1 files changed, 129 insertions, 0 deletions
diff --git a/drivers/spi/spi-slave-time.c b/drivers/spi/spi-slave-time.c
new file mode 100644
index 000000000..f2e07a392
--- /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+renesas@glider.be>");
+MODULE_DESCRIPTION("SPI slave reporting uptime at previous SPI message");
+MODULE_LICENSE("GPL v2");