X_STATUS)	+= leds-wm831x-status.o
 obj-$(CONFIG_LEDS_WM8350)		+= leds-wm8350.o
 obj-$(CONFIG_LEDS_WRAP)			+= leds-wrap.o

drivers/leds/leds-upboard.c

@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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

@@ -2104,6 +2104,15 @@ config MFD_QCOM_PM8008
 	  under it in the device tree. Additional drivers must be enabled in
 	  order to use the functionality of the device.
 
+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. The UP
+	  board 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.
+
 menu "Multimedia Capabilities Port drivers"
 	depends on ARCH_SA1100
 

drivers/mfd/Makefile

@@ -250,6 +250,7 @@ obj-$(CONFIG_MFD_ALTERA_A10SR)	+= altera-a10sr.o
 obj-$(CONFIG_MFD_ALTERA_SYSMGR) += altera-sysmgr.o
 obj-$(CONFIG_MFD_STPMIC1)	+= stpmic1.o
 obj-$(CONFIG_MFD_SUN4I_GPADC)	+= sun4i-gpadc.o
+obj-$(CONFIG_MFD_UPBOARD_FPGA)	+= upboard-fpga.o
 
 obj-$(CONFIG_MFD_STM32_LPTIMER)	+= stm32-lptimer.o
 obj-$(CONFIG_MFD_STM32_TIMERS) 	+= stm32-timers.o