Commit 29f9ffa0 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Mark Brown
Browse files

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: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent aa2ea911

drivers/spi/Kconfig

+6 −0
Original line number Diff line number Diff line
@@ -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

drivers/spi/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

drivers/spi/spi-slave-time.c

0 → 100644
+129 −0
Original line number Diff line number Diff line 
/*

 * 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");