spi: slave: Add SPI slave handler controlling system state
Add an example SPI slave handler to allow remote control of system
reboot, power off, halt, and suspend.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/drivers/spi/spi-slave-system-control.c b/drivers/spi/spi-slave-system-control.c
new file mode 100644
index 0000000..c0257e9
--- /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) 2016-2017 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.
+ *
+ * Usage (assuming /dev/spidev2.0 corresponds to the SPI master on the remote
+ * system):
+ *
+ * # reboot='\x7c\x50'
+ * # poweroff='\x71\x3f'
+ * # halt='\x38\x76'
+ * # suspend='\x1b\x1b'
+ * # spidev_test -D /dev/spidev2.0 -p $suspend # or $reboot, $poweroff, $halt
+ */
+
+#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 0x7c50 /* rb */
+#define CMD_POWEROFF 0x713f /* OF */
+#define CMD_HALT 0x3876 /* 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;
+ __be16 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 = be16_to_cpu(priv->cmd);
+ switch (cmd) {
+ case CMD_REBOOT:
+ dev_info(&priv->spi->dev, "Rebooting system...\n");
+ kernel_restart(NULL);
+
+ case CMD_POWEROFF:
+ dev_info(&priv->spi->dev, "Powering off system...\n");
+ kernel_power_off();
+ break;
+
+ case CMD_HALT:
+ dev_info(&priv->spi->dev, "Halting system...\n");
+ kernel_halt();
+ break;
+
+ case CMD_SUSPEND:
+ dev_info(&priv->spi->dev, "Suspending system...\n");
+ pm_suspend(PM_SUSPEND_MEM);
+ break;
+
+ default:
+ dev_warn(&priv->spi->dev, "Unknown command 0x%x\n", cmd);
+ break;
+ }
+
+ ret = spi_slave_system_control_submit(priv);
+ if (ret)
+ goto terminate;
+
+ return;
+
+terminate:
+ dev_info(&priv->spi->dev, "Terminating\n");
+ 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)
+ dev_err(&priv->spi->dev, "spi_async() failed %d\n", ret);
+
+ return ret;
+}
+
+static int spi_slave_system_control_probe(struct spi_device *spi)
+{
+ struct spi_slave_system_control_priv *priv;
+ int 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 <geert+renesas@glider.be>");
+MODULE_DESCRIPTION("SPI slave handler controlling system state");
+MODULE_LICENSE("GPL v2");