1 // SPDX-License-Identifier: GPL-2.0-or-later
4  * e-book readers designed by the original design manufacturer Netronix, Inc.
13  * - The get_state callback is not implemented, because the current state of
15  * - The hardware can only generate normal polarity output.
16  * - The period and duty cycle can't be changed together in one atomic action.
45  * The time base used in the EC is 8MHz, or 125ns. Period and duty cycle are
58 						   int period, int duty)  in ntxec_pwm_set_raw_period_and_duty_cycle()  argument
63 	 * Changes to the period and duty cycle take effect as soon as the  in ntxec_pwm_set_raw_period_and_duty_cycle()
66 	 * duty cycle is fully written. If, in such a case, the old duty cycle  in ntxec_pwm_set_raw_period_and_duty_cycle()
69 	 * To minimize the time between the changes to period and duty cycle  in ntxec_pwm_set_raw_period_and_duty_cycle()
75 		{ NTXEC_REG_DUTY_HIGH, ntxec_reg8(duty >> 8) },  in ntxec_pwm_set_raw_period_and_duty_cycle()
77 		{ NTXEC_REG_DUTY_LOW, ntxec_reg8(duty) },  in ntxec_pwm_set_raw_period_and_duty_cycle()
80 	return regmap_multi_reg_write(priv->ec->regmap, regs, ARRAY_SIZE(regs));  in ntxec_pwm_set_raw_period_and_duty_cycle()
87 	unsigned int period, duty;  in ntxec_pwm_apply()  local
90 	if (state->polarity != PWM_POLARITY_NORMAL)  in ntxec_pwm_apply()
91 		return -EINVAL;  in ntxec_pwm_apply()
93 	period = min_t(u64, state->period, MAX_PERIOD_NS);  in ntxec_pwm_apply()
94 	duty   = min_t(u64, state->duty_cycle, period);  in ntxec_pwm_apply()
97 	duty   /= TIME_BASE_NS;  in ntxec_pwm_apply()
100 	 * Writing a duty cycle of zero puts the device into a state where  in ntxec_pwm_apply()
101 	 * writing a higher duty cycle doesn't result in the brightness that it  in ntxec_pwm_apply()
104 	 * As a workaround, write ENABLE=0 when the duty cycle is zero.  in ntxec_pwm_apply()
105 	 * The case that something has previously set the duty cycle to zero  in ntxec_pwm_apply()
108 	if (state->enabled && duty != 0) {  in ntxec_pwm_apply()
109 		res = ntxec_pwm_set_raw_period_and_duty_cycle(chip, period, duty);  in ntxec_pwm_apply()
113 		res = regmap_write(priv->ec->regmap, NTXEC_REG_ENABLE, ntxec_reg8(1));  in ntxec_pwm_apply()
117 		/* Disable the auto-off timer */  in ntxec_pwm_apply()
118 		res = regmap_write(priv->ec->regmap, NTXEC_REG_AUTO_OFF_HI, ntxec_reg8(0xff));  in ntxec_pwm_apply()
122 		return regmap_write(priv->ec->regmap, NTXEC_REG_AUTO_OFF_LO, ntxec_reg8(0xff));  in ntxec_pwm_apply()
124 		return regmap_write(priv->ec->regmap, NTXEC_REG_ENABLE, ntxec_reg8(0));  in ntxec_pwm_apply()
139 	struct ntxec *ec = dev_get_drvdata(pdev->dev.parent);  in ntxec_pwm_probe()
143 	device_set_of_node_from_dev(&pdev->dev, pdev->dev.parent);  in ntxec_pwm_probe()
145 	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);  in ntxec_pwm_probe()
147 		return -ENOMEM;  in ntxec_pwm_probe()
149 	priv->ec = ec;  in ntxec_pwm_probe()
151 	chip = &priv->chip;  in ntxec_pwm_probe()
152 	chip->dev = &pdev->dev;  in ntxec_pwm_probe()
153 	chip->ops = &ntxec_pwm_ops;  in ntxec_pwm_probe()
154 	chip->npwm = 1;  in ntxec_pwm_probe()
156 	return devm_pwmchip_add(&pdev->dev, chip);  in ntxec_pwm_probe()
161 		.name = "ntxec-pwm",
170 MODULE_ALIAS("platform:ntxec-pwm");