From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Packham Subject: [PATCH v5 2/2] spi: Add generic SPI multiplexer Date: Tue, 4 Feb 2020 16:28:38 +1300 Message-ID: <20200204032838.20739-3-chris.packham@alliedtelesis.co.nz> References: <20200204032838.20739-1-chris.packham@alliedtelesis.co.nz> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Cc: linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Packham To: broonie@kernel.org, robh+dt@kernel.org, mark.rutland@arm.com, Andy Shevchenko Return-path: In-Reply-To: <20200204032838.20739-1-chris.packham@alliedtelesis.co.nz> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org 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 --- Notes: Changes in v5: - Drop redudnant lines, use IS_ERR() instead of PTR_ERR_OR_ZERO =20 Changes in v4: - incorporate review feedback from Andy drivers/spi/Kconfig | 11 +++ drivers/spi/Makefile | 1 + drivers/spi/spi-mux.c | 187 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 199 insertions(+) create mode 100644 drivers/spi/spi-mux.c diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig index 870f7797b56b..a4509000a291 100644 --- a/drivers/spi/Kconfig +++ b/drivers/spi/Kconfig @@ -881,6 +881,17 @@ config SPI_ZYNQMP_GQSPI # Add new SPI master controllers in alphabetical order above this line # =20 +comment "SPI Multiplexer support" + +config SPI_MUX + tristate "SPI multiplexer support" + select MULTIPLEXER + help + This adds support for SPI multiplexers. Each SPI mux will be + accessible as a SPI controller, the devices behind the mux will appea= r + to be chip selects on this controller. It is still necessary to + select one or more specific mux-controller drivers. + # # There are lots of SPI device types, with sensors and memory # being probably the most widely used ones. diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile index bb49c9e6d0a0..116409533727 100644 --- a/drivers/spi/Makefile +++ b/drivers/spi/Makefile @@ -9,6 +9,7 @@ ccflags-$(CONFIG_SPI_DEBUG) :=3D -DDEBUG # config declarations into driver model code obj-$(CONFIG_SPI_MASTER) +=3D spi.o obj-$(CONFIG_SPI_MEM) +=3D spi-mem.o +obj-$(CONFIG_SPI_MUX) +=3D spi-mux.o obj-$(CONFIG_SPI_SPIDEV) +=3D spidev.o obj-$(CONFIG_SPI_LOOPBACK_TEST) +=3D spi-loopback-test.o =20 diff --git a/drivers/spi/spi-mux.c b/drivers/spi/spi-mux.c new file mode 100644 index 000000000000..4f94c9127fc1 --- /dev/null +++ b/drivers/spi/spi-mux.c @@ -0,0 +1,187 @@ +// SPDX-License-Identifier: GPL-2.0 +// +// General Purpose SPI multiplexer + +#include +#include +#include +#include +#include +#include + +#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 un= der 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 ch= ild'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 =3D spi_controller_get_devdata(spi->controlle= r); + int ret; + + if (priv->current_cs =3D=3D 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 =3D spi->max_speed_hz; + priv->spi->mode =3D spi->mode; + priv->spi->bits_per_word =3D spi->bits_per_word; + + ret =3D mux_control_select(priv->mux, spi->chip_select); + if (ret) + return ret; + + priv->current_cs =3D spi->chip_select; + + return 0; +} + +static int spi_mux_setup(struct spi_device *spi) +{ + struct spi_mux_priv *priv =3D spi_controller_get_devdata(spi->controlle= r); + + /* + * 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 =3D (struct spi_mux_priv *)context; + struct spi_controller *ctlr =3D spi_get_drvdata(priv->spi); + struct spi_message *m =3D ctlr->cur_msg; + + m->complete =3D priv->child_msg_complete; + m->context =3D priv->child_msg_context; + m->spi =3D 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 =3D spi_controller_get_devdata(ctlr); + struct spi_device *spi =3D m->spi; + int ret; + + ret =3D 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 =3D m->complete; + priv->child_msg_context =3D m->context; + priv->child_msg_dev =3D m->spi; + + m->complete =3D spi_mux_complete_cb; + m->context =3D priv; + m->spi =3D 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 =3D spi_alloc_master(&spi->dev, sizeof(*priv)); + if (!ctlr) + return -ENOMEM; + + spi_set_drvdata(spi, ctlr); + priv =3D spi_controller_get_devdata(ctlr); + priv->spi =3D spi; + + priv->mux =3D devm_mux_control_get(&spi->dev, NULL); + if (IS_ERR(priv->mux)) { + ret =3D PTR_ERR(priv->mux); + if (ret !=3D -EPROBE_DEFER) + dev_err(&spi->dev, "failed to get control-mux\n"); + goto err_put_ctlr; + } + + priv->current_cs =3D SPI_MUX_NO_CS; + + /* supported modes are the same as our parent's */ + ctlr->mode_bits =3D spi->controller->mode_bits; + ctlr->flags =3D spi->controller->flags; + ctlr->transfer_one_message =3D spi_mux_transfer_one_message; + ctlr->setup =3D spi_mux_setup; + ctlr->num_chipselect =3D mux_control_states(priv->mux); + ctlr->bus_num =3D -1; + ctlr->dev.of_node =3D spi->dev.of_node; + + ret =3D 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 of_device_id spi_mux_of_match[] =3D { + { .compatible =3D "spi-mux" }, + { } +}; + +static struct spi_driver spi_mux_driver =3D { + .probe =3D spi_mux_probe, + .driver =3D { + .name =3D "spi-mux", + .of_match_table =3D spi_mux_of_match, + }, +}; + +module_spi_driver(spi_mux_driver); + +MODULE_DESCRIPTION("SPI multiplexer"); +MODULE_LICENSE("GPL"); --=20 2.25.0