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1/*2 * SPI slave handler reporting uptime at reception of previous SPI message3 *4 * This SPI slave handler sends the time of reception of the last SPI message5 * as two 32-bit unsigned integers in binary format and in network byte order,6 * representing the number of seconds and fractional seconds (in microseconds)7 * since boot up.8 *9 * Copyright (C) 2016-2017 Glider bvba10 *11 * This file is subject to the terms and conditions of the GNU General Public12 * License. See the file "COPYING" in the main directory of this archive13 * for more details.14 *15 * Usage (assuming /dev/spidev2.0 corresponds to the SPI master on the remote16 * system):17 *18 * # spidev_test -D /dev/spidev2.0 -p dummy-8B19 * spi mode: 0x020 * bits per word: 821 * max speed: 500000 Hz (500 KHz)22 * RX | 00 00 04 6D 00 09 5B BB ...23 * ^^^^^ ^^^^^^^^24 * seconds microseconds25 */26 27#include <linux/completion.h>28#include <linux/module.h>29#include <linux/sched/clock.h>30#include <linux/spi/spi.h>31 32 33struct spi_slave_time_priv {34 struct spi_device *spi;35 struct completion finished;36 struct spi_transfer xfer;37 struct spi_message msg;38 __be32 buf[2];39};40 41static int spi_slave_time_submit(struct spi_slave_time_priv *priv);42 43static void spi_slave_time_complete(void *arg)44{45 struct spi_slave_time_priv *priv = arg;46 int ret;47 48 ret = priv->msg.status;49 if (ret)50 goto terminate;51 52 ret = spi_slave_time_submit(priv);53 if (ret)54 goto terminate;55 56 return;57 58terminate:59 dev_info(&priv->spi->dev, "Terminating\n");60 complete(&priv->finished);61}62 63static int spi_slave_time_submit(struct spi_slave_time_priv *priv)64{65 u32 rem_us;66 int ret;67 u64 ts;68 69 ts = local_clock();70 rem_us = do_div(ts, 1000000000) / 1000;71 72 priv->buf[0] = cpu_to_be32(ts);73 priv->buf[1] = cpu_to_be32(rem_us);74 75 spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1);76 77 priv->msg.complete = spi_slave_time_complete;78 priv->msg.context = priv;79 80 ret = spi_async(priv->spi, &priv->msg);81 if (ret)82 dev_err(&priv->spi->dev, "spi_async() failed %d\n", ret);83 84 return ret;85}86 87static int spi_slave_time_probe(struct spi_device *spi)88{89 struct spi_slave_time_priv *priv;90 int ret;91 92 priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);93 if (!priv)94 return -ENOMEM;95 96 priv->spi = spi;97 init_completion(&priv->finished);98 priv->xfer.tx_buf = priv->buf;99 priv->xfer.len = sizeof(priv->buf);100 101 ret = spi_slave_time_submit(priv);102 if (ret)103 return ret;104 105 spi_set_drvdata(spi, priv);106 return 0;107}108 109static void spi_slave_time_remove(struct spi_device *spi)110{111 struct spi_slave_time_priv *priv = spi_get_drvdata(spi);112 113 spi_target_abort(spi);114 wait_for_completion(&priv->finished);115}116 117static struct spi_driver spi_slave_time_driver = {118 .driver = {119 .name = "spi-slave-time",120 },121 .probe = spi_slave_time_probe,122 .remove = spi_slave_time_remove,123};124module_spi_driver(spi_slave_time_driver);125 126MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");127MODULE_DESCRIPTION("SPI slave reporting uptime at previous SPI message");128MODULE_LICENSE("GPL v2");129