mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-27 14:43:58 +08:00
29f9ffa0e1
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+renesas@glider.be> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Signed-off-by: Mark Brown <broonie@kernel.org>
130 lines
2.9 KiB
C
130 lines
2.9 KiB
C
/*
|
|
* 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");
|