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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* SPI master driver using generic bitbanged GPIO
*
* Copyright (C) 2006,2008 David Brownell
* Copyright (C) 2017 Linus Walleij
*/
#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->master->dev.driver_data ... points to spi_gpio->bitbang
*/
struct spi_gpio {
struct spi_bitbang bitbang;
struct gpio_desc *sck;
struct gpio_desc *miso;
struct gpio_desc *mosi;
struct gpio_desc **cs_gpios;
};
/*----------------------------------------------------------------------*/
/*
* 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;
}
/* 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->cs_gpios) {
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.
*/
if (spi_gpio->cs_gpios) {
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)
{
spi_gpio->mosi = devm_gpiod_get_optional(dev, "mosi", GPIOD_OUT_LOW);
if (IS_ERR(spi_gpio->mosi))
return PTR_ERR(spi_gpio->mosi);
spi_gpio->miso = devm_gpiod_get_optional(dev, "miso", GPIOD_IN);
if (IS_ERR(spi_gpio->miso))
return
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