| /* |
| * SPI master driver using generic bitbanged GPIO |
| * |
| * Copyright (C) 2006,2008 David Brownell |
| * Copyright (C) 2017 Linus Walleij |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| */ |
| #include <linux/kernel.h> |
| #include <linux/module.h> |
| #include <linux/platform_device.h> |
| #include <linux/gpio/consumer.h> |
| #include <linux/of.h> |
| #include <linux/of_device.h> |
| |
| #include <linux/spi/spi.h> |
| #include <linux/spi/spi_bitbang.h> |
| #include <linux/spi/spi_gpio.h> |
| |
| |
| /* |
| * This bitbanging SPI master driver should help make systems usable |
| * when a native hardware SPI engine is not available, perhaps because |
| * its driver isn't yet working or because the I/O pins it requires |
| * are used for other purposes. |
| * |
| * platform_device->driver_data ... points to spi_gpio |
| * |
| * spi->controller_state ... reserved for bitbang framework code |
| * spi->controller_data ... holds chipselect GPIO |
| * |
| * spi->master->dev.driver_data ... points to spi_gpio->bitbang |
| */ |
| |
| struct spi_gpio { |
| struct spi_bitbang bitbang; |
| struct spi_gpio_platform_data pdata; |
| struct platform_device *pdev; |
| struct gpio_desc *sck; |
| struct gpio_desc *miso; |
| struct gpio_desc *mosi; |
| struct gpio_desc **cs_gpios; |
| bool has_cs; |
| }; |
| |
| /*----------------------------------------------------------------------*/ |
| |
| /* |
| * Because the overhead of going through four GPIO procedure calls |
| * per transferred bit can make performance a problem, this code |
| * is set up so that you can use it in either of two ways: |
| * |
| * - The slow generic way: set up platform_data to hold the GPIO |
| * numbers used for MISO/MOSI/SCK, and issue procedure calls for |
| * each of them. This driver can handle several such busses. |
| * |
| * - The quicker inlined way: only helps with platform GPIO code |
| * that inlines operations for constant GPIOs. This can give |
| * you tight (fast!) inner loops, but each such bus needs a |
| * new driver. You'll define a new C file, with Makefile and |
| * Kconfig support; the C code can be a total of six lines: |
| * |
| * #define DRIVER_NAME "myboard_spi2" |
| * #define SPI_MISO_GPIO 119 |
| * #define SPI_MOSI_GPIO 120 |
| * #define SPI_SCK_GPIO 121 |
| * #define SPI_N_CHIPSEL 4 |
| * #include "spi-gpio.c" |
| */ |
| |
| #ifndef DRIVER_NAME |
| #define DRIVER_NAME "spi_gpio" |
| |
| #define GENERIC_BITBANG /* vs tight inlines */ |
| |
| #endif |
| |
| /*----------------------------------------------------------------------*/ |
| |
| static inline struct spi_gpio *__pure |
| spi_to_spi_gpio(const struct spi_device *spi) |
| { |
| const struct spi_bitbang *bang; |
| struct spi_gpio *spi_gpio; |
| |
| bang = spi_master_get_devdata(spi->master); |
| spi_gpio = container_of(bang, struct spi_gpio, bitbang); |
| return spi_gpio; |
| } |
| |
| static inline struct spi_gpio_platform_data *__pure |
| spi_to_pdata(const struct spi_device *spi) |
| { |
| return &spi_to_spi_gpio(spi)->pdata; |
| } |
| |
| /* These helpers are in turn called by the bitbang inlines */ |
| static inline void setsck(const struct spi_device *spi, int is_on) |
| { |
| struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
| |
| gpiod_set_value_cansleep(spi_gpio->sck, is_on); |
| } |
| |
| static inline void setmosi(const struct spi_device *spi, int is_on) |
| { |
| struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
| |
| gpiod_set_value_cansleep(spi_gpio->mosi, is_on); |
| } |
| |
| static inline int getmiso(const struct spi_device *spi) |
| { |
| struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
| |
| if (spi->mode & SPI_3WIRE) |
| return !!gpiod_get_value_cansleep(spi_gpio->mosi); |
| else |
| return !!gpiod_get_value_cansleep(spi_gpio->miso); |
| } |
| |
| /* |
| * NOTE: this clocks "as fast as we can". It "should" be a function of the |
| * requested device clock. Software overhead means we usually have trouble |
| * reaching even one Mbit/sec (except when we can inline bitops), so for now |
| * we'll just assume we never need additional per-bit slowdowns. |
| */ |
| #define spidelay(nsecs) do {} while (0) |
| |
| #include "spi-bitbang-txrx.h" |
| |
| /* |
| * These functions can leverage inline expansion of GPIO calls to shrink |
| * costs for a txrx bit, often by factors of around ten (by instruction |
| * count). That is particularly visible for larger word sizes, but helps |
| * even with default 8-bit words. |
| * |
| * REVISIT overheads calling these functions for each word also have |
| * significant performance costs. Having txrx_bufs() calls that inline |
| * the txrx_word() logic would help performance, e.g. on larger blocks |
| * used with flash storage or MMC/SD. There should also be ways to make |
| * GCC be less stupid about reloading registers inside the I/O loops, |
| * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3? |
| */ |
| |
| static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi, |
| unsigned nsecs, u32 word, u8 bits, unsigned flags) |
| { |
| return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); |
| } |
| |
| static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi, |
| unsigned nsecs, u32 word, u8 bits, unsigned flags) |
| { |
| return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits); |
| } |
| |
| static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi, |
| unsigned nsecs, u32 word, u8 bits, unsigned flags) |
| { |
| return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits); |
| } |
| |
| static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi, |
| unsigned nsecs, u32 word, u8 bits, unsigned flags) |
| { |
| return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits); |
| } |
| |
| /* |
| * These functions do not call setmosi or getmiso if respective flag |
| * (SPI_MASTER_NO_RX or SPI_MASTER_NO_TX) is set, so they are safe to |
| * call when such pin is not present or defined in the controller. |
| * A separate set of callbacks is defined to get highest possible |
| * speed in the generic case (when both MISO and MOSI lines are |
| * available), as optimiser will remove the checks when argument is |
| * constant. |
| */ |
| |
| static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi, |
| unsigned nsecs, u32 word, u8 bits, unsigned flags) |
| { |
| flags = spi->master->flags; |
| return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); |
| } |
| |
| static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi, |
| unsigned nsecs, u32 word, u8 bits, unsigned flags) |
| { |
| flags = spi->master->flags; |
| return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits); |
| } |
| |
| static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi, |
| unsigned nsecs, u32 word, u8 bits, unsigned flags) |
| { |
| flags = spi->master->flags; |
| return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits); |
| } |
| |
| static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi, |
| unsigned nsecs, u32 word, u8 bits, unsigned flags) |
| { |
| flags = spi->master->flags; |
| return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits); |
| } |
| |
| /*----------------------------------------------------------------------*/ |
| |
| static void spi_gpio_chipselect(struct spi_device *spi, int is_active) |
| { |
| struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
| |
| /* set initial clock line level */ |
| if (is_active) |
| gpiod_set_value_cansleep(spi_gpio->sck, spi->mode & SPI_CPOL); |
| |
| /* Drive chip select line, if we have one */ |
| if (spi_gpio->has_cs) { |
| struct gpio_desc *cs = spi_gpio->cs_gpios[spi->chip_select]; |
| |
| /* SPI chip selects are normally active-low */ |
| gpiod_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active); |
| } |
| } |
| |
| static int spi_gpio_setup(struct spi_device *spi) |
| { |
| struct gpio_desc *cs; |
| int status = 0; |
| struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
| |
| /* |
| * The CS GPIOs have already been |
| * initialized from the descriptor lookup. |
| */ |
| cs = spi_gpio->cs_gpios[spi->chip_select]; |
| if (!spi->controller_state && cs) |
| status = gpiod_direction_output(cs, |
| !(spi->mode & SPI_CS_HIGH)); |
| |
| if (!status) |
| status = spi_bitbang_setup(spi); |
| |
| return status; |
| } |
| |
| static int spi_gpio_set_direction(struct spi_device *spi, bool output) |
| { |
| struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
| int ret; |
| |
| if (output) |
| return gpiod_direction_output(spi_gpio->mosi, 1); |
| |
| ret = gpiod_direction_input(spi_gpio->mosi); |
| if (ret) |
| return ret; |
| /* |
| * Send a turnaround high impedance cycle when switching |
| * from output to input. Theoretically there should be |
| * a clock delay here, but as has been noted above, the |
| * nsec delay function for bit-banged GPIO is simply |
| * {} because bit-banging just doesn't get fast enough |
| * anyway. |
| */ |
| if (spi->mode & SPI_3WIRE_HIZ) { |
| gpiod_set_value_cansleep(spi_gpio->sck, |
| !(spi->mode & SPI_CPOL)); |
| gpiod_set_value_cansleep(spi_gpio->sck, |
| !!(spi->mode & SPI_CPOL)); |
| } |
| return 0; |
| } |
| |
| static void spi_gpio_cleanup(struct spi_device *spi) |
| { |
| spi_bitbang_cleanup(spi); |
| } |
| |
| /* |
| * 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".) |
| */ |
| static int spi_gpio_request(struct device *dev, |
| struct spi_gpio *spi_gpio, |
| unsigned int num_chipselects, |
| u16 *mflags) |
| { |
| int i; |
| |
| spi_gpio->mosi = devm_gpiod_get_optional(dev, "mosi", GPIOD_OUT_LOW); |
| if (IS_ERR(spi_gpio->mosi)) |
| return PTR_ERR(spi_gpio->mosi); |
| if (!spi_gpio->mosi) |
| /* HW configuration without MOSI pin */ |
| *mflags |= SPI_MASTER_NO_TX; |
| |
| spi_gpio->miso = devm_gpiod_get_optional(dev, "miso", GPIOD_IN); |
| if (IS_ERR(spi_gpio->miso)) |
| return PTR_ERR(spi_gpio->miso); |
| /* |
| * No setting SPI_MASTER_NO_RX here - if there is only a MOSI |
| * pin connected the host can still do RX by changing the |
| * direction of the line. |
| */ |
| |
| spi_gpio->sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW); |
| if (IS_ERR(spi_gpio->sck)) |
| return PTR_ERR(spi_gpio->sck); |
| |
| for (i = 0; i < num_chipselects; i++) { |
| spi_gpio->cs_gpios[i] = devm_gpiod_get_index(dev, "cs", |
| i, GPIOD_OUT_HIGH); |
| if (IS_ERR(spi_gpio->cs_gpios[i])) |
| return PTR_ERR(spi_gpio->cs_gpios[i]); |
| } |
| |
| return 0; |
| } |
| |
| #ifdef CONFIG_OF |
| static const struct of_device_id spi_gpio_dt_ids[] = { |
| { .compatible = "spi-gpio" }, |
| {} |
| }; |
| MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids); |
| |
| static int spi_gpio_probe_dt(struct platform_device *pdev) |
| { |
| int ret; |
| u32 tmp; |
| struct spi_gpio_platform_data *pdata; |
| struct device_node *np = pdev->dev.of_node; |
| const struct of_device_id *of_id = |
| of_match_device(spi_gpio_dt_ids, &pdev->dev); |
| |
| if (!of_id) |
| return 0; |
| |
| pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL); |
| if (!pdata) |
| return -ENOMEM; |
| |
| |
| ret = of_property_read_u32(np, "num-chipselects", &tmp); |
| if (ret < 0) { |
| dev_err(&pdev->dev, "num-chipselects property not found\n"); |
| goto error_free; |
| } |
| |
| pdata->num_chipselect = tmp; |
| pdev->dev.platform_data = pdata; |
| |
| return 1; |
| |
| error_free: |
| devm_kfree(&pdev->dev, pdata); |
| return ret; |
| } |
| #else |
| static inline int spi_gpio_probe_dt(struct platform_device *pdev) |
| { |
| return 0; |
| } |
| #endif |
| |
| static int spi_gpio_probe(struct platform_device *pdev) |
| { |
| int status; |
| struct spi_master *master; |
| struct spi_gpio *spi_gpio; |
| struct spi_gpio_platform_data *pdata; |
| u16 master_flags = 0; |
| bool use_of = 0; |
| |
| status = spi_gpio_probe_dt(pdev); |
| if (status < 0) |
| return status; |
| if (status > 0) |
| use_of = 1; |
| |
| pdata = dev_get_platdata(&pdev->dev); |
| #ifdef GENERIC_BITBANG |
| if (!pdata || (!use_of && !pdata->num_chipselect)) |
| return -ENODEV; |
| #endif |
| |
| master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio)); |
| if (!master) |
| return -ENOMEM; |
| |
| spi_gpio = spi_master_get_devdata(master); |
| |
| spi_gpio->cs_gpios = devm_kcalloc(&pdev->dev, |
| pdata->num_chipselect, |
| sizeof(*spi_gpio->cs_gpios), |
| GFP_KERNEL); |
| if (!spi_gpio->cs_gpios) |
| return -ENOMEM; |
| |
| platform_set_drvdata(pdev, spi_gpio); |
| |
| /* Determine if we have chip selects connected */ |
| spi_gpio->has_cs = !!pdata->num_chipselect; |
| |
| spi_gpio->pdev = pdev; |
| if (pdata) |
| spi_gpio->pdata = *pdata; |
| |
| status = spi_gpio_request(&pdev->dev, spi_gpio, |
| pdata->num_chipselect, &master_flags); |
| if (status) |
| return status; |
| |
| master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32); |
| master->mode_bits = SPI_3WIRE | SPI_3WIRE_HIZ | SPI_CPHA | SPI_CPOL | |
| SPI_CS_HIGH; |
| master->flags = master_flags; |
| master->bus_num = pdev->id; |
| /* The master needs to think there is a chipselect even if not connected */ |
| master->num_chipselect = spi_gpio->has_cs ? pdata->num_chipselect : 1; |
| master->setup = spi_gpio_setup; |
| master->cleanup = spi_gpio_cleanup; |
| #ifdef CONFIG_OF |
| master->dev.of_node = pdev->dev.of_node; |
| #endif |
| |
| spi_gpio->bitbang.master = master; |
| spi_gpio->bitbang.chipselect = spi_gpio_chipselect; |
| spi_gpio->bitbang.set_line_direction = spi_gpio_set_direction; |
| |
| if ((master_flags & SPI_MASTER_NO_TX) == 0) { |
| spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0; |
| spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1; |
| spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2; |
| spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3; |
| } else { |
| spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0; |
| spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1; |
| 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; |
| |
| status = spi_bitbang_start(&spi_gpio->bitbang); |
| if (status) |
| spi_master_put(master); |
| |
| return status; |
| } |
| |
| static int spi_gpio_remove(struct platform_device *pdev) |
| { |
| struct spi_gpio *spi_gpio; |
| |
| spi_gpio = platform_get_drvdata(pdev); |
| |
| /* stop() unregisters child devices too */ |
| spi_bitbang_stop(&spi_gpio->bitbang); |
| |
| 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"); |