Commit 45c0ce84 authored Mar 29, 2016 by Paul Kocialkowski Committed by Thierry Reding Sep 05, 2016

pwm: twl: Reliably disable TWL6030 PWMs

The current TWL6030 code for the TWL PWM driver does not reliably disable the
PWM output, as tested with LEDs. The previous commit to that driver introduced
that regression.

However, it does make sense to disable the PWM clock after resetting the PWM,
but for some obscure reason, doing it all at once simply doesn't work.

The TWL6030 datasheet mentions that PWMs have to be disabled in two distinct
steps. However, clearing the clock enable bit in a second step (after issuing a
reset first) does not work.

The only approach that works is the one that was in place before the previous
commit to the driver. It consists in enabling the PWM clock after issuing a
reset. This is what TI kernel trees and production code seem to be using.

However, adding an extra step to disable the PWM clock seems to work reliably,
despite looking quite odd.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

parent 29b4817d

drivers/pwm/pwm-twl.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -269,6 +269,22 @@ static void twl6030_pwm_disable(struct pwm_chip chip, struct pwm_device pwm)
		goto out;
		}

		val \|= TWL6030_PWM_TOGGLE(pwm->hwpwm, TWL6030_PWMXEN);

		ret = twl_i2c_write_u8(TWL6030_MODULE_ID1, val, TWL6030_TOGGLE3_REG);
		if (ret < 0) {
		dev_err(chip->dev, "%s: Failed to disable PWM\n", pwm->label);
		goto out;
		}

		val &= ~TWL6030_PWM_TOGGLE(pwm->hwpwm, TWL6030_PWMXEN);

		ret = twl_i2c_write_u8(TWL6030_MODULE_ID1, val, TWL6030_TOGGLE3_REG);
		if (ret < 0) {
		dev_err(chip->dev, "%s: Failed to disable PWM\n", pwm->label);
		goto out;
		}

		twl->twl6030_toggle3 = val;
		out:
		mutex_unlock(&twl->mutex);

Admin message