MFD: ucb1x00-core: fix gpiolib direction_output handling (c23bb602) · Commits · 戴 / test

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>

drivers/mfd/ucb1x00-core.c

+12 −6

Original line number	Diff line number	Diff line
		@@ -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);
		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;

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