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| author | David Brownell <dbrownell@users.sourceforge.net> | 2009-01-06 14:41:41 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-06 15:59:19 -0800 |
| commit | d29389de0b0ee1715333bafc6ac3f22a75aa4313 (patch) | |
| tree | 6c4321359bd10231532d6cb2141f06070d8ddfd6 /drivers/spi/Kconfig | |
| parent | c2bacfc44f4b8d03dbaad5d2dca2fb4161e81975 (diff) | |
| download | lwn-d29389de0b0ee1715333bafc6ac3f22a75aa4313.tar.gz lwn-d29389de0b0ee1715333bafc6ac3f22a75aa4313.zip | |
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/Kconfig | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig index b9d0efb6803f..4a6fe01831a8 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 |