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Date: Mon, 12 Sep 2016 22:50:45 +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>,
Hisashi Nakamura <hisashi.nakamura.ak@...esas.com>,
Hiromitsu Yamasaki <hiromitsu.yamasaki.ym@...esas.com>,
linux-spi@...r.kernel.org, devicetree@...r.kernel.org,
linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH/RFC v2 6/7] 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>
---
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 | 126 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 133 insertions(+)
create mode 100644 drivers/spi/spi-slave-time.c
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index fa13a3663de5bde0..515bddee4018c246 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -749,6 +749,12 @@ 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 96e5c0d6e5bc6151..ba4a7e79fe113d3e 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -100,3 +100,4 @@ 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..69e970ecb579adc7
--- /dev/null
+++ b/drivers/spi/spi-slave-time.c
@@ -0,0 +1,126 @@
+/*
+ * 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 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.
+ */
+
+#include <linux/completion.h>
+#include <linux/module.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:
+ pr_info("%s: Terminating\n", __func__);
+ complete(&priv->finished);
+}
+
+static int spi_slave_time_submit(struct spi_slave_time_priv *priv)
+{
+ u32 rem_ns;
+ int ret;
+ u64 ts;
+
+ ts = local_clock();
+ rem_ns = do_div(ts, 1000000000) / 1000;
+
+ priv->buf[0] = cpu_to_be32(ts);
+ priv->buf[1] = cpu_to_be32(rem_ns);
+
+ 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)
+ pr_err("%s: spi_async() failed %d\n", __func__, ret);
+
+ return ret;
+}
+
+static int spi_slave_time_probe(struct spi_device *spi)
+{
+ struct spi_slave_time_priv *priv;
+ int ret;
+
+ /*
+ * bits_per_word cannot be configured in platform data
+ */
+ spi->bits_per_word = 8;
+
+ ret = spi_setup(spi);
+ if (ret < 0)
+ return 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");
--
1.9.1
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