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>
This commit is contained in:
David Brownell
Linus Torvalds
Родитель
c2bacfc44f
Коммит
d29389de0b
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@ -78,7 +78,7 @@ config SPI_AU1550
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will be called au1550_spi.
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config SPI_BITBANG
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tristate "Bitbanging SPI master"
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tristate "Utilities for Bitbanging SPI masters"
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help
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With a few GPIO pins, your system can bitbang the SPI protocol.
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Select this to get SPI support through I/O pins (GPIO, parallel
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@ -100,6 +100,22 @@ config SPI_BUTTERFLY
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inexpensive battery powered microcontroller evaluation board.
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This same cable can be used to flash new firmware.
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config SPI_GPIO
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tristate "GPIO-based bitbanging SPI Master"
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depends on GENERIC_GPIO
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select SPI_BITBANG
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help
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This simple GPIO bitbanging SPI master uses the arch-neutral GPIO
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interface to manage MOSI, MISO, SCK, and chipselect signals. SPI
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slaves connected to a bus using this driver are configured as usual,
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except that the spi_board_info.controller_data holds the GPIO number
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for the chipselect used by this controller driver.
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Note that this driver often won't achieve even 1 Mbit/sec speeds,
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making it unusually slow for SPI. If your platform can inline
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GPIO operations, you should be able to leverage that for better
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speed with a custom version of this driver; see the source code.
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config SPI_IMX
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tristate "Freescale iMX SPI controller"
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depends on ARCH_IMX && EXPERIMENTAL
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@ -16,6 +16,7 @@ obj-$(CONFIG_SPI_BFIN) += spi_bfin5xx.o
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obj-$(CONFIG_SPI_BITBANG) += spi_bitbang.o
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obj-$(CONFIG_SPI_AU1550) += au1550_spi.o
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obj-$(CONFIG_SPI_BUTTERFLY) += spi_butterfly.o
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obj-$(CONFIG_SPI_GPIO) += spi_gpio.o
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obj-$(CONFIG_SPI_IMX) += spi_imx.o
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obj-$(CONFIG_SPI_LM70_LLP) += spi_lm70llp.o
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obj-$(CONFIG_SPI_PXA2XX) += pxa2xx_spi.o
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@ -0,0 +1,360 @@
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/*
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* spi_gpio.c - SPI master driver using generic bitbanged GPIO
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*
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* Copyright (C) 2006,2008 David Brownell
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/platform_device.h>
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#include <linux/gpio.h>
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#include <linux/spi/spi.h>
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#include <linux/spi/spi_bitbang.h>
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#include <linux/spi/spi_gpio.h>
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/*
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* This bitbanging SPI master driver should help make systems usable
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* when a native hardware SPI engine is not available, perhaps because
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* its driver isn't yet working or because the I/O pins it requires
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* are used for other purposes.
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*
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* platform_device->driver_data ... points to spi_gpio
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*
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* spi->controller_state ... reserved for bitbang framework code
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* spi->controller_data ... holds chipselect GPIO
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*
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* spi->master->dev.driver_data ... points to spi_gpio->bitbang
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*/
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struct spi_gpio {
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struct spi_bitbang bitbang;
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struct spi_gpio_platform_data pdata;
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struct platform_device *pdev;
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};
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/*----------------------------------------------------------------------*/
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/*
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* Because the overhead of going through four GPIO procedure calls
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* per transferred bit can make performance a problem, this code
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* is set up so that you can use it in either of two ways:
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*
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* - The slow generic way: set up platform_data to hold the GPIO
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* numbers used for MISO/MOSI/SCK, and issue procedure calls for
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* each of them. This driver can handle several such busses.
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*
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* - The quicker inlined way: only helps with platform GPIO code
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* that inlines operations for constant GPIOs. This can give
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* you tight (fast!) inner loops, but each such bus needs a
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* new driver. You'll define a new C file, with Makefile and
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* Kconfig support; the C code can be a total of six lines:
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*
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* #define DRIVER_NAME "myboard_spi2"
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* #define SPI_MISO_GPIO 119
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* #define SPI_MOSI_GPIO 120
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* #define SPI_SCK_GPIO 121
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* #define SPI_N_CHIPSEL 4
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* #include "spi_gpio.c"
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*/
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#ifndef DRIVER_NAME
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#define DRIVER_NAME "spi_gpio"
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#define GENERIC_BITBANG /* vs tight inlines */
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/* all functions referencing these symbols must define pdata */
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#define SPI_MISO_GPIO ((pdata)->miso)
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#define SPI_MOSI_GPIO ((pdata)->mosi)
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#define SPI_SCK_GPIO ((pdata)->sck)
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#define SPI_N_CHIPSEL ((pdata)->num_chipselect)
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#endif
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/*----------------------------------------------------------------------*/
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static inline const struct spi_gpio_platform_data * __pure
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spi_to_pdata(const struct spi_device *spi)
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{
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const struct spi_bitbang *bang;
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const struct spi_gpio *spi_gpio;
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bang = spi_master_get_devdata(spi->master);
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spi_gpio = container_of(bang, struct spi_gpio, bitbang);
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return &spi_gpio->pdata;
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}
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/* this is #defined to avoid unused-variable warnings when inlining */
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#define pdata spi_to_pdata(spi)
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static inline void setsck(const struct spi_device *spi, int is_on)
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{
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gpio_set_value(SPI_SCK_GPIO, is_on);
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}
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static inline void setmosi(const struct spi_device *spi, int is_on)
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{
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gpio_set_value(SPI_MOSI_GPIO, is_on);
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}
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static inline int getmiso(const struct spi_device *spi)
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{
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return gpio_get_value(SPI_MISO_GPIO);
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}
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#undef pdata
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/*
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* NOTE: this clocks "as fast as we can". It "should" be a function of the
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* requested device clock. Software overhead means we usually have trouble
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* reaching even one Mbit/sec (except when we can inline bitops), so for now
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* we'll just assume we never need additional per-bit slowdowns.
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*/
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#define spidelay(nsecs) do {} while (0)
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#define EXPAND_BITBANG_TXRX
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#include <linux/spi/spi_bitbang.h>
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/*
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* These functions can leverage inline expansion of GPIO calls to shrink
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* costs for a txrx bit, often by factors of around ten (by instruction
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* count). That is particularly visible for larger word sizes, but helps
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* even with default 8-bit words.
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*
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* REVISIT overheads calling these functions for each word also have
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* significant performance costs. Having txrx_bufs() calls that inline
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* the txrx_word() logic would help performance, e.g. on larger blocks
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* used with flash storage or MMC/SD. There should also be ways to make
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* GCC be less stupid about reloading registers inside the I/O loops,
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* even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3?
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*/
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static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi,
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unsigned nsecs, u32 word, u8 bits)
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{
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return bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);
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}
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static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
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unsigned nsecs, u32 word, u8 bits)
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{
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return bitbang_txrx_be_cpha1(spi, nsecs, 0, word, bits);
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}
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static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
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unsigned nsecs, u32 word, u8 bits)
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{
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return bitbang_txrx_be_cpha0(spi, nsecs, 1, word, bits);
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}
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static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
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unsigned nsecs, u32 word, u8 bits)
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{
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return bitbang_txrx_be_cpha1(spi, nsecs, 1, word, bits);
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}
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/*----------------------------------------------------------------------*/
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static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
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{
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unsigned long cs = (unsigned long) spi->controller_data;
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/* set initial clock polarity */
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if (is_active)
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setsck(spi, spi->mode & SPI_CPOL);
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/* SPI is normally active-low */
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gpio_set_value(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
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}
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static int spi_gpio_setup(struct spi_device *spi)
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{
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unsigned long cs = (unsigned long) spi->controller_data;
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int status = 0;
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if (spi->bits_per_word > 32)
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return -EINVAL;
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if (!spi->controller_state) {
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status = gpio_request(cs, spi->dev.bus_id);
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if (status)
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return status;
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status = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
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}
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if (!status)
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status = spi_bitbang_setup(spi);
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if (status) {
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if (!spi->controller_state)
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gpio_free(cs);
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}
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return status;
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}
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static void spi_gpio_cleanup(struct spi_device *spi)
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{
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unsigned long cs = (unsigned long) spi->controller_data;
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gpio_free(cs);
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spi_bitbang_cleanup(spi);
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}
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static int __init spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
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{
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int value;
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value = gpio_request(pin, label);
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if (value == 0) {
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if (is_in)
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value = gpio_direction_input(pin);
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else
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value = gpio_direction_output(pin, 0);
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}
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return value;
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}
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static int __init
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spi_gpio_request(struct spi_gpio_platform_data *pdata, const char *label)
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{
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int value;
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/* NOTE: SPI_*_GPIO symbols may reference "pdata" */
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value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false);
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if (value)
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goto done;
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value = spi_gpio_alloc(SPI_MISO_GPIO, label, true);
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if (value)
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goto free_mosi;
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value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
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if (value)
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goto free_miso;
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goto done;
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free_miso:
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gpio_free(SPI_MISO_GPIO);
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free_mosi:
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gpio_free(SPI_MOSI_GPIO);
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done:
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return value;
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}
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static int __init spi_gpio_probe(struct platform_device *pdev)
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{
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int status;
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struct spi_master *master;
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struct spi_gpio *spi_gpio;
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struct spi_gpio_platform_data *pdata;
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pdata = pdev->dev.platform_data;
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#ifdef GENERIC_BITBANG
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if (!pdata || !pdata->num_chipselect)
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return -ENODEV;
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#endif
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status = spi_gpio_request(pdata, dev_name(&pdev->dev));
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if (status < 0)
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return status;
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master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio);
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if (!master) {
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status = -ENOMEM;
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goto gpio_free;
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}
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spi_gpio = spi_master_get_devdata(master);
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platform_set_drvdata(pdev, spi_gpio);
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spi_gpio->pdev = pdev;
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if (pdata)
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spi_gpio->pdata = *pdata;
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master->bus_num = pdev->id;
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master->num_chipselect = SPI_N_CHIPSEL;
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master->setup = spi_gpio_setup;
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master->cleanup = spi_gpio_cleanup;
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spi_gpio->bitbang.master = spi_master_get(master);
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spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
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spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
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spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
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spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
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spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
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spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
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spi_gpio->bitbang.flags = SPI_CS_HIGH;
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status = spi_bitbang_start(&spi_gpio->bitbang);
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if (status < 0) {
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spi_master_put(spi_gpio->bitbang.master);
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gpio_free:
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gpio_free(SPI_MISO_GPIO);
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gpio_free(SPI_MOSI_GPIO);
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gpio_free(SPI_SCK_GPIO);
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spi_master_put(master);
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}
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return status;
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}
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static int __exit spi_gpio_remove(struct platform_device *pdev)
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{
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struct spi_gpio *spi_gpio;
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struct spi_gpio_platform_data *pdata;
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int status;
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spi_gpio = platform_get_drvdata(pdev);
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pdata = pdev->dev.platform_data;
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/* stop() unregisters child devices too */
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status = spi_bitbang_stop(&spi_gpio->bitbang);
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spi_master_put(spi_gpio->bitbang.master);
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platform_set_drvdata(pdev, NULL);
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gpio_free(SPI_MISO_GPIO);
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gpio_free(SPI_MOSI_GPIO);
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gpio_free(SPI_SCK_GPIO);
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return status;
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}
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MODULE_ALIAS("platform:" DRIVER_NAME);
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static struct platform_driver spi_gpio_driver = {
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.driver.name = DRIVER_NAME,
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.driver.owner = THIS_MODULE,
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.remove = __exit_p(spi_gpio_remove),
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};
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static int __init spi_gpio_init(void)
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{
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return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe);
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}
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module_init(spi_gpio_init);
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static void __exit spi_gpio_exit(void)
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{
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platform_driver_unregister(&spi_gpio_driver);
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}
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module_exit(spi_gpio_exit);
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MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
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MODULE_AUTHOR("David Brownell");
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MODULE_LICENSE("GPL");
|
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|
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@ -0,0 +1,60 @@
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#ifndef __LINUX_SPI_GPIO_H
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#define __LINUX_SPI_GPIO_H
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/*
|
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* For each bitbanged SPI bus, set up a platform_device node with:
|
||||
* - name "spi_gpio"
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* - id the same as the SPI bus number it implements
|
||||
* - dev.platform data pointing to a struct spi_gpio_platform_data
|
||||
*
|
||||
* Or, see the driver code for information about speedups that are
|
||||
* possible on platforms that support inlined access for GPIOs (no
|
||||
* spi_gpio_platform_data is used).
|
||||
*
|
||||
* Use spi_board_info with these busses in the usual way, being sure
|
||||
* that the controller_data being the GPIO used for each device's
|
||||
* chipselect:
|
||||
*
|
||||
* static struct spi_board_info ... [] = {
|
||||
* ...
|
||||
* // this slave uses GPIO 42 for its chipselect
|
||||
* .controller_data = (void *) 42,
|
||||
* ...
|
||||
* // this one uses GPIO 86 for its chipselect
|
||||
* .controller_data = (void *) 86,
|
||||
* ...
|
||||
* };
|
||||
*
|
||||
* If the bitbanged bus is later switched to a "native" controller,
|
||||
* that platform_device and controller_data should be removed.
|
||||
*/
|
||||
|
||||
/**
|
||||
* struct spi_gpio_platform_data - parameter for bitbanged SPI master
|
||||
* @sck: number of the GPIO used for clock output
|
||||
* @mosi: number of the GPIO used for Master Output, Slave In (MOSI) data
|
||||
* @miso: number of the GPIO used for Master Input, Slave Output (MISO) data
|
||||
* @num_chipselect: how many slaves to allow
|
||||
*
|
||||
* All GPIO signals used with the SPI bus managed through this driver
|
||||
* (chipselects, MOSI, MISO, SCK) must be configured as GPIOs, instead
|
||||
* of some alternate function.
|
||||
*
|
||||
* It can be convenient to use this driver with pins that have alternate
|
||||
* functions associated with a "native" SPI controller if a driver for that
|
||||
* controller is not available, or is missing important functionality.
|
||||
*
|
||||
* On platforms which can do so, configure MISO with a weak pullup unless
|
||||
* there's an external pullup on that signal. That saves power by avoiding
|
||||
* floating signals. (A weak pulldown would save power too, but many
|
||||
* drivers expect to see all-ones data as the no slave "response".)
|
||||
*/
|
||||
struct spi_gpio_platform_data {
|
||||
unsigned sck;
|
||||
unsigned mosi;
|
||||
unsigned miso;
|
||||
|
||||
u16 num_chipselect;
|
||||
};
|
||||
|
||||
#endif /* __LINUX_SPI_GPIO_H */
|
||||
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