188 строки
4.8 KiB
C
188 строки
4.8 KiB
C
// 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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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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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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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 = PTR_ERR(priv->mux);
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if (ret != -EPROBE_DEFER)
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dev_err(&spi->dev, "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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