ep93xx_bl.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Driver for the Cirrus EP93xx lcd backlight
  4 *
  5 * Copyright (c) 2010 H Hartley Sweeten <hsweeten@visionengravers.com>
  6 *
  7 * This driver controls the pulse width modulated brightness control output,
  8 * BRIGHT, on the Cirrus EP9307, EP9312, and EP9315 processors.
  9 */
 10
 11#include <linux/module.h>
 12#include <linux/platform_device.h>
 13#include <linux/io.h>
 14#include <linux/backlight.h>
 15
 16#define EP93XX_MAX_COUNT		255
 17#define EP93XX_MAX_BRIGHT		255
 18#define EP93XX_DEF_BRIGHT		128
 19
 20struct ep93xxbl {
 21	void __iomem *mmio;
 22	int brightness;
 23};
 24
 25static int ep93xxbl_set(struct backlight_device *bl, int brightness)
 26{
 27	struct ep93xxbl *ep93xxbl = bl_get_data(bl);
 28
 29	writel((brightness << 8) | EP93XX_MAX_COUNT, ep93xxbl->mmio);
 30
 31	ep93xxbl->brightness = brightness;
 32
 33	return 0;
 34}
 35
 36static int ep93xxbl_update_status(struct backlight_device *bl)
 37{
 38	return ep93xxbl_set(bl, backlight_get_brightness(bl));
 39}
 40
 41static int ep93xxbl_get_brightness(struct backlight_device *bl)
 42{
 43	struct ep93xxbl *ep93xxbl = bl_get_data(bl);
 44
 45	return ep93xxbl->brightness;
 46}
 47
 48static const struct backlight_ops ep93xxbl_ops = {
 49	.update_status	= ep93xxbl_update_status,
 50	.get_brightness	= ep93xxbl_get_brightness,
 51};
 52
 53static int ep93xxbl_probe(struct platform_device *dev)
 54{
 55	struct ep93xxbl *ep93xxbl;
 56	struct backlight_device *bl;
 57	struct backlight_properties props;
 58	struct resource *res;
 59
 60	ep93xxbl = devm_kzalloc(&dev->dev, sizeof(*ep93xxbl), GFP_KERNEL);
 61	if (!ep93xxbl)
 62		return -ENOMEM;
 63
 64	res = platform_get_resource(dev, IORESOURCE_MEM, 0);
 65	if (!res)
 66		return -ENXIO;
 67
 68	/*
 69	 * FIXME - We don't do a request_mem_region here because we are
 70	 * sharing the register space with the framebuffer driver (see
 71	 * drivers/video/ep93xx-fb.c) and doing so will cause the second
 72	 * loaded driver to return -EBUSY.
 73	 *
 74	 * NOTE: No locking is required; the framebuffer does not touch
 75	 * this register.
 76	 */
 77	ep93xxbl->mmio = devm_ioremap(&dev->dev, res->start,
 78				      resource_size(res));
 79	if (!ep93xxbl->mmio)
 80		return -ENXIO;
 81
 82	memset(&props, 0, sizeof(struct backlight_properties));
 83	props.type = BACKLIGHT_RAW;
 84	props.max_brightness = EP93XX_MAX_BRIGHT;
 85	bl = devm_backlight_device_register(&dev->dev, dev->name, &dev->dev,
 86					ep93xxbl, &ep93xxbl_ops, &props);
 87	if (IS_ERR(bl))
 88		return PTR_ERR(bl);
 89
 90	bl->props.brightness = EP93XX_DEF_BRIGHT;
 91
 92	platform_set_drvdata(dev, bl);
 93
 94	ep93xxbl_update_status(bl);
 95
 96	return 0;
 97}
 98
 99#ifdef CONFIG_PM_SLEEP
100static int ep93xxbl_suspend(struct device *dev)
101{
102	struct backlight_device *bl = dev_get_drvdata(dev);
103
104	return ep93xxbl_set(bl, 0);
105}
106
107static int ep93xxbl_resume(struct device *dev)
108{
109	struct backlight_device *bl = dev_get_drvdata(dev);
110
111	backlight_update_status(bl);
112	return 0;
113}
114#endif
115
116static SIMPLE_DEV_PM_OPS(ep93xxbl_pm_ops, ep93xxbl_suspend, ep93xxbl_resume);
117
118static struct platform_driver ep93xxbl_driver = {
119	.driver		= {
120		.name	= "ep93xx-bl",
121		.pm	= &ep93xxbl_pm_ops,
122	},
123	.probe		= ep93xxbl_probe,
124};
125
126module_platform_driver(ep93xxbl_driver);
127
128MODULE_DESCRIPTION("EP93xx Backlight Driver");
129MODULE_AUTHOR("H Hartley Sweeten <hsweeten@visionengravers.com>");
130MODULE_LICENSE("GPL");
131MODULE_ALIAS("platform:ep93xx-bl");