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Add a SPI device driver that sits in-band and provides a SPI controller which supports chip selects via a mux-control. This enables extra SPI devices to be connected with limited native chip selects. Signed-off-by: Chris Packham <[email protected]> Reviewed-by: Andy Shevchenko <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Mark Brown <[email protected]>
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// SPDX-License-Identifier: GPL-2.0 | ||
// | ||
// General Purpose SPI multiplexer | ||
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#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> | ||
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#define SPI_MUX_NO_CS ((unsigned int)-1) | ||
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/** | ||
* 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. | ||
*/ | ||
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/** | ||
* 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; | ||
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void (*child_msg_complete)(void *context); | ||
void *child_msg_context; | ||
struct spi_device *child_msg_dev; | ||
struct mux_control *mux; | ||
}; | ||
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/* 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; | ||
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if (priv->current_cs == spi->chip_select) | ||
return 0; | ||
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dev_dbg(&priv->spi->dev, "setting up the mux for cs %d\n", | ||
spi->chip_select); | ||
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/* 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; | ||
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ret = mux_control_select(priv->mux, spi->chip_select); | ||
if (ret) | ||
return ret; | ||
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priv->current_cs = spi->chip_select; | ||
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return 0; | ||
} | ||
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static int spi_mux_setup(struct spi_device *spi) | ||
{ | ||
struct spi_mux_priv *priv = spi_controller_get_devdata(spi->controller); | ||
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/* | ||
* 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); | ||
} | ||
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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; | ||
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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); | ||
} | ||
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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; | ||
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ret = spi_mux_select(spi); | ||
if (ret) | ||
return ret; | ||
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/* | ||
* 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; | ||
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m->complete = spi_mux_complete_cb; | ||
m->context = priv; | ||
m->spi = priv->spi; | ||
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/* do the transfer */ | ||
return spi_async(priv->spi, m); | ||
} | ||
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static int spi_mux_probe(struct spi_device *spi) | ||
{ | ||
struct spi_controller *ctlr; | ||
struct spi_mux_priv *priv; | ||
int ret; | ||
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ctlr = spi_alloc_master(&spi->dev, sizeof(*priv)); | ||
if (!ctlr) | ||
return -ENOMEM; | ||
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spi_set_drvdata(spi, ctlr); | ||
priv = spi_controller_get_devdata(ctlr); | ||
priv->spi = spi; | ||
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priv->mux = devm_mux_control_get(&spi->dev, NULL); | ||
if (IS_ERR(priv->mux)) { | ||
ret = PTR_ERR(priv->mux); | ||
if (ret != -EPROBE_DEFER) | ||
dev_err(&spi->dev, "failed to get control-mux\n"); | ||
goto err_put_ctlr; | ||
} | ||
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priv->current_cs = SPI_MUX_NO_CS; | ||
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/* 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; | ||
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ret = devm_spi_register_controller(&spi->dev, ctlr); | ||
if (ret) | ||
goto err_put_ctlr; | ||
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return 0; | ||
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err_put_ctlr: | ||
spi_controller_put(ctlr); | ||
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return ret; | ||
} | ||
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static const struct of_device_id spi_mux_of_match[] = { | ||
{ .compatible = "spi-mux" }, | ||
{ } | ||
}; | ||
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static struct spi_driver spi_mux_driver = { | ||
.probe = spi_mux_probe, | ||
.driver = { | ||
.name = "spi-mux", | ||
.of_match_table = spi_mux_of_match, | ||
}, | ||
}; | ||
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module_spi_driver(spi_mux_driver); | ||
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MODULE_DESCRIPTION("SPI multiplexer"); | ||
MODULE_LICENSE("GPL"); |