Input: add new sun4i-lradc-keys driver

Allwinnner sunxi SoCs have a low resolution adc (called lradc) which is
specifically designed to have various (tablet) keys (ie home, back, search,
etc). attached to it using a resistor network. This adds a driver for this.

There are 2 channels, currently this driver only supports chan0 since there
are no boards known to use chan1.

This has been tested on an olimex a10s-olinuxino-micro, a13-olinuxino, and
a20-olinuxino-micro.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

3 files changed, 297 insertions, 0 deletions

diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
index a5d9b3f3c871..a89ba7cb96f1 100644
--- a/drivers/input/keyboard/Kconfig
+++ b/drivers/input/keyboard/Kconfig
@@ -568,6 +568,16 @@ config KEYBOARD_STMPE
           To compile this driver as a module, choose M here: the module will be
           called stmpe-keypad.
 
+config KEYBOARD_SUN4I_LRADC
+        tristate "Allwinner sun4i low res adc attached tablet keys support"
+        depends on ARCH_SUNXI
+        help
+          This selects support for the Allwinner low res adc attached tablet
+          keys found on Allwinner sunxi SoCs.
+
+          To compile this driver as a module, choose M here: the
+          module will be called sun4i-lradc-keys.
+
 config KEYBOARD_DAVINCI
         tristate "TI DaVinci Key Scan"
         depends on ARCH_DAVINCI_DM365
diff --git a/drivers/input/keyboard/Makefile b/drivers/input/keyboard/Makefile
index febafa527eb6..470767884bd8 100644
--- a/drivers/input/keyboard/Makefile
+++ b/drivers/input/keyboard/Makefile
@@ -53,6 +53,7 @@ obj-$(CONFIG_KEYBOARD_SPEAR)		+= spear-keyboard.o
 obj-$(CONFIG_KEYBOARD_STMPE)            += stmpe-keypad.o
 obj-$(CONFIG_KEYBOARD_STOWAWAY)         += stowaway.o
 obj-$(CONFIG_KEYBOARD_ST_KEYSCAN)       += st-keyscan.o
+obj-$(CONFIG_KEYBOARD_SUN4I_LRADC)      += sun4i-lradc-keys.o
 obj-$(CONFIG_KEYBOARD_SUNKBD)           += sunkbd.o
 obj-$(CONFIG_KEYBOARD_TC3589X)          += tc3589x-keypad.o
 obj-$(CONFIG_KEYBOARD_TEGRA)            += tegra-kbc.o
diff --git a/drivers/input/keyboard/sun4i-lradc-keys.c b/drivers/input/keyboard/sun4i-lradc-keys.c
new file mode 100644
index 000000000000..cc8f7ddcee53
--- /dev/null
+++ b/drivers/input/keyboard/sun4i-lradc-keys.c
@@ -0,0 +1,286 @@
+/*
+ * Allwinner sun4i low res adc attached tablet keys driver
+ *
+ * Copyright (C) 2014 Hans de Goede <hdegoede@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+/*
+ * Allwinnner sunxi SoCs have a lradc which is specifically designed to have
+ * various (tablet) keys (ie home, back, search, etc). attached to it using
+ * a resistor network. This driver is for the keys on such boards.
+ *
+ * There are 2 channels, currently this driver only supports channel 0 since
+ * there are no boards known to use channel 1.
+ */
+
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#define LRADC_CTRL              0x00
+#define LRADC_INTC              0x04
+#define LRADC_INTS              0x08
+#define LRADC_DATA0             0x0c
+#define LRADC_DATA1             0x10
+
+/* LRADC_CTRL bits */
+#define FIRST_CONVERT_DLY(x)    ((x) << 24) /* 8 bits */
+#define CHAN_SELECT(x)          ((x) << 22) /* 2 bits */
+#define CONTINUE_TIME_SEL(x)    ((x) << 16) /* 4 bits */
+#define KEY_MODE_SEL(x)         ((x) << 12) /* 2 bits */
+#define LEVELA_B_CNT(x)         ((x) << 8)  /* 4 bits */
+#define HOLD_EN(x)              ((x) << 6)
+#define LEVELB_VOL(x)           ((x) << 4)  /* 2 bits */
+#define SAMPLE_RATE(x)          ((x) << 2)  /* 2 bits */
+#define ENABLE(x)               ((x) << 0)
+
+/* LRADC_INTC and LRADC_INTS bits */
+#define CHAN1_KEYUP_IRQ         BIT(12)
+#define CHAN1_ALRDY_HOLD_IRQ    BIT(11)
+#define CHAN1_HOLD_IRQ          BIT(10)
+#define CHAN1_KEYDOWN_IRQ       BIT(9)
+#define CHAN1_DATA_IRQ          BIT(8)
+#define CHAN0_KEYUP_IRQ         BIT(4)
+#define CHAN0_ALRDY_HOLD_IRQ    BIT(3)
+#define CHAN0_HOLD_IRQ          BIT(2)
+#define CHAN0_KEYDOWN_IRQ       BIT(1)
+#define CHAN0_DATA_IRQ          BIT(0)
+
+struct sun4i_lradc_keymap {
+        u32 voltage;
+        u32 keycode;
+};
+
+struct sun4i_lradc_data {
+        struct device *dev;
+        struct input_dev *input;
+        void __iomem *base;
+        struct regulator *vref_supply;
+        struct sun4i_lradc_keymap *chan0_map;
+        u32 chan0_map_count;
+        u32 chan0_keycode;
+        u32 vref;
+};
+
+static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
+{
+        struct sun4i_lradc_data *lradc = dev_id;
+        u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
+
+        ints  = readl(lradc->base + LRADC_INTS);
+
+        /*
+         * lradc supports only one keypress at a time, release does not give
+         * any info as to which key was released, so we cache the keycode.
+         */
+
+        if (ints & CHAN0_KEYUP_IRQ) {
+                input_report_key(lradc->input, lradc->chan0_keycode, 0);
+                lradc->chan0_keycode = 0;
+        }
+
+        if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
+                val = readl(lradc->base + LRADC_DATA0) & 0x3f;
+                voltage = val * lradc->vref / 63;
+
+                for (i = 0; i < lradc->chan0_map_count; i++) {
+                        diff = abs(lradc->chan0_map[i].voltage - voltage);
+                        if (diff < closest) {
+                                closest = diff;
+                                keycode = lradc->chan0_map[i].keycode;
+                        }
+                }
+
+                lradc->chan0_keycode = keycode;
+                input_report_key(lradc->input, lradc->chan0_keycode, 1);
+        }
+
+        input_sync(lradc->input);
+
+        writel(ints, lradc->base + LRADC_INTS);
+
+        return IRQ_HANDLED;
+}
+
+static int sun4i_lradc_open(struct input_dev *dev)
+{
+        struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
+        int error;
+
+        error = regulator_enable(lradc->vref_supply);
+        if (error)
+                return error;
+
+        /* lradc Vref internally is divided by 2/3 */
+        lradc->vref = regulator_get_voltage(lradc->vref_supply) * 2 / 3;
+
+        /*
+         * Set sample time to 4 ms / 250 Hz. Wait 2 * 4 ms for key to
+         * stabilize on press, wait (1 + 1) * 4 ms for key release
+         */
+        writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
+                SAMPLE_RATE(0) | ENABLE(1), lradc->base + LRADC_CTRL);
+
+        writel(CHAN0_KEYUP_IRQ | CHAN0_KEYDOWN_IRQ, lradc->base + LRADC_INTC);
+
+        return 0;
+}
+
+static void sun4i_lradc_close(struct input_dev *dev)
+{
+        struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
+
+        /* Disable lradc, leave other settings unchanged */
+        writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
+                SAMPLE_RATE(2), lradc->base + LRADC_CTRL);
+        writel(0, lradc->base + LRADC_INTC);
+
+        regulator_disable(lradc->vref_supply);
+}
+
+static int sun4i_lradc_load_dt_keymap(struct device *dev,
+                                      struct sun4i_lradc_data *lradc)
+{
+        struct device_node *np, *pp;
+        int i;
+        int error;
+
+        np = dev->of_node;
+        if (!np)
+                return -EINVAL;
+
+        lradc->chan0_map_count = of_get_child_count(np);
+        if (lradc->chan0_map_count == 0) {
+                dev_err(dev, "keymap is missing in device tree\n");
+                return -EINVAL;
+        }
+
+        lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,
+                                              sizeof(struct sun4i_lradc_keymap),
+                                              GFP_KERNEL);
+        if (!lradc->chan0_map)
+                return -ENOMEM;
+
+        i = 0;
+        for_each_child_of_node(np, pp) {
+                struct sun4i_lradc_keymap *map = &lradc->chan0_map[i];
+                u32 channel;
+
+                error = of_property_read_u32(pp, "channel", &channel);
+                if (error || channel != 0) {
+                        dev_err(dev, "%s: Inval channel prop\n", pp->name);
+                        return -EINVAL;
+                }
+
+                error = of_property_read_u32(pp, "voltage", &map->voltage);
+                if (error) {
+                        dev_err(dev, "%s: Inval voltage prop\n", pp->name);
+                        return -EINVAL;
+                }
+
+                error = of_property_read_u32(pp, "linux,code", &map->keycode);
+                if (error) {
+                        dev_err(dev, "%s: Inval linux,code prop\n", pp->name);
+                        return -EINVAL;
+                }
+
+                i++;
+        }
+
+        return 0;
+}
+
+static int sun4i_lradc_probe(struct platform_device *pdev)
+{
+        struct sun4i_lradc_data *lradc;
+        struct device *dev = &pdev->dev;
+        int i;
+        int error;
+
+        lradc = devm_kzalloc(dev, sizeof(struct sun4i_lradc_data), GFP_KERNEL);
+        if (!lradc)
+                return -ENOMEM;
+
+        error = sun4i_lradc_load_dt_keymap(dev, lradc);
+        if (error)
+                return error;
+
+        lradc->vref_supply = devm_regulator_get(dev, "vref");
+        if (IS_ERR(lradc->vref_supply))
+                return PTR_ERR(lradc->vref_supply);
+
+        lradc->dev = dev;
+        lradc->input = devm_input_allocate_device(dev);
+        if (!lradc->input)
+                return -ENOMEM;
+
+        lradc->input->name = pdev->name;
+        lradc->input->phys = "sun4i_lradc/input0";
+        lradc->input->open = sun4i_lradc_open;
+        lradc->input->close = sun4i_lradc_close;
+        lradc->input->id.bustype = BUS_HOST;
+        lradc->input->id.vendor = 0x0001;
+        lradc->input->id.product = 0x0001;
+        lradc->input->id.version = 0x0100;
+
+        __set_bit(EV_KEY, lradc->input->evbit);
+        for (i = 0; i < lradc->chan0_map_count; i++)
+                __set_bit(lradc->chan0_map[i].keycode, lradc->input->keybit);
+
+        input_set_drvdata(lradc->input, lradc);
+
+        lradc->base = devm_ioremap_resource(dev,
+                              platform_get_resource(pdev, IORESOURCE_MEM, 0));
+        if (IS_ERR(lradc->base))
+                return PTR_ERR(lradc->base);
+
+        error = devm_request_irq(dev, platform_get_irq(pdev, 0),
+                                 sun4i_lradc_irq, 0,
+                                 "sun4i-a10-lradc-keys", lradc);
+        if (error)
+                return error;
+
+        error = input_register_device(lradc->input);
+        if (error)
+                return error;
+
+        platform_set_drvdata(pdev, lradc);
+        return 0;
+}
+
+static const struct of_device_id sun4i_lradc_of_match[] = {
+        { .compatible = "allwinner,sun4i-a10-lradc-keys", },
+        { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, sun4i_lradc_of_match);
+
+static struct platform_driver sun4i_lradc_driver = {
+        .driver = {
+                .name   = "sun4i-a10-lradc-keys",
+                .of_match_table = of_match_ptr(sun4i_lradc_of_match),
+        },
+        .probe  = sun4i_lradc_probe,
+};
+
+module_platform_driver(sun4i_lradc_driver);
+
+MODULE_DESCRIPTION("Allwinner sun4i low res adc attached tablet keys driver");
+MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
+MODULE_LICENSE("GPL");