Add an example SPI slave handler responding with the uptime at the time
of reception of the last SPI message.
This can be used by an external microcontroller as a dead man's switch.
Signed-off-by: Geert Uytterhoeven <geert+rene...@glider.be>
---
v5:
- Add usage documentation to file header,
- Replace pr_*() by dev_*(), stop printing __func__,
- Rename rem_ns to rem_us, as the remainder is in microseconds,
- Remove spi_setup() call to configure 8 bits per word, as that's the
default,
v4:
- No changes,
v3:
- Add #include <linux/sched/clock.h>,
v2:
- Resolve semantic differences in patch description, file header, and
module description,
- 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().
---
drivers/spi/Kconfig | 6 ++
drivers/spi/Makefile | 1 +
drivers/spi/spi-slave-time.c | 129 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 136 insertions(+)
create mode 100644 drivers/spi/spi-slave-time.c
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index f21499b1f71ab7c3..9972ee2a8454a2fc 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -797,6 +797,12 @@ config SPI_SLAVE
if SPI_SLAVE
+config SPI_SLAVE_TIME
+ tristate "SPI slave handler reporting boot up time"
+ help
+ SPI slave handler responding with the time of reception of the last
+ SPI message.
+
endif # SPI_SLAVE
endif # SPI
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index e50852c6fcb87d8b..fb078693dbe40da4 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -107,3 +107,4 @@ obj-$(CONFIG_SPI_XTENSA_XTFPGA) +=
spi-xtensa-xtfpga.o
obj-$(CONFIG_SPI_ZYNQMP_GQSPI) += spi-zynqmp-gqspi.o
# SPI slave protocol handlers
+obj-$(CONFIG_SPI_SLAVE_TIME) += spi-slave-time.o
diff --git a/drivers/spi/spi-slave-time.c b/drivers/spi/spi-slave-time.c
new file mode 100644
index 0000000000000000..f2e07a392d6863ea
--- /dev/null
+++ b/drivers/spi/spi-slave-time.c
@@ -0,0 +1,129 @@
+/*
+ * SPI slave handler reporting uptime at reception of previous SPI message
+ *
+ * This SPI slave handler sends the time of reception of the last SPI message
+ * as two 32-bit unsigned integers in binary format and in network byte order,
+ * representing the number of seconds and fractional seconds (in microseconds)
+ * since boot up.
+ *
+ * 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):
+ *
+ * # spidev_test -D /dev/spidev2.0 -p dummy-8B
+ * spi mode: 0x0
+ * bits per word: 8
+ * max speed: 500000 Hz (500 KHz)
+ * RX | 00 00 04 6D 00 09 5B BB ...
+ * ^^^^^ ^^^^^^^^
+ * seconds microseconds
+ */
+
+#include <linux/completion.h>
+#include <linux/module.h>
+#include <linux/sched/clock.h>
+#include <linux/spi/spi.h>
+
+
+struct spi_slave_time_priv {
+ struct spi_device *spi;
+ struct completion finished;
+ struct spi_transfer xfer;
+ struct spi_message msg;
+ __be32 buf[2];
+};
+
+static int spi_slave_time_submit(struct spi_slave_time_priv *priv);
+
+static void spi_slave_time_complete(void *arg)
+{
+ struct spi_slave_time_priv *priv = arg;
+ int ret;
+
+ ret = priv->msg.status;
+ if (ret)
+ goto terminate;
+
+ ret = spi_slave_time_submit(priv);
+ if (ret)
+ goto terminate;
+
+ return;
+
+terminate:
+ dev_info(&priv->spi->dev, "Terminating\n");
+ complete(&priv->finished);
+}
+
+static int spi_slave_time_submit(struct spi_slave_time_priv *priv)
+{
+ u32 rem_us;
+ int ret;
+ u64 ts;
+
+ ts = local_clock();
+ rem_us = do_div(ts, 1000000000) / 1000;
+
+ priv->buf[0] = cpu_to_be32(ts);
+ priv->buf[1] = cpu_to_be32(rem_us);
+
+ spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1);
+
+ priv->msg.complete = spi_slave_time_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_time_probe(struct spi_device *spi)
+{
+ struct spi_slave_time_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.tx_buf = priv->buf;
+ priv->xfer.len = sizeof(priv->buf);
+
+ ret = spi_slave_time_submit(priv);
+ if (ret)
+ return ret;
+
+ spi_set_drvdata(spi, priv);
+ return 0;
+}
+
+static int spi_slave_time_remove(struct spi_device *spi)
+{
+ struct spi_slave_time_priv *priv = spi_get_drvdata(spi);
+
+ spi_slave_abort(spi);
+ wait_for_completion(&priv->finished);
+ return 0;
+}
+
+static struct spi_driver spi_slave_time_driver = {
+ .driver = {
+ .name = "spi-slave-time",
+ },
+ .probe = spi_slave_time_probe,
+ .remove = spi_slave_time_remove,
+};
+module_spi_driver(spi_slave_time_driver);
+
+MODULE_AUTHOR("Geert Uytterhoeven <geert+rene...@glider.be>");
+MODULE_DESCRIPTION("SPI slave reporting uptime at previous SPI message");
+MODULE_LICENSE("GPL v2");
--
2.7.4
