Add an SPI slave handler to allow remote control of system reboot, power
off, halt, and suspend.
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
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 <geert+renesas@xxxxxxxxx>");
+MODULE_DESCRIPTION("SPI slave reporting boot up time");
+MODULE_LICENSE("GPL v2");
--
1.9.1
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