From mboxrd@z Thu Jan 1 00:00:00 1970 From: thomas.petazzoni@free-electrons.com (Thomas Petazzoni) Date: Wed, 5 Sep 2012 11:20:12 +0200 Subject: [PATCH 5/8] gpio: 74x164: Add output pin support In-Reply-To: <1346834457-6257-5-git-send-email-maxime.ripard@free-electrons.com> References: <1346834457-6257-1-git-send-email-maxime.ripard@free-electrons.com> <1346834457-6257-5-git-send-email-maxime.ripard@free-electrons.com> Message-ID: <20120905112012.13ce2c86@skate> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Le Wed, 5 Sep 2012 10:40:54 +0200, Maxime Ripard a ?crit : > 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 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 -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com