From: thomas.petazzoni@free-electrons.com (Thomas Petazzoni)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 5/8] gpio: 74x164: Add output pin support
Date: Wed, 5 Sep 2012 14:29:52 +0200 [thread overview]
Message-ID: <20120905142952.2e1f12fd@skate> (raw)
In-Reply-To: <20120905142244.003e5e4b@eb-e6520>
Le Wed, 5 Sep 2012 14:22:44 +0200,
Eric B?nard <eric@eukrea.com> a ?crit :
> > > OK that's exactly what I was thinking to ;-)
> >
> > Good. So, do you think it's reasonable to use the STCP as a chip-select
> > for this device?
>
> in your case maybe but that really depends on how the chip is wired to
> the CPU so I'm not sure that can be a generic choice.
I'm not sure to see how this chip could be wired differently to the
CPU. The CPU must do a low-to-high transition on STCP to get the values
out from the internal register.
So, in other words, we don't know how to choose between:
*) Keep the current solution Maxime has implemented, where we have a
specific latch GPIO property in the Device Tree for this 74HC595,
and the 74HC595 driver is responsible for toggling this GPIO when
needed.
*) Use the internal SPI controller logic to control this pin as a
chip-select, and therefore get rid of Maxime's code with the
specific latch GPIO property in the Device Tree.
Thoughts?
Thomas
--
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
next prev parent reply other threads:[~2012-09-05 12:29 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-05 8:40 [PATCH 1/8] gpio: 74x164: Use module_spi_driver boiler plate function Maxime Ripard
2012-09-05 8:40 ` [PATCH 2/8] gpio: 74x164: Use devm_kzalloc Maxime Ripard
2012-09-05 8:46 ` Florian Fainelli
2012-09-05 9:16 ` Thomas Petazzoni
2012-09-06 7:22 ` Linus Walleij
2012-09-07 21:02 ` Linus Walleij
2012-09-05 8:40 ` [PATCH 3/8] gpio: 74x164: Remove platform data and use dynamic gpio number assignment Maxime Ripard
2012-09-05 8:48 ` Florian Fainelli
2012-09-05 9:15 ` Thomas Petazzoni
2012-09-05 9:17 ` Thomas Petazzoni
2012-09-05 8:40 ` [PATCH 4/8] gpio: 74x164: Add device tree support Maxime Ripard
2012-09-05 8:50 ` Florian Fainelli
2012-09-05 9:17 ` Thomas Petazzoni
2012-09-06 7:22 ` Linus Walleij
2012-09-05 8:40 ` [PATCH 5/8] gpio: 74x164: Add output pin support Maxime Ripard
2012-09-05 9:20 ` Thomas Petazzoni
2012-09-05 9:46 ` Eric Bénard
2012-09-05 10:09 ` Thomas Petazzoni
2012-09-05 10:26 ` Eric Bénard
2012-09-05 11:56 ` Thomas Petazzoni
2012-09-05 12:22 ` Eric Bénard
2012-09-05 12:29 ` Thomas Petazzoni [this message]
2012-09-05 12:54 ` Eric Bénard
2012-09-05 13:02 ` Maxime Ripard
2012-09-05 13:27 ` Eric Bénard
2012-09-05 8:40 ` [PATCH 6/8] gpio: 74x164: Add support for daisy-chaining Maxime Ripard
2012-09-05 8:56 ` Thomas Petazzoni
2012-09-05 8:40 ` [PATCH 7/8] gpio: 74x164: dts: Add documentation for the dt binding Maxime Ripard
2012-09-05 8:40 ` [PATCH 8/8] ARM: dts: cfa10049: Add the 74HC595 gpio expanders Maxime Ripard
2012-09-05 8:46 ` [PATCH 1/8] gpio: 74x164: Use module_spi_driver boiler plate function Florian Fainelli
2012-09-05 9:16 ` Thomas Petazzoni
2012-09-06 7:21 ` Linus Walleij
2012-09-06 14:10 ` Maxime Ripard
2012-09-07 21:09 ` Linus Walleij
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