1 /* 2 * SPI slave handler reporting uptime at reception of previous SPI message 3 * 4 * This SPI slave handler sends the time of reception of the last SPI message 5 * 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 bvba 10 * 11 * This file is subject to the terms and conditions of the GNU General Public 12 * License. See the file "COPYING" in the main directory of this archive 13 * for more details. 14 * 15 * Usage (assuming /dev/spidev2.0 corresponds to the SPI master on the remote 16 * system): 17 * 18 * # spidev_test -D /dev/spidev2.0 -p dummy-8B 19 * spi mode: 0x0 20 * bits per word: 8 21 * max speed: 500000 Hz (500 KHz) 22 * RX | 00 00 04 6D 00 09 5B BB ... 23 * ^^^^^ ^^^^^^^^ 24 * seconds microseconds 25 */ 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 33 struct 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 41 static int spi_slave_time_submit(struct spi_slave_time_priv *priv); 42 43 static 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 58 terminate: 59 dev_info(&priv->spi->dev, "Terminating\n"); 60 complete(&priv->finished); 61 } 62 63 static 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 87 static 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 } 108 109 static int spi_slave_time_remove(struct spi_device *spi) 110 { 111 struct spi_slave_time_priv *priv = spi_get_drvdata(spi); 112 113 spi_slave_abort(spi); 114 wait_for_completion(&priv->finished); 115 return 0; 116 } 117 118 static struct spi_driver spi_slave_time_driver = { 119 .driver = { 120 .name = "spi-slave-time", 121 }, 122 .probe = spi_slave_time_probe, 123 .remove = spi_slave_time_remove, 124 }; 125 module_spi_driver(spi_slave_time_driver); 126 127 MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>"); 128 MODULE_DESCRIPTION("SPI slave reporting uptime at previous SPI message"); 129 MODULE_LICENSE("GPL v2"); 130