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@xxxxxxxxx>
---
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 <geert+renesas@xxxxxxxxx>");
+MODULE_DESCRIPTION("SPI slave handler controlling system state");
+MODULE_LICENSE("GPL v2");
--
1.9.1
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