Re: [PATCH 2/2 v2] SPI: spi-pxa2xx: SPI support for Intel Quark X1000
From: Bryan O'Donoghue
Date: Wed Oct 08 2014 - 05:02:23 EST
On 08/10/14 08:48, Chen, Alvin wrote:
Now, we have another board which can support 4 slave spi per master, but not only Galileo. Since that board is not public, after discussing with team, we decide to make the
upstream code to support '1'.
I will change it back to
.num_chipselect = 1,
The important thing in terms of Galileo is to ensure that a GPIO can be
used for chip-select.
The user-space API ported from Arduino to Linux wants to control it's
own chip-select directly - so the internal chip-select of the Quark SPI
master can - and does de-assert while doing SPI transactions on Galileo.
The CS on the master is tied to FIFO occupancy - so at higher bit-rates
we can fail to keep the FIFO occupied :(
That doesn't matter though, because the pinned out SPI:CS on the Arduino
header is a GPIO.
From the perspective of the Arduino code in user-space and the slave
hardware @ the other end of the SPI bus - we see a nice and consistent
chip-select for the entire duration of the SPI transaction - even though
the actual SPI:CS coming from the SoC can *waggle* - when FIFOs go empty.
IMO - so long as you've tested on Galileo and seen working SPI - you're
good to go anyway.
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