From: Jiada Wang <[email protected]> Add support for SPI bus controller to work in slave mode using the existing SPI master framework. - SPI device on SPI bus controller with 'spi-slave' property declared in DT node represents SPI controller itself to work as a slave device and listening to external SPI master devices - when SPI bus controller works in slave mode, 'chip_select' and 'max_speed_hz' are not required. - SPI slave mode continue to use 'struct spi_master'
Signed-off-by: Jiada Wang <[email protected]> --- Documentation/devicetree/bindings/spi/spi-bus.txt | 27 ++++++++++++++--------- Documentation/spi/spi-summary | 19 +++++++++++----- drivers/spi/Kconfig | 14 +++++++++++- drivers/spi/spi.c | 23 ++++++++++++++++++- include/linux/spi/spi.h | 15 +++++++++++++ 5 files changed, 80 insertions(+), 18 deletions(-) diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt index 4b1d6e7..96e93ba 100644 --- a/Documentation/devicetree/bindings/spi/spi-bus.txt +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt @@ -1,17 +1,20 @@ SPI (Serial Peripheral Interface) busses -SPI busses can be described with a node for the SPI master device -and a set of child nodes for each SPI slave on the bus. For this -discussion, it is assumed that the system's SPI controller is in -SPI master mode. This binding does not describe SPI controllers -in slave mode. +SPI busses can be described with a node for the SPI controller device +and a set of child nodes for each SPI slave on the bus. The system's SPI +controller can work either in master mode or in slave mode, based on the +child node on it. -The SPI master node requires the following properties: +The SPI controller node requires the following properties: +- compatible - name of SPI bus controller following generic names + recommended practice. + +In master mode, the SPI controller node requires the following additional +properties: - #address-cells - number of cells required to define a chip select address on the SPI bus. - #size-cells - should be zero. -- compatible - name of SPI bus controller following generic names - recommended practice. + No other properties are required in the SPI bus node. It is assumed that a driver for an SPI bus device will understand that it is an SPI bus. However, the binding does not attempt to define the specific method for @@ -43,10 +46,11 @@ cs3 : &gpio1 2 0 SPI slave nodes must be children of the SPI master node and can contain the following properties. -- reg - (required) chip select address of device. +- reg - (required, master mode only) chip select address of device. - compatible - (required) name of SPI device following generic names recommended practice. -- spi-max-frequency - (required) Maximum SPI clocking speed of device in Hz. +- spi-max-frequency - (required, master mode only) Maximum SPI clocking speed of + device in Hz. - spi-cpol - (optional) Empty property indicating device requires inverse clock polarity (CPOL) mode. - spi-cpha - (optional) Empty property indicating device requires @@ -63,6 +67,9 @@ contain the following properties. used for MISO. Defaults to 1 if not present. - spi-rx-delay-us - (optional) Microsecond delay after a read transfer. - spi-tx-delay-us - (optional) Microsecond delay after a write transfer. +- spi-slave - (optional) Empty property indicating SPI bus controller + itself works in slave mode to interface with external master + devices. Some SPI controllers and devices support Dual and Quad SPI transfer mode. It allows data in the SPI system to be transferred using 2 wires (DUAL) or 4 diff --git a/Documentation/spi/spi-summary b/Documentation/spi/spi-summary index d1824b3..4c2ceaa 100644 --- a/Documentation/spi/spi-summary +++ b/Documentation/spi/spi-summary @@ -62,9 +62,8 @@ chips described as using "three wire" signaling: SCK, data, nCSx. (That data line is sometimes called MOMI or SISO.) Microcontrollers often support both master and slave sides of the SPI -protocol. This document (and Linux) currently only supports the master -side of SPI interactions. - +protocol. This document (and Linux) supports both the master and slave +sides of SPI interactions. Who uses it? On what kinds of systems? --------------------------------------- @@ -154,9 +153,8 @@ control audio interfaces, present touchscreen sensors as input interfaces, or monitor temperature and voltage levels during industrial processing. And those might all be sharing the same controller driver. -A "struct spi_device" encapsulates the master-side interface between -those two types of driver. At this writing, Linux has no slave side -programming interface. +A "struct spi_device" encapsulates the controller-side interface between +those two types of drivers. There is a minimal core of SPI programming interfaces, focussing on using the driver model to connect controller and protocol drivers using @@ -168,12 +166,21 @@ shows up in sysfs in several locations: /sys/devices/.../CTLR/spiB.C ... spi_device on bus "B", chipselect C, accessed through CTLR. + /sys/devices/.../CTLR/spiB-slv ... SPI bus "B" controller itself as a + spi_device works in slave mode, accessed through CTRL. + /sys/bus/spi/devices/spiB.C ... symlink to that physical .../CTLR/spiB.C device + /sys/bus/spi/devices/spiB-slv ... symlink to that physical + .../CTLR/spiB-slv device + /sys/devices/.../CTLR/spiB.C/modalias ... identifies the driver that should be used with this device (for hotplug/coldplug) + /sys/devices/.../CTLR/spiB-slv/modalias ... identifies the driver + that should be used with this device (for hotplug/coldplug) + /sys/bus/spi/drivers/D ... driver for one or more spi*.* devices /sys/class/spi_master/spiB ... symlink (or actual device node) to diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig index 25ae7f2e..1096c7d 100644 --- a/drivers/spi/Kconfig +++ b/drivers/spi/Kconfig @@ -784,6 +784,18 @@ config SPI_TLE62X0 endif # SPI_MASTER -# (slave support would go here) +# +# SLAVE side ... listening to other SPI masters +# + +config SPI_SLAVE + bool "SPI slave protocol handlers" + help + If your system has a slave-capable SPI controller, you can enable + slave protocol handlers. + +if SPI_SLAVE + +endif # SPI_SLAVE endif # SPI diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 90b5b2e..3af26e2 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -475,6 +475,12 @@ static void spi_dev_set_name(struct spi_device *spi) return; } + if (spi->slave_mode) { + dev_set_name(&spi->dev, "%s-slv", + dev_name(&spi->master->dev)); + return; + } + dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->master->dev), spi->chip_select); } @@ -484,6 +490,9 @@ static int spi_dev_check(struct device *dev, void *data) struct spi_device *spi = to_spi_device(dev); struct spi_device *new_spi = data; + if (spi->slave_mode) + return 0; + if (spi->master == new_spi->master && spi->chip_select == new_spi->chip_select) return -EBUSY; @@ -523,6 +532,9 @@ int spi_add_device(struct spi_device *spi) */ mutex_lock(&spi_add_lock); + if (spi->slave_mode) + goto setup_spi; + status = bus_for_each_dev(&spi_bus_type, NULL, spi, spi_dev_check); if (status) { dev_err(dev, "chipselect %d already in use\n", @@ -533,6 +545,7 @@ int spi_add_device(struct spi_device *spi) if (master->cs_gpios) spi->cs_gpio = master->cs_gpios[spi->chip_select]; +setup_spi: /* Drivers may modify this initial i/o setup, but will * normally rely on the device being setup. Devices * using SPI_CS_HIGH can't coexist well otherwise... @@ -1511,6 +1524,14 @@ static int of_spi_parse_dt(struct spi_master *master, struct spi_device *spi, u32 value; int rc; + if (of_find_property(nc, "spi-slave", NULL)) { + if (!spi_controller_has_slavemode(master)) + return -EINVAL; + + spi->slave_mode = 1; + return 0; + } + /* Device address */ rc = of_property_read_u32(nc, "reg", &value); if (rc) { @@ -1961,7 +1982,7 @@ int spi_register_master(struct spi_master *master) status = device_add(&master->dev); if (status < 0) goto done; - dev_dbg(dev, "registered master %s%s\n", dev_name(&master->dev), + dev_dbg(dev, "registered controller %s%s\n", dev_name(&master->dev), dynamic ? " (dynamic)" : ""); /* If we're using a queued driver, start the queue */ diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 75c6bd0..bb81425 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -115,6 +115,8 @@ void spi_statistics_add_transfer_stats(struct spi_statistics *stats, * This may be changed by the device's driver, or left at the * default (0) indicating protocol words are eight bit bytes. * The spi_transfer.bits_per_word can override this for each transfer. + * @slave_mode: indicates whether SPI controller works in master mode + * or slave mode to transfer data with external spi devices. * @irq: Negative, or the number passed to request_irq() to receive * interrupts from this device. * @controller_state: Controller's runtime state @@ -144,6 +146,7 @@ struct spi_device { u8 chip_select; u8 bits_per_word; u16 mode; + u8 slave_mode; #define SPI_CPHA 0x01 /* clock phase */ #define SPI_CPOL 0x02 /* clock polarity */ #define SPI_MODE_0 (0|0) /* (original MicroWire) */ @@ -372,6 +375,7 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv) * transfer_one callback. * @handle_err: the subsystem calls the driver to handle an error that occurs * in the generic implementation of transfer_one_message(). + * @has_slavemode: checks whether SPI Controller supports slave mode or not. * @unprepare_message: undo any work done by prepare_message(). * @spi_flash_read: to support spi-controller hardwares that provide * accelerated interface to read from flash devices. @@ -549,6 +553,7 @@ struct spi_master { struct spi_transfer *transfer); void (*handle_err)(struct spi_master *master, struct spi_message *message); + bool (*has_slavemode)(struct spi_master *master); /* gpio chip select */ int *cs_gpios; @@ -590,6 +595,16 @@ static inline void spi_master_put(struct spi_master *master) put_device(&master->dev); } + +static inline bool spi_controller_has_slavemode(struct spi_master *master) +{ +#ifdef CONFIG_SPI_SLAVE + if (master->has_slavemode) + return master->has_slavemode(master); +#endif + return false; +} + /* PM calls that need to be issued by the driver */ extern int spi_master_suspend(struct spi_master *master); extern int spi_master_resume(struct spi_master *master); -- 2.7.4
