spi: slave: Add SPI slave handler reporting uptime at previous message

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>
This commit is contained in:
Geert Uytterhoeven 2017-05-22 15:11:44 +02:00 committed by Mark Brown
parent aa2ea9115b
commit 29f9ffa0e1
3 changed files with 136 additions and 0 deletions

View File

@ -796,6 +796,12 @@ 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

View File

@ -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

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@ -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");