![Marek Szyprowski](/assets/img/avatar_default.png)
There are some boards that do not strictly follow SPI standard and use only 3 wires (SCLK, MOSI or MISO, SS) for connecting some simple auxiliary chips and controls them with GPIO based 'spi controller'. In this configuration the MISO or MOSI line is missing (it is not required if the chip does not transfer any data back to host or host only reads data from chip). This patch adds support for such non-standard configuration in GPIO-based SPI controller. It has been tested in configuration without MISO pin. Reviewed-by: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Acked-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
430 lines
12 KiB
C
430 lines
12 KiB
C
/*
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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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#include "spi_bitbang_txrx.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, 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, 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, 0, 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, 0, word, bits);
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}
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/*
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* These functions do not call setmosi or getmiso if respective flag
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* (SPI_MASTER_NO_RX or SPI_MASTER_NO_TX) is set, so they are safe to
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* call when such pin is not present or defined in the controller.
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* A separate set of callbacks is defined to get highest possible
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* speed in the generic case (when both MISO and MOSI lines are
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* available), as optimiser will remove the checks when argument is
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* constant.
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*/
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static u32 spi_gpio_spec_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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unsigned flags = spi->master->flags;
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return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
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}
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static u32 spi_gpio_spec_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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unsigned flags = spi->master->flags;
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return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits);
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}
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static u32 spi_gpio_spec_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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unsigned flags = spi->master->flags;
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return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits);
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}
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static u32 spi_gpio_spec_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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unsigned flags = spi->master->flags;
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return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, 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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if (cs != SPI_GPIO_NO_CHIPSELECT) {
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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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}
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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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if (cs != SPI_GPIO_NO_CHIPSELECT) {
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status = gpio_request(cs, dev_name(&spi->dev));
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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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}
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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 && cs != SPI_GPIO_NO_CHIPSELECT)
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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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if (cs != SPI_GPIO_NO_CHIPSELECT)
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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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u16 *res_flags)
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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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if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) {
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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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} else {
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/* HW configuration without MOSI pin */
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*res_flags |= SPI_MASTER_NO_TX;
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}
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if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) {
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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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} else {
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/* HW configuration without MISO pin */
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*res_flags |= SPI_MASTER_NO_RX;
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}
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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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if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
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gpio_free(SPI_MISO_GPIO);
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free_mosi:
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if (SPI_MOSI_GPIO != SPI_GPIO_NO_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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u16 master_flags = 0;
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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), &master_flags);
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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->flags = master_flags;
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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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if ((master_flags & (SPI_MASTER_NO_RX | SPI_MASTER_NO_RX)) == 0) {
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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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} else {
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spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0;
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spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1;
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spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2;
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spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
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}
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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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if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
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gpio_free(SPI_MISO_GPIO);
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if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
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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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if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
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gpio_free(SPI_MISO_GPIO);
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if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
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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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