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authorDavid Brownell <dbrownell@users.sourceforge.net>2009-01-06 14:41:41 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-06 15:59:19 -0800
commitd29389de0b0ee1715333bafc6ac3f22a75aa4313 (patch)
tree6c4321359bd10231532d6cb2141f06070d8ddfd6 /drivers/spi/Kconfig
parentc2bacfc44f4b8d03dbaad5d2dca2fb4161e81975 (diff)
spi_gpio driver
Generalize the old at91rm9200 "bootstrap" bitbanging SPI master driver as "spi_gpio", so it works with arbitrary GPIOs and can be configured through platform_data. Such SPI masters support: - any number of bus instances (bus_num is the platform_device.id) - any number of chipselects (one GPIO per spi_device) - all four SPI_MODE values, and SPI_CS_HIGH - i/o word sizes from 1 to 32 bits; - devices configured as with any other spi_master controller When configured using platform_data, this provides relatively low clock rates. On platforms that support inlined GPIO calls, significantly improved transfer speeds are also possible with a semi-custom driver. (It's still painful when accessing flash memory, but less so.) Sanity checked by using this version to replace both native controllers on a board with six different SPI slaves, relying on three different SPI_MODE_* values and both SPI_CS_HIGH settings for correct operation. [akpm@linux-foundation.org: cleanups] Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Magnus Damm <damm@igel.co.jp> Tested-by: Magnus Damm <damm@igel.co.jp> Cc: Torgil Svensson <torgil.svensson@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/spi/Kconfig')
-rw-r--r--drivers/spi/Kconfig18
1 files changed, 17 insertions, 1 deletions
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index b9d0efb6803..4a6fe01831a 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -78,7 +78,7 @@ config SPI_AU1550
will be called au1550_spi.
config SPI_BITBANG
- tristate "Bitbanging SPI master"
+ tristate "Utilities for Bitbanging SPI masters"
help
With a few GPIO pins, your system can bitbang the SPI protocol.
Select this to get SPI support through I/O pins (GPIO, parallel
@@ -100,6 +100,22 @@ config SPI_BUTTERFLY
inexpensive battery powered microcontroller evaluation board.
This same cable can be used to flash new firmware.
+config SPI_GPIO
+ tristate "GPIO-based bitbanging SPI Master"
+ depends on GENERIC_GPIO
+ select SPI_BITBANG
+ help
+ This simple GPIO bitbanging SPI master uses the arch-neutral GPIO
+ interface to manage MOSI, MISO, SCK, and chipselect signals. SPI
+ slaves connected to a bus using this driver are configured as usual,
+ except that the spi_board_info.controller_data holds the GPIO number
+ for the chipselect used by this controller driver.
+
+ Note that this driver often won't achieve even 1 Mbit/sec speeds,
+ making it unusually slow for SPI. If your platform can inline
+ GPIO operations, you should be able to leverage that for better
+ speed with a custom version of this driver; see the source code.
+
config SPI_IMX
tristate "Freescale iMX SPI controller"
depends on ARCH_IMX && EXPERIMENTAL