diff options
Diffstat (limited to 'drivers/spi/spi.c')
| -rw-r--r-- | drivers/spi/spi.c | 106 |
1 files changed, 92 insertions, 14 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 9da0bc5a036c..6ca59406b0b7 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1,18 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0-or-later /* * SPI init/core code * * Copyright (C) 2005 David Brownell * Copyright (C) 2008 Secret Lab Technologies Ltd. - * - * 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> @@ -60,6 +51,7 @@ static void spidev_release(struct device *dev) spi->controller->cleanup(spi); spi_controller_put(spi->controller); + kfree(spi->driver_override); kfree(spi); } @@ -77,6 +69,51 @@ modalias_show(struct device *dev, struct device_attribute *a, char *buf) } static DEVICE_ATTR_RO(modalias); +static ssize_t driver_override_store(struct device *dev, + struct device_attribute *a, + const char *buf, size_t count) +{ + struct spi_device *spi = to_spi_device(dev); + const char *end = memchr(buf, '\n', count); + const size_t len = end ? end - buf : count; + const char *driver_override, *old; + + /* We need to keep extra room for a newline when displaying value */ + if (len >= (PAGE_SIZE - 1)) + return -EINVAL; + + driver_override = kstrndup(buf, len, GFP_KERNEL); + if (!driver_override) + return -ENOMEM; + + device_lock(dev); + old = spi->driver_override; + if (len) { + spi->driver_override = driver_override; + } else { + /* Emptry string, disable driver override */ + spi->driver_override = NULL; + kfree(driver_override); + } + device_unlock(dev); + kfree(old); + + return count; +} + +static ssize_t driver_override_show(struct device *dev, + struct device_attribute *a, char *buf) +{ + const struct spi_device *spi = to_spi_device(dev); + ssize_t len; + + device_lock(dev); + len = snprintf(buf, PAGE_SIZE, "%s\n", spi->driver_override ? : ""); + device_unlock(dev); + return len; +} +static DEVICE_ATTR_RW(driver_override); + #define SPI_STATISTICS_ATTRS(field, file) \ static ssize_t spi_controller_##field##_show(struct device *dev, \ struct device_attribute *attr, \ @@ -158,6 +195,7 @@ SPI_STATISTICS_SHOW(transfers_split_maxsize, "%lu"); static struct attribute *spi_dev_attrs[] = { &dev_attr_modalias.attr, + &dev_attr_driver_override.attr, NULL, }; @@ -305,6 +343,10 @@ static int spi_match_device(struct device *dev, struct device_driver *drv) const struct spi_device *spi = to_spi_device(dev); const struct spi_driver *sdrv = to_spi_driver(drv); + /* Check override first, and if set, only use the named driver */ + if (spi->driver_override) + return strcmp(spi->driver_override, drv->name) == 0; + /* Attempt an OF style match */ if (of_driver_match_device(dev, drv)) return 1; @@ -733,7 +775,9 @@ static void spi_set_cs(struct spi_device *spi, bool enable) enable = !enable; if (gpio_is_valid(spi->cs_gpio)) { - gpio_set_value(spi->cs_gpio, !enable); + /* Honour the SPI_NO_CS flag */ + if (!(spi->mode & SPI_NO_CS)) + gpio_set_value(spi->cs_gpio, !enable); /* Some SPI masters need both GPIO CS & slave_select */ if ((spi->controller->flags & SPI_MASTER_GPIO_SS) && spi->controller->set_cs) @@ -2783,8 +2827,10 @@ int spi_setup(struct spi_device *spi) return -EINVAL; /* help drivers fail *cleanly* when they need options * that aren't supported with their current controller + * SPI_CS_WORD has a fallback software implementation, + * so it is ignored here. */ - bad_bits = spi->mode & ~spi->controller->mode_bits; + bad_bits = spi->mode & ~(spi->controller->mode_bits | SPI_CS_WORD); ugly_bits = bad_bits & (SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD); if (ugly_bits) { @@ -2838,6 +2884,35 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message) if (list_empty(&message->transfers)) return -EINVAL; + /* If an SPI controller does not support toggling the CS line on each + * transfer (indicated by the SPI_CS_WORD flag) or we are using a GPIO + * for the CS line, we can emulate the CS-per-word hardware function by + * splitting transfers into one-word transfers and ensuring that + * cs_change is set for each transfer. + */ + if ((spi->mode & SPI_CS_WORD) && (!(ctlr->mode_bits & SPI_CS_WORD) || + gpio_is_valid(spi->cs_gpio))) { + size_t maxsize; + int ret; + + maxsize = (spi->bits_per_word + 7) / 8; + + /* spi_split_transfers_maxsize() requires message->spi */ + message->spi = spi; + + ret = spi_split_transfers_maxsize(ctlr, message, maxsize, + GFP_KERNEL); + if (ret) + return ret; + + list_for_each_entry(xfer, &message->transfers, transfer_list) { + /* don't change cs_change on the last entry in the list */ + if (list_is_last(&xfer->transfer_list, &message->transfers)) + break; + xfer->cs_change = 1; + } + } + /* Half-duplex links include original MicroWire, and ones with * only one data pin like SPI_3WIRE (switches direction) or where * either MOSI or MISO is missing. They can also be caused by @@ -3323,20 +3398,23 @@ EXPORT_SYMBOL_GPL(spi_write_then_read); /*-------------------------------------------------------------------------*/ -#if IS_ENABLED(CONFIG_OF_DYNAMIC) +#if IS_ENABLED(CONFIG_OF) static int __spi_of_device_match(struct device *dev, void *data) { return dev->of_node == data; } /* must call put_device() when done with returned spi_device device */ -static struct spi_device *of_find_spi_device_by_node(struct device_node *node) +struct spi_device *of_find_spi_device_by_node(struct device_node *node) { struct device *dev = bus_find_device(&spi_bus_type, NULL, node, __spi_of_device_match); return dev ? to_spi_device(dev) : NULL; } +EXPORT_SYMBOL_GPL(of_find_spi_device_by_node); +#endif /* IS_ENABLED(CONFIG_OF) */ +#if IS_ENABLED(CONFIG_OF_DYNAMIC) static int __spi_of_controller_match(struct device *dev, const void *data) { return dev->of_node == data; |