[PATCH] sm501: When registering the GPIO, turn on the GPIO unit's power

Josh Triplett josh at joshtriplett.org
Wed Jul 6 13:41:40 EST 2011

When attempting to use GPIO via the sm501 unit on the TQM5200 board,
GPIO operations would only function if during the same boot u-boot's
"fkt led" command had initialized the sm501.  Comparing the sm501's
registers with and without running the "fkt led" command turned up one
significant difference: u-boot had enabled the GPIO power gate.
Changing the Linux sm501 driver to enable the GPIO power gate allows
GPIO to work without first initializing it with u-boot.

Signed-off-by: Josh Triplett <josh at joshtriplett.org>
 drivers/mfd/sm501.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/mfd/sm501.c b/drivers/mfd/sm501.c
index df3702c..d7a0ab9 100644
--- a/drivers/mfd/sm501.c
+++ b/drivers/mfd/sm501.c
@@ -1089,6 +1089,7 @@ static int __devinit sm501_register_gpio(struct sm501_devdata *sm)
 		goto err_low_chip;
+	sm501_unit_power(sm->dev, SM501_GATE_GPIO, 1);
 	gpio->registered = 1;
 	return 0;
@@ -1118,6 +1119,8 @@ static void sm501_gpio_remove(struct sm501_devdata *sm)
 	if (!sm->gpio.registered)
+	sm501_unit_power(sm->dev, SM501_GATE_GPIO, 0);
 	ret = gpiochip_remove(&gpio->low.gpio);
 	if (ret)
 		dev_err(sm->dev, "cannot remove low chip, cannot tidy up\n");

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