From c23bb602af24a635d0894aa7091e184385bf8a9f Mon Sep 17 00:00:00 2001 From: Russell King Date: Sat, 21 Jan 2012 18:21:50 +0000 Subject: [PATCH] MFD: ucb1x00-core: fix gpiolib direction_output handling gpiolib drivers should first set the output data before setting the direction to avoid putting glitches on an output signal. As an additional bonus, we tweak the code to avoid unnecessary register writes to the output and direction registers if they have no need to be updated. Signed-off-by: Russell King --- drivers/mfd/ucb1x00-core.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/drivers/mfd/ucb1x00-core.c b/drivers/mfd/ucb1x00-core.c index 8ebda97981e1..febc90cdef7e 100644 --- a/drivers/mfd/ucb1x00-core.c +++ b/drivers/mfd/ucb1x00-core.c @@ -148,16 +148,22 @@ static int ucb1x00_gpio_direction_output(struct gpio_chip *chip, unsigned offset { struct ucb1x00 *ucb = container_of(chip, struct ucb1x00, gpio); unsigned long flags; + unsigned old, mask = 1 << offset; spin_lock_irqsave(&ucb->io_lock, flags); - ucb->io_dir |= (1 << offset); - ucb1x00_reg_write(ucb, UCB_IO_DIR, ucb->io_dir); - + old = ucb->io_out; if (value) - ucb->io_out |= 1 << offset; + ucb->io_out |= mask; else - ucb->io_out &= ~(1 << offset); - ucb1x00_reg_write(ucb, UCB_IO_DATA, ucb->io_out); + ucb->io_out &= ~mask; + + if (old != ucb->io_out) + ucb1x00_reg_write(ucb, UCB_IO_DATA, ucb->io_out); + + if (!(ucb->io_dir & mask)) { + ucb->io_dir |= mask; + ucb1x00_reg_write(ucb, UCB_IO_DIR, ucb->io_dir); + } spin_unlock_irqrestore(&ucb->io_lock, flags); return 0; -- 2.30.2