[PATCH 5/8] gpio: 74x164: Add output pin support

Thomas Petazzoni thomas.petazzoni at free-electrons.com
Wed Sep 5 05:20:12 EDT 2012

Le Wed,  5 Sep 2012 10:40:54 +0200,
Maxime Ripard <maxime.ripard at free-electrons.com> a écrit :

> The shift registers have an output that, when enabled, propagates the
> values of its internal register to the pins. Make use of this pin
> through the output-latch-gpio dt property.
> Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>

Well, thinking more about this, and reviewing the i.MX 28 datasheet a
bit more thoroughly, I don't think you need this GPIO thing. It is an
active-low pin that should be kept low during the entire duration of
the transfer, which basically is a chip select. And in turns out that
the CFA10049 board uses pins that can be controlled as chip selects
directly by the SPI controller, so you should rather use this rather
than introduce a specially handled GPIO. This needs testing, but I
don't see why it wouldn't work.

Best regards,

Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.

More information about the linux-arm-kernel mailing list