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/*
* 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 void spi_slave_time_remove(struct spi_device *spi)
{
struct spi_slave_time_priv *priv = spi_get_drvdata(spi);
spi_target_abort(spi);
wait_for_completion(&priv->finished);
}
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");
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