Add an SPI slave handler to allow remote control of system reboot, power off, halt, and suspend.
Signed-off-by: Geert Uytterhoeven <[email protected]> --- FIXME kthread_stop() hangs, as spi_write() is blocked on a completion --- drivers/spi/Kconfig | 6 ++ drivers/spi/Makefile | 1 + drivers/spi/spi-slave-system-control.c | 134 +++++++++++++++++++++++++++++++++ 3 files changed, 141 insertions(+) create mode 100644 drivers/spi/spi-slave-system-control.c diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig index e9b2f48574464949..9657415125ccb631 100644 --- a/drivers/spi/Kconfig +++ b/drivers/spi/Kconfig @@ -754,6 +754,12 @@ 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 dc67b8f137e2ced0..3b0487a9da91dfa8 100644 --- a/drivers/spi/Makefile +++ b/drivers/spi/Makefile @@ -100,3 +100,4 @@ 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..350711dec1281675 --- /dev/null +++ b/drivers/spi/spi-slave-system-control.c @@ -0,0 +1,134 @@ +/* + * 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/module.h> +#include <linux/reboot.h> +#include <linux/sched.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 task_struct *thread; +}; + +static int spi_slave_system_control_send(struct spi_device *spi) +{ + __le16 cmd; + int error; + + error = spi_read(spi, &cmd, sizeof(cmd)); + if (error) + return error; + + switch (le16_to_cpu(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; + } + return 0; +} + +static int spi_slave_system_control_thread(void *data) +{ + struct spi_slave_system_control_priv *priv = data; + int error; + + while (!kthread_should_stop()) { + error = spi_slave_system_control_send(priv->spi); + if (error) + pr_err("%s: SPI transfer failed %d\n", __func__, error); + } + + return 0; +} + +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; + priv->thread = kthread_run(spi_slave_system_control_thread, priv, + "spi-slave-system-control/%s", + dev_name(&spi->dev)); + if (IS_ERR(priv->thread)) + return PTR_ERR(priv->thread); + + 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); + + /* FIXME Doesn't work, as spi_read() is blocked on a completion */ + kthread_stop(priv->thread); + 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 reporting boot up time"); +MODULE_LICENSE("GPL v2"); -- 1.9.1
