drivers/video/backlight/pandora_bl.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Backlight driver for Pandora handheld.
 * Pandora uses TWL4030 PWM0 -> TPS61161 combo for control backlight.
 * Based on pwm_bl.c
 *
 * Copyright 2009,2012 Gražvydas Ignotas <notasas@gmail.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/backlight.h>
#include <linux/mfd/twl.h>
#include <linux/err.h>

#define TWL_PWM0_ON		0x00
#define TWL_PWM0_OFF		0x01

#define TWL_INTBR_GPBR1		0x0c
#define TWL_INTBR_PMBR1		0x0d

#define TWL_PMBR1_PWM0_MUXMASK	0x0c
#define TWL_PMBR1_PWM0		0x04
#define PWM0_CLK_ENABLE		BIT(0)
#define PWM0_ENABLE		BIT(2)

/* range accepted by hardware */
#define MIN_VALUE 9
#define MAX_VALUE 63
#define MAX_USER_VALUE (MAX_VALUE - MIN_VALUE)

struct pandora_private {
	unsigned old_state;
#define PANDORABL_WAS_OFF 1
};

static int pandora_backlight_update_status(struct backlight_device *bl)
{
	int brightness = bl->props.brightness;
	struct pandora_private *priv = bl_get_data(bl);
	u8 r;

	if (bl->props.power != BACKLIGHT_POWER_ON)
		brightness = 0;
	if (bl->props.state & BL_CORE_FBBLANK)
		brightness = 0;
	if (bl->props.state & BL_CORE_SUSPENDED)
		brightness = 0;

	if ((unsigned int)brightness > MAX_USER_VALUE)
		brightness = MAX_USER_VALUE;

	if (brightness == 0) {
		if (priv->old_state == PANDORABL_WAS_OFF)
			goto done;

		/* first disable PWM0 output, then clock */
		twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
		r &= ~PWM0_ENABLE;
		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
		r &= ~PWM0_CLK_ENABLE;
		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);

		goto done;
	}

	if (priv->old_state == PANDORABL_WAS_OFF) {
		/*
		 * set PWM duty cycle to max. TPS61161 seems to use this
		 * to calibrate it's PWM sensitivity when it starts.
		 */
		twl_i2c_write_u8(TWL_MODULE_PWM, MAX_VALUE, TWL_PWM0_OFF);

		/* first enable clock, then PWM0 out */
		twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
		r &= ~PWM0_ENABLE;
		r |= PWM0_CLK_ENABLE;
		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
		r |= PWM0_ENABLE;
		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);

		/*
		 * TI made it very easy to enable digital control, so easy that
		 * it often triggers unintentionally and disabes PWM control,
		 * so wait until 1 wire mode detection window ends.
		 */
		usleep_range(2000, 10000);
	}

	twl_i2c_write_u8(TWL_MODULE_PWM, MIN_VALUE + brightness, TWL_PWM0_OFF);

done:
	if (brightness != 0)
		priv->old_state = 0;
	else
		priv->old_state = PANDORABL_WAS_OFF;

	return 0;
}

static const struct backlight_ops pandora_backlight_ops = {
	.options	= BL_CORE_SUSPENDRESUME,
	.update_status	= pandora_backlight_update_status,
};

static int pandora_backlight_probe(struct platform_device *pdev)
{
	struct backlight_properties props;
	struct backlight_device *bl;
	struct pandora_private *priv;
	u8 r;

	priv = devm_kmalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	memset(&props, 0, sizeof(props));
	props.max_brightness = MAX_USER_VALUE;
	props.type = BACKLIGHT_RAW;
	bl = devm_backlight_device_register(&pdev->dev, pdev->name, &pdev->dev,
					priv, &pandora_backlight_ops, &props);
	if (IS_ERR(bl)) {
		dev_err(&pdev->dev, "failed to register backlight\n");
		return PTR_ERR(bl);
	}

	platform_set_drvdata(pdev, bl);

	/* 64 cycle period, ON position 0 */
	twl_i2c_write_u8(TWL_MODULE_PWM, 0x80, TWL_PWM0_ON);

	priv->old_state = PANDORABL_WAS_OFF;
	bl->props.brightness = MAX_USER_VALUE;
	backlight_update_status(bl);

	/* enable PWM function in pin mux */
	twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_PMBR1);
	r &= ~TWL_PMBR1_PWM0_MUXMASK;
	r |= TWL_PMBR1_PWM0;
	twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_PMBR1);

	return 0;
}

static struct platform_driver pandora_backlight_driver = {
	.driver		= {
		.name	= "pandora-backlight",
	},
	.probe		= pandora_backlight_probe,
};

module_platform_driver(pandora_backlight_driver);

MODULE_AUTHOR("Gražvydas Ignotas <notasas@gmail.com>");
MODULE_DESCRIPTION("Pandora Backlight Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pandora-backlight");