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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 <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2012-01-21 18:21:50 +00:00
parent 2e95e51e18
commit c23bb602af
1 changed files with 12 additions and 6 deletions
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18
drivers/mfd/ucb1x00-core.c
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@ -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;