Add an example SPI slave handler to allow remote control of system reboot, power off, halt, and suspend.
Signed-off-by: Geert Uytterhoeven <[email protected]> --- v2: - Use spi_async() instead of spi_read(), - Submit the next transfer from the previous transfer's completion callback, removing the need for a thread, - Let .remove() call spi_slave_abort() to cancel the current ongoing transfer, and wait for the completion to terminate, - Remove FIXME about hanging kthread_stop(), - Fix copy-and-pasted module description. --- drivers/spi/Kconfig | 6 ++ drivers/spi/Makefile | 1 + drivers/spi/spi-slave-system-control.c | 154 +++++++++++++++++++++++++++++++++ 3 files changed, 161 insertions(+) create mode 100644 drivers/spi/spi-slave-system-control.c diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig index 515bddee4018c246..3d8ae9505ef95992 100644 --- a/drivers/spi/Kconfig +++ b/drivers/spi/Kconfig @@ -755,6 +755,12 @@ config SPI_SLAVE_TIME SPI slave handler responding with the time of reception of the last SPI message. +config SPI_SLAVE_SYSTEM_CONTROL + tristate "SPI slave handler controlling system state" + help + SPI slave handler to allow remote control of system reboot, power + off, halt, and suspend. + endif # SPI_SLAVE endif # SPI diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile index ba4a7e79fe113d3e..e402c1a12f47c38f 100644 --- a/drivers/spi/Makefile +++ b/drivers/spi/Makefile @@ -101,3 +101,4 @@ obj-$(CONFIG_SPI_ZYNQMP_GQSPI) += spi-zynqmp-gqspi.o # SPI slave protocol handlers obj-$(CONFIG_SPI_SLAVE_TIME) += spi-slave-time.o +obj-$(CONFIG_SPI_SLAVE_SYSTEM_CONTROL) += spi-slave-system-control.o diff --git a/drivers/spi/spi-slave-system-control.c b/drivers/spi/spi-slave-system-control.c new file mode 100644 index 0000000000000000..736dd59928cb3bc3 --- /dev/null +++ b/drivers/spi/spi-slave-system-control.c @@ -0,0 +1,154 @@ +/* + * SPI slave handler controlling system state + * + * This SPI slave handler allows remote control of system reboot, power off, + * halt, and suspend. + * + * Copyright (C) 2016 Glider bvba + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + */ + +#include <linux/completion.h> +#include <linux/module.h> +#include <linux/reboot.h> +#include <linux/suspend.h> +#include <linux/spi/spi.h> + +/* + * The numbers are chosen to display something human-readable on two 7-segment + * displays connected to two 74HC595 shift registers + */ +#define CMD_REBOOT 0x507c /* rb */ +#define CMD_POWEROFF 0x3f71 /* OF */ +#define CMD_HALT 0x7638 /* HL */ +#define CMD_SUSPEND 0x1b1b /* ZZ */ + +struct spi_slave_system_control_priv { + struct spi_device *spi; + struct completion finished; + struct spi_transfer xfer; + struct spi_message msg; + __le16 cmd; +}; + +static +int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv); + +static void spi_slave_system_control_complete(void *arg) +{ + struct spi_slave_system_control_priv *priv = arg; + u16 cmd; + int ret; + + if (priv->msg.status) + goto terminate; + + cmd = le16_to_cpu(priv->cmd); + switch (cmd) { + case CMD_REBOOT: + pr_info("Rebooting system...\n"); + kernel_restart(NULL); + + case CMD_POWEROFF: + pr_info("Powering off system...\n"); + kernel_power_off(); + break; + + case CMD_HALT: + pr_info("Halting system...\n"); + kernel_halt(); + break; + + case CMD_SUSPEND: + pr_info("Suspending system...\n"); + pm_suspend(PM_SUSPEND_MEM); + break; + + default: + pr_warn("%s: Unknown command 0x%x\n", __func__, cmd); + break; + } + + ret = spi_slave_system_control_submit(priv); + if (ret) + goto terminate; + + return; + +terminate: + pr_info("%s: Terminating\n", __func__); + complete(&priv->finished); +} + +static +int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv) +{ + int ret; + + spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1); + + priv->msg.complete = spi_slave_system_control_complete; + priv->msg.context = priv; + + ret = spi_async(priv->spi, &priv->msg); + if (ret) + pr_err("%s: spi_async() failed %d\n", __func__, ret); + + return ret; +} + +static int spi_slave_system_control_probe(struct spi_device *spi) +{ + struct spi_slave_system_control_priv *priv; + int ret; + + /* + * bits_per_word cannot be configured in platform data + */ + spi->bits_per_word = 8; + + ret = spi_setup(spi); + if (ret < 0) + return ret; + + priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->spi = spi; + init_completion(&priv->finished); + priv->xfer.rx_buf = &priv->cmd; + priv->xfer.len = sizeof(priv->cmd); + + ret = spi_slave_system_control_submit(priv); + if (ret) + return ret; + + spi_set_drvdata(spi, priv); + return 0; +} + +static int spi_slave_system_control_remove(struct spi_device *spi) +{ + struct spi_slave_system_control_priv *priv = spi_get_drvdata(spi); + + spi_slave_abort(spi); + wait_for_completion(&priv->finished); + return 0; +} + +static struct spi_driver spi_slave_system_control_driver = { + .driver = { + .name = "spi-slave-system-control", + }, + .probe = spi_slave_system_control_probe, + .remove = spi_slave_system_control_remove, +}; +module_spi_driver(spi_slave_system_control_driver); + +MODULE_AUTHOR("Geert Uytterhoeven <[email protected]>"); +MODULE_DESCRIPTION("SPI slave handler controlling system state"); +MODULE_LICENSE("GPL v2"); -- 1.9.1
