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/Kconfig b/drivers/spi/Kconfig
index ade542c5bfd87e37c196afe7142f9f1ae3305c48..e6d9e329a3801d6d59025610104866d811477b0e 100644 (file)
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -802,6 +802,12 @@ 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 fb078693dbe40da4e6e40e72487fa29ab2684cae..1d7923e8c63bc22b10cdca1a6104ea83a2e7c41c 100644 (file)
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -108,3 +108,4 @@ 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 (file)
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");