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Message-Id: <1495458705-11692-6-git-send-email-geert+renesas@glider.be>
Date: Mon, 22 May 2017 15:11:44 +0200
From: Geert Uytterhoeven <geert+renesas@...der.be>
To: Mark Brown <broonie@...nel.org>
Cc: Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Magnus Damm <magnus.damm@...il.com>,
Wolfram Sang <wsa+renesas@...g-engineering.com>,
Hiromitsu Yamasaki <hiromitsu.yamasaki.ym@...esas.com>,
Jiada Wang <jiada_wang@...tor.com>,
Matt Porter <mporter@...sulko.com>, linux-spi@...r.kernel.org,
devicetree@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v5 5/6] 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@...der.be>
---
v5:
- Add usage documentation to file header,
- Replace pr_*() by dev_*(), stop printing __func__,
- Rename rem_ns to rem_us, as the remainder is in microseconds,
- Remove spi_setup() call to configure 8 bits per word, as that's the
default,
v4:
- No changes,
v3:
- Add #include <linux/sched/clock.h>,
v2:
- Resolve semantic differences in patch description, file header, and
module description,
- Use spi_async() instead of spi_read(),
- Submit the next transfer from the previous transfer's completion
callback, removing the need for a thread,
- Let .remove() call spi_slave_abort() to cancel the current ongoing
transfer, and wait for the completion to terminate,
- Remove FIXME about hanging kthread_stop().
---
drivers/spi/Kconfig | 6 ++
drivers/spi/Makefile | 1 +
drivers/spi/spi-slave-time.c | 129 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 136 insertions(+)
create mode 100644 drivers/spi/spi-slave-time.c
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index f21499b1f71ab7c3..9972ee2a8454a2fc 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -797,6 +797,12 @@ 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
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index e50852c6fcb87d8b..fb078693dbe40da4 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -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
diff --git a/drivers/spi/spi-slave-time.c b/drivers/spi/spi-slave-time.c
new file mode 100644
index 0000000000000000..f2e07a392d6863ea
--- /dev/null
+++ b/drivers/spi/spi-slave-time.c
@@ -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@...der.be>");
+MODULE_DESCRIPTION("SPI slave reporting uptime at previous SPI message");
+MODULE_LICENSE("GPL v2");
--
2.7.4
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