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