diff options
Diffstat (limited to 'drivers/spi/spi-mux.c')
| -rw-r--r-- | drivers/spi/spi-mux.c | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/drivers/spi/spi-mux.c b/drivers/spi/spi-mux.c new file mode 100644 index 000000000..0709e987b --- /dev/null +++ b/drivers/spi/spi-mux.c @@ -0,0 +1,202 @@ +// SPDX-License-Identifier: GPL-2.0 +// +// General Purpose SPI multiplexer + +#include <linux/err.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/mux/consumer.h> +#include <linux/slab.h> +#include <linux/spi/spi.h> + +#define SPI_MUX_NO_CS ((unsigned int)-1) + +/** + * DOC: Driver description + * + * This driver supports a MUX on an SPI bus. This can be useful when you need + * more chip selects than the hardware peripherals support, or than are + * available in a particular board setup. + * + * The driver will create an additional SPI controller. Devices added under the + * mux will be handled as 'chip selects' on this controller. + */ + +/** + * struct spi_mux_priv - the basic spi_mux structure + * @spi: pointer to the device struct attached to the parent + * spi controller + * @current_cs: The current chip select set in the mux + * @child_msg_complete: The mux replaces the complete callback in the child's + * message to its own callback; this field is used by the + * driver to store the child's callback during a transfer + * @child_msg_context: Used to store the child's context to the callback + * @child_msg_dev: Used to store the spi_device pointer to the child + * @mux: mux_control structure used to provide chip selects for + * downstream spi devices + */ +struct spi_mux_priv { + struct spi_device *spi; + unsigned int current_cs; + + void (*child_msg_complete)(void *context); + void *child_msg_context; + struct spi_device *child_msg_dev; + struct mux_control *mux; +}; + +/* should not get called when the parent controller is doing a transfer */ +static int spi_mux_select(struct spi_device *spi) +{ + struct spi_mux_priv *priv = spi_controller_get_devdata(spi->controller); + int ret; + + ret = mux_control_select(priv->mux, spi->chip_select); + if (ret) + return ret; + + if (priv->current_cs == spi->chip_select) + return 0; + + dev_dbg(&priv->spi->dev, "setting up the mux for cs %d\n", + spi->chip_select); + + /* copy the child device's settings except for the cs */ + priv->spi->max_speed_hz = spi->max_speed_hz; + priv->spi->mode = spi->mode; + priv->spi->bits_per_word = spi->bits_per_word; + + priv->current_cs = spi->chip_select; + + return 0; +} + +static int spi_mux_setup(struct spi_device *spi) +{ + struct spi_mux_priv *priv = spi_controller_get_devdata(spi->controller); + + /* + * can be called multiple times, won't do a valid setup now but we will + * change the settings when we do a transfer (necessary because we + * can't predict from which device it will be anyway) + */ + return spi_setup(priv->spi); +} + +static void spi_mux_complete_cb(void *context) +{ + struct spi_mux_priv *priv = (struct spi_mux_priv *)context; + struct spi_controller *ctlr = spi_get_drvdata(priv->spi); + struct spi_message *m = ctlr->cur_msg; + + m->complete = priv->child_msg_complete; + m->context = priv->child_msg_context; + m->spi = priv->child_msg_dev; + spi_finalize_current_message(ctlr); + mux_control_deselect(priv->mux); +} + +static int spi_mux_transfer_one_message(struct spi_controller *ctlr, + struct spi_message *m) +{ + struct spi_mux_priv *priv = spi_controller_get_devdata(ctlr); + struct spi_device *spi = m->spi; + int ret; + + ret = spi_mux_select(spi); + if (ret) + return ret; + + /* + * Replace the complete callback, context and spi_device with our own + * pointers. Save originals + */ + priv->child_msg_complete = m->complete; + priv->child_msg_context = m->context; + priv->child_msg_dev = m->spi; + + m->complete = spi_mux_complete_cb; + m->context = priv; + m->spi = priv->spi; + + /* do the transfer */ + return spi_async(priv->spi, m); +} + +static int spi_mux_probe(struct spi_device *spi) +{ + struct spi_controller *ctlr; + struct spi_mux_priv *priv; + int ret; + + ctlr = spi_alloc_master(&spi->dev, sizeof(*priv)); + if (!ctlr) + return -ENOMEM; + + spi_set_drvdata(spi, ctlr); + priv = spi_controller_get_devdata(ctlr); + priv->spi = spi; + + /* + * Increase lockdep class as these lock are taken while the parent bus + * already holds their instance's lock. + */ + lockdep_set_subclass(&ctlr->io_mutex, 1); + lockdep_set_subclass(&ctlr->add_lock, 1); + + priv->mux = devm_mux_control_get(&spi->dev, NULL); + if (IS_ERR(priv->mux)) { + ret = dev_err_probe(&spi->dev, PTR_ERR(priv->mux), + "failed to get control-mux\n"); + goto err_put_ctlr; + } + + priv->current_cs = SPI_MUX_NO_CS; + + /* supported modes are the same as our parent's */ + ctlr->mode_bits = spi->controller->mode_bits; + ctlr->flags = spi->controller->flags; + ctlr->transfer_one_message = spi_mux_transfer_one_message; + ctlr->setup = spi_mux_setup; + ctlr->num_chipselect = mux_control_states(priv->mux); + ctlr->bus_num = -1; + ctlr->dev.of_node = spi->dev.of_node; + ctlr->must_async = true; + + ret = devm_spi_register_controller(&spi->dev, ctlr); + if (ret) + goto err_put_ctlr; + + return 0; + +err_put_ctlr: + spi_controller_put(ctlr); + + return ret; +} + +static const struct spi_device_id spi_mux_id[] = { + { "spi-mux" }, + { } +}; +MODULE_DEVICE_TABLE(spi, spi_mux_id); + +static const struct of_device_id spi_mux_of_match[] = { + { .compatible = "spi-mux" }, + { } +}; +MODULE_DEVICE_TABLE(of, spi_mux_of_match); + +static struct spi_driver spi_mux_driver = { + .probe = spi_mux_probe, + .driver = { + .name = "spi-mux", + .of_match_table = spi_mux_of_match, + }, + .id_table = spi_mux_id, +}; + +module_spi_driver(spi_mux_driver); + +MODULE_DESCRIPTION("SPI multiplexer"); +MODULE_LICENSE("GPL"); |