backlight: Add WM831x backlight driver

The WM831x series of PMICs provide DC-DC boost convertors and current
sinks which can be used together to drive LEDs for use as backlights.
Expose this functionality via the backlight API.

Since when used in this configuration the current sink and boost
convertor are very tightly coupled with a multi-stage startup for
the current sink which overlaps with the boost convertor startup
this driver bypasses the regulator API. Machine inititialisation
is responsible for ensuring that the regulators are not accessed
via both APIs.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

drivers/video/backlight/Kconfig

@@ -229,3 +229,10 @@ config BACKLIGHT_SAHARA
 	help
 	  If you have a Tabletkiosk Sahara Touch-iT, say y to enable the
 	  backlight driver.
+
+config BACKLIGHT_WM831X
+	tristate "WM831x PMIC Backlight Driver"
+	depends on BACKLIGHT_CLASS_DEVICE && MFD_WM831X
+	help
+	  If you have a backlight driven by the ISINK and DCDC of a
+	  WM831x PMIC say y to enable the backlight driver for it.

drivers/video/backlight/Makefile

@@ -24,4 +24,5 @@ obj-$(CONFIG_BACKLIGHT_DA903X)	+= da903x_bl.o
 obj-$(CONFIG_BACKLIGHT_MBP_NVIDIA) += mbp_nvidia_bl.o
 obj-$(CONFIG_BACKLIGHT_TOSA)	+= tosa_bl.o
 obj-$(CONFIG_BACKLIGHT_SAHARA)	+= kb3886_bl.o
+obj-$(CONFIG_BACKLIGHT_WM831X)	+= wm831x_bl.o
 

drivers/video/backlight/wm831x_bl.c

@@ -0,0 +1,250 @@
+/*
+ * Backlight driver for Wolfson Microelectronics WM831x PMICs
+ *
+ * Copyright 2009 Wolfson Microelectonics plc
+ *
+ * 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/init.h>
+#include <linux/platform_device.h>
+#include <linux/fb.h>
+#include <linux/backlight.h>
+
+#include <linux/mfd/wm831x/core.h>
+#include <linux/mfd/wm831x/pdata.h>
+#include <linux/mfd/wm831x/regulator.h>
+
+struct wm831x_backlight_data {
+	struct wm831x *wm831x;
+	int isink_reg;
+	int current_brightness;
+};
+
+static int wm831x_backlight_set(struct backlight_device *bl, int brightness)
+{
+	struct wm831x_backlight_data *data = bl_get_data(bl);
+	struct wm831x *wm831x = data->wm831x;
+	int power_up = !data->current_brightness && brightness;
+	int power_down = data->current_brightness && !brightness;
+	int ret;
+
+	if (power_up) {
+		/* Enable the ISINK */
+		ret = wm831x_set_bits(wm831x, data->isink_reg,
+				      WM831X_CS1_ENA, WM831X_CS1_ENA);
+		if (ret < 0)
+			goto err;
+
+		/* Enable the DC-DC */
+		ret = wm831x_set_bits(wm831x, WM831X_DCDC_ENABLE,
+				      WM831X_DC4_ENA, WM831X_DC4_ENA);
+		if (ret < 0)
+			goto err;
+	}
+
+	if (power_down) {
+		/* DCDC first */
+		ret = wm831x_set_bits(wm831x, WM831X_DCDC_ENABLE,
+				      WM831X_DC4_ENA, 0);
+		if (ret < 0)
+			goto err;
+
+		/* ISINK */
+		ret = wm831x_set_bits(wm831x, data->isink_reg,
+				      WM831X_CS1_DRIVE | WM831X_CS1_ENA, 0);
+		if (ret < 0)
+			goto err;
+	}
+
+	/* Set the new brightness */
+	ret = wm831x_set_bits(wm831x, data->isink_reg,
+			      WM831X_CS1_ISEL_MASK, brightness);
+	if (ret < 0)
+		goto err;
+
+	if (power_up) {
+		/* Drive current through the ISINK */
+		ret = wm831x_set_bits(wm831x, data->isink_reg,
+				      WM831X_CS1_DRIVE, WM831X_CS1_DRIVE);
+		if (ret < 0)
+			return ret;
+	}
+
+	data->current_brightness = brightness;
+
+	return 0;
+
+err:
+	/* If we were in the middle of a power transition always shut down
+	 * for safety.
+	 */
+	if (power_up || power_down) {
+		wm831x_set_bits(wm831x, WM831X_DCDC_ENABLE, WM831X_DC4_ENA, 0);
+		wm831x_set_bits(wm831x, data->isink_reg, WM831X_CS1_ENA, 0);
+	}
+
+	return ret;
+}
+
+static int wm831x_backlight_update_status(struct backlight_device *bl)
+{
+	int brightness = bl->props.brightness;
+
+	if (bl->props.power != FB_BLANK_UNBLANK)
+		brightness = 0;
+
+	if (bl->props.fb_blank != FB_BLANK_UNBLANK)
+		brightness = 0;
+
+	if (bl->props.state & BL_CORE_SUSPENDED)
+		brightness = 0;
+
+	return wm831x_backlight_set(bl, brightness);
+}
+
+static int wm831x_backlight_get_brightness(struct backlight_device *bl)
+{
+	struct wm831x_backlight_data *data = bl_get_data(bl);
+	return data->current_brightness;
+}
+
+static struct backlight_ops wm831x_backlight_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.update_status	= wm831x_backlight_update_status,
+	.get_brightness	= wm831x_backlight_get_brightness,
+};
+
+static int wm831x_backlight_probe(struct platform_device *pdev)
+{
+	struct wm831x *wm831x = dev_get_drvdata(pdev->dev.parent);
+	struct wm831x_pdata *wm831x_pdata;
+	struct wm831x_backlight_pdata *pdata;
+	struct wm831x_backlight_data *data;
+	struct backlight_device *bl;
+	int ret, i, max_isel, isink_reg, dcdc_cfg;
+
+	/* We need platform data */
+	if (pdev->dev.parent->platform_data) {
+		wm831x_pdata = pdev->dev.parent->platform_data;
+		pdata = wm831x_pdata->backlight;
+	} else {
+		pdata = NULL;
+	}
+
+	if (!pdata) {
+		dev_err(&pdev->dev, "No platform data supplied\n");
+		return -EINVAL;
+	}
+
+	/* Figure out the maximum current we can use */
+	for (i = 0; i < WM831X_ISINK_MAX_ISEL; i++) {
+		if (wm831x_isinkv_values[i] > pdata->max_uA)
+			break;
+	}
+
+	if (i == 0) {
+		dev_err(&pdev->dev, "Invalid max_uA: %duA\n", pdata->max_uA);
+		return -EINVAL;
+	}
+	max_isel = i - 1;
+
+	if (pdata->max_uA != wm831x_isinkv_values[max_isel])
+		dev_warn(&pdev->dev,
+			 "Maximum current is %duA not %duA as requested\n",
+			 wm831x_isinkv_values[max_isel], pdata->max_uA);
+
+	switch (pdata->isink) {
+	case 1:
+		isink_reg = WM831X_CURRENT_SINK_1;
+		dcdc_cfg = 0;
+		break;
+	case 2:
+		isink_reg = WM831X_CURRENT_SINK_2;
+		dcdc_cfg = WM831X_DC4_FBSRC;
+		break;
+	default:
+		dev_err(&pdev->dev, "Invalid ISINK %d\n", pdata->isink);
+		return -EINVAL;
+	}
+
+	/* Configure the ISINK to use for feedback */
+	ret = wm831x_reg_unlock(wm831x);
+	if (ret < 0)
+		return ret;
+
+	ret = wm831x_set_bits(wm831x, WM831X_DC4_CONTROL, WM831X_DC4_FBSRC,
+			      dcdc_cfg);
+
+	wm831x_reg_lock(wm831x);
+	if (ret < 0)
+		return ret;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (data == NULL)
+		return -ENOMEM;
+
+	data->wm831x = wm831x;
+	data->current_brightness = 0;
+	data->isink_reg = isink_reg;
+
+	bl = backlight_device_register("wm831x", &pdev->dev,
+			data, &wm831x_backlight_ops);
+	if (IS_ERR(bl)) {
+		dev_err(&pdev->dev, "failed to register backlight\n");
+		kfree(data);
+		return PTR_ERR(bl);
+	}
+
+	bl->props.max_brightness = max_isel;
+	bl->props.brightness = max_isel;
+
+	platform_set_drvdata(pdev, bl);
+
+	/* Disable the DCDC if it was started so we can bootstrap */
+	wm831x_set_bits(wm831x, WM831X_DCDC_ENABLE, WM831X_DC4_ENA, 0);
+
+
+	backlight_update_status(bl);
+
+	return 0;
+}
+
+static int wm831x_backlight_remove(struct platform_device *pdev)
+{
+	struct backlight_device *bl = platform_get_drvdata(pdev);
+	struct wm831x_backlight_data *data = bl_get_data(bl);
+
+	backlight_device_unregister(bl);
+	kfree(data);
+	return 0;
+}
+
+static struct platform_driver wm831x_backlight_driver = {
+	.driver		= {
+		.name	= "wm831x-backlight",
+		.owner	= THIS_MODULE,
+	},
+	.probe		= wm831x_backlight_probe,
+	.remove		= wm831x_backlight_remove,
+};
+
+static int __init wm831x_backlight_init(void)
+{
+	return platform_driver_register(&wm831x_backlight_driver);
+}
+module_init(wm831x_backlight_init);
+
+static void __exit wm831x_backlight_exit(void)
+{
+	platform_driver_unregister(&wm831x_backlight_driver);
+}
+module_exit(wm831x_backlight_exit);
+
+MODULE_DESCRIPTION("Backlight Driver for WM831x PMICs");
+MODULE_AUTHOR("Mark Brown <broonie@opensource.wolfsonmicro.com");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:wm831x-backlight");