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547 lines
15 KiB
C
547 lines
15 KiB
C
/*
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* 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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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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#include <linux/gpio.h>
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#include <linux/of.h>
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#include <linux/of_device.h>
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#include <linux/of_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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unsigned long cs_gpios[0];
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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 struct spi_gpio *__pure
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spi_to_spi_gpio(const struct spi_device *spi)
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{
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const struct spi_bitbang *bang;
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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;
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}
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static inline 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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return &spi_to_spi_gpio(spi)->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_cansleep(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_cansleep(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_cansleep(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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struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
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unsigned long cs = spi_gpio->cs_gpios[spi->chip_select];
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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_cansleep(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;
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int status = 0;
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struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
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struct device_node *np = spi->master->dev.of_node;
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if (np) {
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/*
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* In DT environments, the CS GPIOs have already been
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* initialized from the "cs-gpios" property of the node.
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*/
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cs = spi_gpio->cs_gpios[spi->chip_select];
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} else {
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/*
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* ... otherwise, take it from spi->controller_data
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*/
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cs = (uintptr_t) spi->controller_data;
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}
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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,
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!(spi->mode & SPI_CS_HIGH));
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}
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}
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if (!status) {
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/* in case it was initialized from static board data */
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spi_gpio->cs_gpios[spi->chip_select] = cs;
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status = spi_bitbang_setup(spi);
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}
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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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struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
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unsigned long cs = spi_gpio->cs_gpios[spi->chip_select];
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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 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 spi_gpio_request(struct spi_gpio_platform_data *pdata,
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const char *label, 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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#ifdef CONFIG_OF
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static const struct of_device_id spi_gpio_dt_ids[] = {
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{ .compatible = "spi-gpio" },
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{}
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};
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MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids);
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static int spi_gpio_probe_dt(struct platform_device *pdev)
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{
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int ret;
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u32 tmp;
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struct spi_gpio_platform_data *pdata;
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struct device_node *np = pdev->dev.of_node;
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const struct of_device_id *of_id =
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of_match_device(spi_gpio_dt_ids, &pdev->dev);
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if (!of_id)
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return 0;
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pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
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if (!pdata)
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return -ENOMEM;
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ret = of_get_named_gpio(np, "gpio-sck", 0);
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if (ret < 0) {
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dev_err(&pdev->dev, "gpio-sck property not found\n");
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goto error_free;
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}
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pdata->sck = ret;
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ret = of_get_named_gpio(np, "gpio-miso", 0);
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if (ret < 0) {
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dev_info(&pdev->dev, "gpio-miso property not found, switching to no-rx mode\n");
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pdata->miso = SPI_GPIO_NO_MISO;
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} else
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pdata->miso = ret;
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ret = of_get_named_gpio(np, "gpio-mosi", 0);
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if (ret < 0) {
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dev_info(&pdev->dev, "gpio-mosi property not found, switching to no-tx mode\n");
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pdata->mosi = SPI_GPIO_NO_MOSI;
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} else
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pdata->mosi = ret;
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ret = of_property_read_u32(np, "num-chipselects", &tmp);
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if (ret < 0) {
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dev_err(&pdev->dev, "num-chipselects property not found\n");
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goto error_free;
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}
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pdata->num_chipselect = tmp;
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pdev->dev.platform_data = pdata;
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return 1;
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error_free:
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devm_kfree(&pdev->dev, pdata);
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return ret;
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}
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#else
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static inline int spi_gpio_probe_dt(struct platform_device *pdev)
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{
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return 0;
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}
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#endif
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static int 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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bool use_of = 0;
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int num_devices;
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status = spi_gpio_probe_dt(pdev);
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if (status < 0)
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return status;
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if (status > 0)
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use_of = 1;
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pdata = dev_get_platdata(&pdev->dev);
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#ifdef GENERIC_BITBANG
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if (!pdata || (!use_of && !pdata->num_chipselect))
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return -ENODEV;
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#endif
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if (use_of && !SPI_N_CHIPSEL)
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num_devices = 1;
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else
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num_devices = SPI_N_CHIPSEL;
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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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(sizeof(unsigned long) * num_devices));
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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->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
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master->flags = master_flags;
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master->bus_num = pdev->id;
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master->num_chipselect = num_devices;
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master->setup = spi_gpio_setup;
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master->cleanup = spi_gpio_cleanup;
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#ifdef CONFIG_OF
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master->dev.of_node = pdev->dev.of_node;
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if (use_of) {
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int i;
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struct device_node *np = pdev->dev.of_node;
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/*
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* In DT environments, take the CS GPIO from the "cs-gpios"
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* property of the node.
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*/
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if (!SPI_N_CHIPSEL)
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spi_gpio->cs_gpios[0] = SPI_GPIO_NO_CHIPSELECT;
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else
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for (i = 0; i < SPI_N_CHIPSEL; i++) {
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status = of_get_named_gpio(np, "cs-gpios", i);
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if (status < 0) {
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dev_err(&pdev->dev,
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"invalid cs-gpios property\n");
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goto gpio_free;
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}
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spi_gpio->cs_gpios[i] = status;
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}
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}
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#endif
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spi_gpio->bitbang.master = master;
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spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
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if ((master_flags & (SPI_MASTER_NO_TX | 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;
|
|
spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
|
|
}
|
|
spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
|
|
spi_gpio->bitbang.flags = SPI_CS_HIGH;
|
|
|
|
status = spi_bitbang_start(&spi_gpio->bitbang);
|
|
if (status < 0) {
|
|
gpio_free:
|
|
if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
|
|
gpio_free(SPI_MISO_GPIO);
|
|
if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
|
|
gpio_free(SPI_MOSI_GPIO);
|
|
gpio_free(SPI_SCK_GPIO);
|
|
spi_master_put(master);
|
|
}
|
|
|
|
return status;
|
|
}
|
|
|
|
static int spi_gpio_remove(struct platform_device *pdev)
|
|
{
|
|
struct spi_gpio *spi_gpio;
|
|
struct spi_gpio_platform_data *pdata;
|
|
|
|
spi_gpio = platform_get_drvdata(pdev);
|
|
pdata = dev_get_platdata(&pdev->dev);
|
|
|
|
/* stop() unregisters child devices too */
|
|
spi_bitbang_stop(&spi_gpio->bitbang);
|
|
|
|
if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
|
|
gpio_free(SPI_MISO_GPIO);
|
|
if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
|
|
gpio_free(SPI_MOSI_GPIO);
|
|
gpio_free(SPI_SCK_GPIO);
|
|
spi_master_put(spi_gpio->bitbang.master);
|
|
|
|
return 0;
|
|
}
|
|
|
|
MODULE_ALIAS("platform:" DRIVER_NAME);
|
|
|
|
static struct platform_driver spi_gpio_driver = {
|
|
.driver = {
|
|
.name = DRIVER_NAME,
|
|
.of_match_table = of_match_ptr(spi_gpio_dt_ids),
|
|
},
|
|
.probe = spi_gpio_probe,
|
|
.remove = spi_gpio_remove,
|
|
};
|
|
module_platform_driver(spi_gpio_driver);
|
|
|
|
MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
|
|
MODULE_AUTHOR("David Brownell");
|
|
MODULE_LICENSE("GPL");
|