[PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Wolfram Sang]

This is a sloppy logic analyzer using GPIOs. It comes with a script to
isolate a CPU for polling. While this is definitely not a production
level analyzer, it can be a helpful first view when remote debugging.
Read the documentation for details.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 .../dev-tools/gpio-sloppy-logic-analyzer.rst  |  71 ++++
 Documentation/dev-tools/index.rst             |   1 +
 drivers/gpio/Kconfig                          |  17 +
 drivers/gpio/Makefile                         |   1 +
 drivers/gpio/gpio-sloppy-logic-analyzer.c     | 340 ++++++++++++++++++
 tools/gpio/gpio-sloppy-logic-analyzer         | 222 ++++++++++++
 6 files changed, 652 insertions(+)
 create mode 100644 Documentation/dev-tools/gpio-sloppy-logic-analyzer.rst
 create mode 100644 drivers/gpio/gpio-sloppy-logic-analyzer.c
 create mode 100755 tools/gpio/gpio-sloppy-logic-analyzer

diff --git a/Documentation/dev-tools/gpio-sloppy-logic-analyzer.rst b/Documentation/dev-tools/gpio-sloppy-logic-analyzer.rst
new file mode 100644
index 000000000000..c8ae20d5ff17
--- /dev/null
+++ b/Documentation/dev-tools/gpio-sloppy-logic-analyzer.rst
@@ -0,0 +1,71 @@
+=============================================
+Linux Kernel GPIO based sloppy logic analyzer
+=============================================
+
+:Author: Wolfram Sang
+
+Introduction
+============
+
+This document briefly describes how to run the GPIO based in-kernel sloppy
+logic analyzer running on an isolated CPU.
+
+Note that this is a last resort analyzer which can be affected by latencies,
+non-deterministic code paths and non-maskable interrupts. It is called 'sloppy'
+for a reason. However, for e.g. remote development, it may be useful to get a
+first view and aid further debugging.
+
+Setup
+=====
+
+Tell the kernel which GPIOs are used as probes. For a Device Tree based system,
+you need to use the following bindings. Because these bindings are only for
+debugging, there is no official schema::
+
+    i2c-analyzer {
+            compatible = "gpio-sloppy-logic-analyzer";
+            probe-gpios = <&gpio6 21 GPIO_OPEN_DRAIN>, <&gpio6 4 GPIO_OPEN_DRAIN>;
+            probe-names = "SCL", "SDA";
+    };
+
+Note that you must provide a name for every GPIO specified. Currently a
+maximum of 8 probes are supported. 32 are likely possible but are not
+implemented yet.
+
+Usage
+=====
+
+The logic analyzer is configurable via files in debugfs. However, it is
+strongly recommended to not use them directly, but to use the script
+``tools/gpio/gpio-sloppy-logic-analyzer``. Besides checking parameters more
+extensively, it will isolate the CPU core so you will have the least
+disturbance while measuring.
+
+The script has a help option explaining the parameters. For the above DT
+snippet which analyzes an I2C bus at 400kHz on a Renesas Salvator-XS board, the
+following settings are used: The isolated CPU shall be CPU1 because it is a big
+core in a big.LITTLE setup. Because CPU1 is the default, we don't need a
+parameter. The bus speed is 400kHz. So, the sampling theorem says we need to
+sample at least at 800kHz. However, falling edges of both signals in an I2C
+start condition happen faster, so we need a higher sampling frequency, e.g.
+``-s 1500000`` for 1.5MHz. Also, we don't want to sample right away but wait
+for a start condition on an idle bus. So, we need to set a trigger to a falling
+edge on SDA while SCL stays high, i.e. ``-t 1H+2F``. Last is the duration, let
+us assume 15ms here which results in the parameter ``-d 15000``. So,
+altogether::
+
+    gpio-sloppy-logic-analyzer -s 1500000 -t 1H+2F -d 15000
+
+Note that the process will return you back to the prompt but a sub-process is
+still sampling in the background. Unless this has finished, you will not find a
+result file in the current or specified directory. For the above example, we
+will then need to trigger I2C communication::
+
+    i2cdetect -y -r <your bus number>
+
+Result is a .sr file to be consumed with PulseView or sigrok-cli from the free
+`sigrok`_ project. It is a zip file which also contains the binary sample data
+which may be consumed by other software. The filename is the logic analyzer
+instance name plus a since-epoch timestamp.
+
+.. _sigrok: https://sigrok.org/
diff --git a/Documentation/dev-tools/index.rst b/Documentation/dev-tools/index.rst
index 010a2af1e7d9..cdf1356a9c94 100644
--- a/Documentation/dev-tools/index.rst
+++ b/Documentation/dev-tools/index.rst
@@ -32,6 +32,7 @@ Documentation/dev-tools/testing-overview.rst
    kgdb
    kselftest
    kunit/index
+   gpio-sloppy-logic-analyzer
 
 
 .. only::  subproject and html
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 60d9374c72c0..4c88bbd6262b 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1696,4 +1696,21 @@ config GPIO_VIRTIO
 
 endmenu
 
+menu "GPIO hardware hacking tools"
+
+config GPIO_SLOPPY_LOGIC_ANALYZER
+	tristate "Sloppy GPIO logic analyzer"
+	depends on (GPIOLIB || COMPILE_TEST) && EXPERT
+	help
+	  This option enables support for a sloppy logic analyzer using polled
+	  GPIOs. Use the 'tools/gpio/gpio-sloppy-logic-analyzer' script with
+	  this driver. The script will make it easier to use and will also
+	  isolate a CPU for the polling task. Note that this is a last resort
+	  analyzer which can be affected by latencies, non-deterministic code
+	  paths, or NMIs. However, for e.g. remote development, it may be useful
+	  to get a first view and aid further debugging.
+
+	  If this driver is built as a module it will be called
+	  'gpio-sloppy-logic-analyzer'.
+endmenu
 endif
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 71ee9fc2ff83..4880c131f783 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -74,6 +74,7 @@ obj-$(CONFIG_GPIO_IT87)			+= gpio-it87.o
 obj-$(CONFIG_GPIO_IXP4XX)		+= gpio-ixp4xx.o
 obj-$(CONFIG_GPIO_JANZ_TTL)		+= gpio-janz-ttl.o
 obj-$(CONFIG_GPIO_KEMPLD)		+= gpio-kempld.o
+obj-$(CONFIG_GPIO_SLOPPY_LOGIC_ANALYZER) += gpio-sloppy-logic-analyzer.o
 obj-$(CONFIG_GPIO_LOGICVC)		+= gpio-logicvc.o
 obj-$(CONFIG_GPIO_LOONGSON1)		+= gpio-loongson1.o
 obj-$(CONFIG_GPIO_LOONGSON)		+= gpio-loongson.o
diff --git a/drivers/gpio/gpio-sloppy-logic-analyzer.c b/drivers/gpio/gpio-sloppy-logic-analyzer.c
new file mode 100644
index 000000000000..24b72620429c
--- /dev/null
+++ b/drivers/gpio/gpio-sloppy-logic-analyzer.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Sloppy logic analyzer using GPIOs (to be run on an isolated CPU)
+ *
+ * Use the 'gpio-sloppy-logic-analyzer' script in the 'tools/gpio' folder for
+ * easier usage and further documentation. Note that this is a last resort
+ * analyzer which can be affected by latencies and non-deterministic code
+ * paths. However, for e.g. remote development, it may be useful to get a first
+ * view and aid further debugging.
+ *
+ * Copyright (C) Wolfram Sang <wsa@sang-engineering.com>
+ * Copyright (C) Renesas Electronics Corporation
+ */
+
+#include <linux/ctype.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/ktime.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+#include <linux/sizes.h>
+#include <linux/timekeeping.h>
+#include <linux/vmalloc.h>
+
+#define GPIO_LA_NAME "gpio-sloppy-logic-analyzer"
+#define GPIO_LA_DEFAULT_BUF_SIZE SZ_256K
+/* can be increased but then we need to extend the u8 buffers */
+#define GPIO_LA_MAX_PROBES 8
+#define GPIO_LA_NUM_TESTS 1024
+
+struct gpio_la_poll_priv {
+	struct mutex lock;
+	u32 buf_idx;
+	struct gpio_descs *descs;
+	unsigned long delay_ns;
+	unsigned long acq_delay;
+	struct debugfs_blob_wrapper blob;
+	struct dentry *debug_dir;
+	struct dentry *blob_dent;
+	struct debugfs_blob_wrapper meta;
+	struct device *dev;
+	unsigned int trig_len;
+	u8 *trig_data;
+};
+
+static struct dentry *gpio_la_poll_debug_dir;
+
+static __always_inline int gpio_la_get_array(struct gpio_descs *d, unsigned long *sptr)
+{
+	int ret;
+
+	ret = gpiod_get_array_value(d->ndescs, d->desc, d->info, sptr);
+	if (ret == 0 && fatal_signal_pending(current))
+		ret = -EINTR;
+
+	return ret;
+}
+
+static int fops_capture_set(void *data, u64 val)
+{
+	struct gpio_la_poll_priv *priv = data;
+	u8 *la_buf = priv->blob.data;
+	unsigned long state = 0; /* zeroed because GPIO arrays are bitfields */
+	unsigned long delay;
+	ktime_t start_time;
+	unsigned int i;
+	int ret;
+
+	if (!val)
+		return 0;
+
+	if (!la_buf)
+		return -ENOMEM;
+
+	if (!priv->delay_ns)
+		return -EINVAL;
+
+	mutex_lock(&priv->lock);
+	if (priv->blob_dent) {
+		debugfs_remove(priv->blob_dent);
+		priv->blob_dent = NULL;
+	}
+
+	priv->buf_idx = 0;
+
+	local_irq_disable();
+	preempt_disable_notrace();
+
+	/* Measure delay of reading GPIOs */
+	start_time = ktime_get();
+	for (i = 0; i < GPIO_LA_NUM_TESTS; i++) {
+		ret = gpio_la_get_array(priv->descs, &state);
+		if (ret)
+			goto gpio_err;
+	}
+
+	priv->acq_delay = ktime_sub(ktime_get(), start_time) / GPIO_LA_NUM_TESTS;
+	if (priv->delay_ns < priv->acq_delay) {
+		ret = -ERANGE;
+		goto gpio_err;
+	}
+
+	delay = priv->delay_ns - priv->acq_delay;
+
+	/* Wait for triggers */
+	for (i = 0; i < priv->trig_len; i+= 2) {
+		do {
+			ret = gpio_la_get_array(priv->descs, &state);
+			if (ret)
+				goto gpio_err;
+
+			ndelay(delay);
+		} while ((state & priv->trig_data[i]) != priv->trig_data[i + 1]);
+	}
+
+	/* With triggers, final state is also the first sample */
+	if (priv->trig_len)
+		la_buf[priv->buf_idx++] = state;
+
+	/* Sample */
+	while (priv->buf_idx < priv->blob.size) {
+		ret = gpio_la_get_array(priv->descs, &state);
+		if (ret)
+			goto gpio_err;
+
+		la_buf[priv->buf_idx++] = state;
+		ndelay(delay);
+	}
+gpio_err:
+	preempt_enable_notrace();
+	local_irq_enable();
+	if (ret)
+		dev_err(priv->dev, "couldn't read GPIOs: %d\n", ret);
+
+	kfree(priv->trig_data);
+	priv->trig_data = NULL;
+	priv->trig_len = 0;
+
+	priv->blob_dent = debugfs_create_blob("sample_data", 0400, priv->debug_dir, &priv->blob);
+	mutex_unlock(&priv->lock);
+
+	return ret;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_capture, NULL, fops_capture_set, "%llu\n");
+
+static int fops_buf_size_get(void *data, u64 *val)
+{
+	struct gpio_la_poll_priv *priv = data;
+
+	*val = priv->blob.size;
+
+	return 0;
+}
+
+static int fops_buf_size_set(void *data, u64 val)
+{
+	struct gpio_la_poll_priv *priv = data;
+	int ret = 0;
+	void *p;
+
+	if (!val)
+		return -EINVAL;
+
+	mutex_lock(&priv->lock);
+
+	vfree(priv->blob.data);
+	p = vzalloc(val);
+	if (!p) {
+		val = 0;
+		ret = -ENOMEM;
+	}
+
+	priv->blob.data = p;
+	priv->blob.size = val;
+
+	mutex_unlock(&priv->lock);
+	return ret;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_buf_size, fops_buf_size_get, fops_buf_size_set, "%llu\n");
+
+static int trigger_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, NULL, inode->i_private);
+}
+
+static ssize_t trigger_write(struct file *file, const char __user *ubuf,
+			     size_t count, loff_t *offset)
+{
+	struct seq_file *m = file->private_data;
+	struct gpio_la_poll_priv *priv = m->private;
+	char *buf;
+
+	/* upper limit is arbitrary but should be less than PAGE_SIZE */
+	if (count > 2048 || count & 1)
+		return -EINVAL;
+
+	buf = memdup_user(ubuf, count);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	priv->trig_data = buf;
+	priv->trig_len = count;
+
+	return count;
+}
+
+static const struct file_operations fops_trigger = {
+	.owner = THIS_MODULE,
+	.open = trigger_open,
+	.write = trigger_write,
+	.llseek = no_llseek,
+	.release = single_release,
+};
+
+static int gpio_la_poll_probe(struct platform_device *pdev)
+{
+	struct gpio_la_poll_priv *priv;
+	struct device *dev = &pdev->dev;
+	const char *devname = dev_name(dev);
+	const char *gpio_names[GPIO_LA_MAX_PROBES];
+	char *meta = NULL;
+	unsigned int i, meta_len = 0;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	mutex_init(&priv->lock);
+
+	fops_buf_size_set(priv, GPIO_LA_DEFAULT_BUF_SIZE);
+
+	priv->descs = devm_gpiod_get_array(dev, "probe", GPIOD_IN);
+	if (IS_ERR(priv->descs))
+		return PTR_ERR(priv->descs);
+
+	/* artificial limit to keep 1 byte per sample for now */
+	if (priv->descs->ndescs > GPIO_LA_MAX_PROBES)
+		return -EFBIG;
+
+	ret = device_property_read_string_array(dev, "probe-names", gpio_names,
+						priv->descs->ndescs);
+	if (ret >= 0 && ret != priv->descs->ndescs)
+		ret = -ENODATA;
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "error naming the GPIOs");
+
+	for (i = 0; i < priv->descs->ndescs; i++) {
+		unsigned int add_len;
+		char *new_meta, *consumer_name;
+
+		if (gpiod_cansleep(priv->descs->desc[i]))
+			return -EREMOTE;
+
+		consumer_name = kasprintf(GFP_KERNEL, "%s: %s", devname, gpio_names[i]);
+		if (!consumer_name)
+			return -ENOMEM;
+		gpiod_set_consumer_name(priv->descs->desc[i], consumer_name);
+		kfree(consumer_name);
+
+		/* '10' is length of 'probe00=\n\0' */
+		add_len = strlen(gpio_names[i]) + 10;
+
+		new_meta = devm_krealloc(dev, meta, meta_len + add_len, GFP_KERNEL);
+		if (!new_meta)
+			return -ENOMEM;
+
+		meta = new_meta;
+		meta_len += snprintf(meta + meta_len, add_len, "probe%02u=%s\n",
+				     i + 1, gpio_names[i]);
+	}
+
+	platform_set_drvdata(pdev, priv);
+	priv->dev = dev;
+
+	priv->meta.data = meta;
+	priv->meta.size = meta_len;
+	priv->debug_dir = debugfs_create_dir(devname, gpio_la_poll_debug_dir);
+	debugfs_create_blob("meta_data", 0400, priv->debug_dir, &priv->meta);
+	debugfs_create_ulong("delay_ns", 0600, priv->debug_dir, &priv->delay_ns);
+	debugfs_create_ulong("delay_ns_acquisition", 0400, priv->debug_dir, &priv->acq_delay);
+	debugfs_create_file_unsafe("buf_size", 0600, priv->debug_dir, priv, &fops_buf_size);
+	debugfs_create_file_unsafe("capture", 0200, priv->debug_dir, priv, &fops_capture);
+	debugfs_create_file_unsafe("trigger", 0200, priv->debug_dir, priv, &fops_trigger);
+
+	dev_info(dev, "initialized");
+	return 0;
+}
+
+static int gpio_la_poll_remove(struct platform_device *pdev)
+{
+	struct gpio_la_poll_priv *priv = platform_get_drvdata(pdev);
+
+	mutex_lock(&priv->lock);
+	debugfs_remove_recursive(priv->debug_dir);
+	mutex_unlock(&priv->lock);
+	mutex_destroy(&priv->lock);
+
+	return 0;
+}
+
+static const struct of_device_id gpio_la_poll_of_match[] = {
+	{ .compatible = GPIO_LA_NAME, },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, gpio_la_poll_of_match);
+
+static struct platform_driver gpio_la_poll_device_driver = {
+	.probe = gpio_la_poll_probe,
+	.remove = gpio_la_poll_remove,
+	.driver = {
+		.name = GPIO_LA_NAME,
+		.of_match_table = gpio_la_poll_of_match,
+	}
+};
+
+static int __init gpio_la_poll_init(void)
+{
+	gpio_la_poll_debug_dir = debugfs_create_dir(GPIO_LA_NAME, NULL);
+
+	return platform_driver_register(&gpio_la_poll_device_driver);
+}
+late_initcall(gpio_la_poll_init);
+
+static void __exit gpio_la_poll_exit(void)
+{
+	platform_driver_unregister(&gpio_la_poll_device_driver);
+	debugfs_remove_recursive(gpio_la_poll_debug_dir);
+}
+module_exit(gpio_la_poll_exit);
+
+MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
+MODULE_DESCRIPTION("Sloppy logic analyzer using GPIOs");
+MODULE_LICENSE("GPL v2");
diff --git a/tools/gpio/gpio-sloppy-logic-analyzer b/tools/gpio/gpio-sloppy-logic-analyzer
new file mode 100755
index 000000000000..23e2def39c75
--- /dev/null
+++ b/tools/gpio/gpio-sloppy-logic-analyzer
@@ -0,0 +1,222 @@
+#!/bin/sh -eu
+# Helper script for the Linux Kernel GPIO sloppy logic analyzer
+#
+# Copyright (C) Wolfram Sang <wsa@sang-engineering.com>
+# Copyright (C) Renesas Electronics Corporation
+#
+# TODO: support SI units in command line parameters?
+
+samplefreq=1000000
+numsamples=250000
+cpusetdir='/dev/cpuset'
+debugdir='/sys/kernel/debug'
+ladirname='gpio-sloppy-logic-analyzer'
+outputdir="$PWD"
+neededcmds='taskset zip'
+max_chans=8
+duration=
+initcpu=
+lainstance=
+lasysfsdir=
+triggerdat=
+trigger_bindat=
+progname="${0##*/}"
+print_help()
+{
+	cat <<EOF
+$progname - helper script for the Linux Kernel Sloppy GPIO Logic Analyzer
+Available options:
+	-c|--cpu <n>: which CPU to isolate for sampling. Only needed once. Default <1>.
+		      Remember that a more powerful CPU gives you higher sampling speeds.
+		      Also CPU0 is not recommended as it usually does extra bookkeeping.
+	-d|--duration-us <n>: number of microseconds to sample. Overrides -n, no default value.
+	-h|--help: print this help
+	-i|--instance <str>: name of the logic analyzer in case you have multiple instances. Default
+			     to first instance found
+	-k|--kernel-debug-dir: path to the kernel debugfs mountpoint. Default: <$debugdir>
+	-n|--num_samples <n>: number of samples to acquire. Default <$numsamples>
+	-o|--output-dir <str>: directory to put the result files. Default: current dir
+	-s|--sample_freq <n>: desired sampling frequency. Might be capped if too large. Default: 1MHz.
+	-t|--trigger <str>: pattern to use as trigger. <str> consists of two-char pairs. First
+			    char is channel number starting at "1". Second char is trigger level:
+			    "L" - low; "H" - high; "R" - rising; "F" - falling
+			    These pairs can be combined with "+", so "1H+2F" triggers when probe 1
+			    is high while probe 2 has a falling edge. You can have multiple triggers
+			    combined with ",". So, "1H+2F,1H+2R" is like the example before but it
+			    waits for a rising edge on probe 2 while probe 1 is still high after the
+			    first trigger has been met.
+			    Trigger data will only be used for the next capture and then be erased.
+Examples:
+Samples $numsamples values at 1MHz with an already prepared CPU or automatically prepares CPU1 if needed,
+use the first logic analyzer instance found:
+	'$progname'
+Samples 50us at 2MHz waiting for a falling edge on channel 2. CPU and instance as above:
+	'$progname -d 50 -s 2000000 -t "2F"'
+
+Note that the process exits after checking all parameters but a sub-process still works in
+the background. The result is only available once the sub-process finishes.
+
+Result is a .sr file to be consumed with PulseView from the free Sigrok project. It is
+a zip file which also contains the binary sample data which may be consumed by others.
+The filename is the logic analyzer instance name plus a since-epoch timestamp.
+EOF
+}
+
+fail()
+{
+	echo "$1"
+	exit 1
+}
+
+set_newmask()
+{
+	for f in $(find "$1" -iname "$2"); do echo "$newmask" > "$f" 2>/dev/null || true; done
+}
+
+init_cpu()
+{
+	isol_cpu="$1"
+	[ -d $cpusetdir ] || mkdir $cpusetdir
+	mount | grep -q $cpusetdir || mount -t cpuset cpuset $cpusetdir
+	[ -d "$lacpusetdir" ] || mkdir "$lacpusetdir"
+
+	cur_cpu="$(cat "$lacpusetdir"/cpus)"
+	[ "$cur_cpu" = "$isol_cpu" ] && return
+	[ -z "$cur_cpu" ] || fail "CPU$isol_cpu requested but CPU$cur_cpu already isolated"
+
+	echo "$isol_cpu" > "$lacpusetdir"/cpus || fail "Could not isolate CPU$isol_cpu. Does it exist?"
+	echo 1 > "$lacpusetdir"/cpu_exclusive
+	echo 0 > "$lacpusetdir"/mems
+
+	oldmask=$(cat /proc/irq/default_smp_affinity)
+	val=$((0x$oldmask & ~(1 << isol_cpu)))
+	newmask=$(printf "%x" $val)
+
+	set_newmask '/proc/irq' '*smp_affinity'
+	set_newmask '/sys/devices/virtual/workqueue/' 'cpumask'
+
+	# Move tasks away from isolated CPU
+	for p in $(ps -o pid | tail -n +2); do
+		mask=$(taskset -p "$p") || continue
+		# Ignore tasks with a custom mask, i.e. not equal $oldmask
+		[ "${mask##*: }" = "$oldmask" ] || continue
+		taskset -p "$newmask" "$p" || continue
+	done 2>/dev/null >/dev/null
+
+	echo 1 > /sys/module/rcupdate/parameters/rcu_cpu_stall_suppress
+
+	cpufreqgov="/sys/devices/system/cpu/cpu$isol_cpu/cpufreq/scaling_governor"
+	[ -w "$cpufreqgov" ] && echo 'performance' > "$cpufreqgov" || true
+}
+
+parse_triggerdat()
+{
+	oldifs="$IFS"
+	IFS=','; for trig in $1; do
+		mask=0; val1=0; val2=0
+		IFS='+'; for elem in $trig; do
+			chan=${elem%[lhfrLHFR]}
+			mode=${elem#$chan}
+			# Check if we could parse something and the channel number fits
+			[ "$chan" != "$elem" ] && [ "$chan" -le $max_chans ] || fail "Trigger syntax error: $elem"
+			bit=$((1 << (chan - 1)))
+			mask=$((mask | bit))
+			case $mode in
+				[hH]) val1=$((val1 | bit)); val2=$((val2 | bit));;
+				[fF]) val1=$((val1 | bit));;
+				[rR]) val2=$((val2 | bit));;
+			esac
+		done
+		trigger_bindat="$trigger_bindat$(printf '\\%o\\%o' $mask $val1)"
+		[ $val1 -ne $val2 ] && trigger_bindat="$trigger_bindat$(printf '\\%o\\%o' $mask $val2)"
+	done
+	IFS="$oldifs"
+}
+
+do_capture()
+{
+	taskset "$1" echo 1 > "$lasysfsdir"/capture || fail "Capture error! Check kernel log"
+
+	srtmp=$(mktemp -d)
+	echo 1 > "$srtmp"/version
+	cp "$lasysfsdir"/sample_data "$srtmp"/logic-1-1
+	cat > "$srtmp"/metadata <<EOF
+[global]
+sigrok version=0.2.0
+
+[device 1]
+capturefile=logic-1
+total probes=$(wc -l < "$lasysfsdir"/meta_data)
+samplerate=${samplefreq}Hz
+unitsize=1
+EOF
+	cat "$lasysfsdir"/meta_data >> "$srtmp"/metadata
+
+	zipname="$outputdir/${lasysfsdir##*/}-$(date +%s).sr"
+	zip -jq "$zipname" "$srtmp"/*
+	rm -rf "$srtmp"
+	delay_ack=$(cat "$lasysfsdir"/delay_ns_acquisition)
+	[ "$delay_ack" -eq 0 ] && delay_ack=1
+	echo "Logic analyzer done. Saved '$zipname'"
+	echo "Max sample frequency this time: $((1000000000 / delay_ack))Hz."
+}
+
+rep=$(getopt -a -l cpu:,duration-us:,help,instance:,kernel-debug-dir:,num_samples:,output-dir:,sample_freq:,trigger: -o c:d:hi:k:n:o:s:t: -- "$@") || exit 1
+eval set -- "$rep"
+while true; do
+	case "$1" in
+	-c|--cpu) initcpu="$2"; shift;;
+	-d|--duration-us) duration="$2"; shift;;
+	-h|--help) print_help; exit 0;;
+	-i|--instance) lainstance="$2"; shift;;
+	-k|--kernel-debug-dir) debugdir="$2"; shift;;
+	-n|--num_samples) numsamples="$2"; shift;;
+	-o|--output-dir) outputdir="$2"; shift;;
+	-s|--sample_freq) samplefreq="$2"; shift;;
+	-t|--trigger) triggerdat="$2"; shift;;
+	--) break;;
+	*) fail "error parsing command line: $*";;
+	esac
+	shift
+done
+
+for f in $neededcmds; do
+	command -v "$f" >/dev/null || fail "Command '$f' not found"
+done
+
+lacpusetdir="$cpusetdir/$ladirname"
+sysfsdir="$debugdir/$ladirname"
+
+[ "$samplefreq" -ne 0 ] || fail "Invalid sample frequency"
+
+[ -d "$sysfsdir" ] || fail "Could not find logic analyzer root dir '$sysfsdir'. Module loaded?"
+[ -x "$sysfsdir" ] || fail "Could not access logic analyzer root dir '$sysfsdir'. Need root?"
+
+if [ -n "$lainstance" ]; then
+	lasysfsdir="$sysfsdir/$lainstance"
+else
+	lasysfsdir="$(find "$sysfsdir" -mindepth 1 -type d -print -quit)"
+fi
+[ -d "$lasysfsdir" ] || fail "Logic analyzer directory '$lasysfsdir' not found!"
+[ -d "$outputdir" ] || fail "Output directory '$outputdir' not found!"
+
+[ -n "$initcpu" ] && init_cpu "$initcpu"
+[ -d "$lacpusetdir" ] || { echo "Auto-Isolating CPU1"; init_cpu 1; }
+
+ndelay=$((1000000000 / samplefreq))
+echo "$ndelay" > "$lasysfsdir"/delay_ns
+
+[ -n "$duration" ] && numsamples=$((samplefreq * duration / 1000000))
+echo $numsamples > "$lasysfsdir"/buf_size
+
+if [ -n "$triggerdat" ]; then
+	parse_triggerdat "$triggerdat"
+	printf "$trigger_bindat" > "$lasysfsdir"/trigger 2>/dev/null || fail "Trigger data '$triggerdat' rejected"
+fi
+
+workcpu=$(cat "$lacpusetdir"/effective_cpus)
+[ -n "$workcpu" ] || fail "No isolated CPU found"
+cpumask=$(printf '%x' $((1 << workcpu)))
+instance=${lasysfsdir##*/}
+echo "Setting up '$instance': $numsamples samples at ${samplefreq}Hz with ${triggerdat:-no} trigger using CPU$workcpu"
+do_capture "$cpumask" &
-- 
2.30.2

Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Andy Shevchenko]

On Tue, Nov 23, 2021 at 05:49:02PM +0100, Wolfram Sang wrote:
> This is a sloppy logic analyzer using GPIOs. It comes with a script to
> isolate a CPU for polling. While this is definitely not a production
> level analyzer, it can be a helpful first view when remote debugging.
> Read the documentation for details.

...

> +Result is a .sr file to be consumed with PulseView or sigrok-cli from the free
> +`sigrok`_ project. It is a zip file which also contains the binary sample data
> +which may be consumed by other software. The filename is the logic analyzer
> +instance name plus a since-epoch timestamp.
> +
> +.. _sigrok: https://sigrok.org/

Alas, yet another tool required... (Sad thoughts since recently has installed
PicoScope software).

...

>     kgdb
>     kselftest
>     kunit/index

> +   gpio-sloppy-logic-analyzer

Above looks like ordered, do we need some groups here or so?

...

> +	mutex_lock(&priv->lock);

> +	if (priv->blob_dent) {

Redundant (i.e. duplicate).

> +		debugfs_remove(priv->blob_dent);
> +		priv->blob_dent = NULL;
> +	}

...

> +gpio_err:

A bit confusing name. What about

enable_irq_and_free_data:

?

> +	preempt_enable_notrace();
> +	local_irq_enable();
> +	if (ret)
> +		dev_err(priv->dev, "couldn't read GPIOs: %d\n", ret);
> +
> +	kfree(priv->trig_data);
> +	priv->trig_data = NULL;
> +	priv->trig_len = 0;

...

> +static int gpio_la_poll_probe(struct platform_device *pdev)
> +{
> +	struct gpio_la_poll_priv *priv;
> +	struct device *dev = &pdev->dev;
> +	const char *devname = dev_name(dev);
> +	const char *gpio_names[GPIO_LA_MAX_PROBES];

> +	char *meta = NULL;
> +	unsigned int i, meta_len = 0;
> +	int ret;

Perhaps

	unsigned int i, meta_len = 0;
	char *meta = NULL;
	int ret;


...

> +	ret = device_property_read_string_array(dev, "probe-names", gpio_names,
> +						priv->descs->ndescs);
> +	if (ret >= 0 && ret != priv->descs->ndescs)

> +		ret = -ENODATA;

Don't remember if we already discussed this error code, but data is there,
it's not correct. EBADSLT? EBADR? ECHRNG?

> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "error naming the GPIOs");

...

> +	for (i = 0; i < priv->descs->ndescs; i++) {
> +		unsigned int add_len;
> +		char *new_meta, *consumer_name;
> +
> +		if (gpiod_cansleep(priv->descs->desc[i]))
> +			return -EREMOTE;
> +
> +		consumer_name = kasprintf(GFP_KERNEL, "%s: %s", devname, gpio_names[i]);
> +		if (!consumer_name)
> +			return -ENOMEM;
> +		gpiod_set_consumer_name(priv->descs->desc[i], consumer_name);
> +		kfree(consumer_name);
> +
> +		/* '10' is length of 'probe00=\n\0' */
> +		add_len = strlen(gpio_names[i]) + 10;
> +
> +		new_meta = devm_krealloc(dev, meta, meta_len + add_len, GFP_KERNEL);
> +		if (!new_meta)
> +			return -ENOMEM;
> +
> +		meta = new_meta;
> +		meta_len += snprintf(meta + meta_len, add_len, "probe%02u=%s\n",
> +				     i + 1, gpio_names[i]);

Do we really need the 'probe%02u=' part? It's redundant since it may be derived
from the line number of the output (and it always in [1..ndescs+1]).

> +	}

...

> +	dev_info(dev, "initialized");

Is it useful?

...

> +print_help()
> +{
> +	cat <<EOF

	cat << EOF

is slightly easier to read.

> +EOF
> +}

...

> +set_newmask()
> +{
> +	for f in $(find "$1" -iname "$2"); do echo "$newmask" > "$f" 2>/dev/null || true; done

While here it's okay, the rule of thumb is never use `for` or `while` against
the list of filenames.

> +}

...

> +init_cpu()
> +{
> +	isol_cpu="$1"

> +	[ -d $cpusetdir ] || mkdir $cpusetdir

`mkdir -p` and drop needless test.

> +	mount | grep -q $cpusetdir || mount -t cpuset cpuset $cpusetdir

> +	[ -d "$lacpusetdir" ] || mkdir "$lacpusetdir"

`mkdir -p` and drop needless test.

> +	cur_cpu="$(cat "$lacpusetdir"/cpus)"
> +	[ "$cur_cpu" = "$isol_cpu" ] && return
> +	[ -z "$cur_cpu" ] || fail "CPU$isol_cpu requested but CPU$cur_cpu already isolated"
> +
> +	echo "$isol_cpu" > "$lacpusetdir"/cpus || fail "Could not isolate CPU$isol_cpu. Does it exist?"
> +	echo 1 > "$lacpusetdir"/cpu_exclusive
> +	echo 0 > "$lacpusetdir"/mems
> +
> +	oldmask=$(cat /proc/irq/default_smp_affinity)

> +	val=$((0x$oldmask & ~(1 << isol_cpu)))
> +	newmask=$(printf "%x" $val)

Can be on one line (in a single expression).

> +	set_newmask '/proc/irq' '*smp_affinity'
> +	set_newmask '/sys/devices/virtual/workqueue/' 'cpumask'
> +
> +	# Move tasks away from isolated CPU
> +	for p in $(ps -o pid | tail -n +2); do
> +		mask=$(taskset -p "$p") || continue
> +		# Ignore tasks with a custom mask, i.e. not equal $oldmask
> +		[ "${mask##*: }" = "$oldmask" ] || continue
> +		taskset -p "$newmask" "$p" || continue
> +	done 2>/dev/null >/dev/null

`> /dev/null 2>&1` is idiomatic. And I think there is actually a subtle
difference between two.

> +	echo 1 > /sys/module/rcupdate/parameters/rcu_cpu_stall_suppress
> +
> +	cpufreqgov="/sys/devices/system/cpu/cpu$isol_cpu/cpufreq/scaling_governor"
> +	[ -w "$cpufreqgov" ] && echo 'performance' > "$cpufreqgov" || true
> +}

...

> +parse_triggerdat()
> +{
> +	oldifs="$IFS"
> +	IFS=','; for trig in $1; do
> +		mask=0; val1=0; val2=0
> +		IFS='+'; for elem in $trig; do
> +			chan=${elem%[lhfrLHFR]}
> +			mode=${elem#$chan}
> +			# Check if we could parse something and the channel number fits

> +			[ "$chan" != "$elem" ] && [ "$chan" -le $max_chans ] || fail "Trigger syntax error: $elem"

No need to execute `test` twice:

			[ "$chan" != "$elem" -a "$chan" -le $max_chans ] || fail "Trigger syntax error: $elem"

> +			bit=$((1 << (chan - 1)))
> +			mask=$((mask | bit))
> +			case $mode in
> +				[hH]) val1=$((val1 | bit)); val2=$((val2 | bit));;
> +				[fF]) val1=$((val1 | bit));;
> +				[rR]) val2=$((val2 | bit));;
> +			esac
> +		done

> +		trigger_bindat="$trigger_bindat$(printf '\\%o\\%o' $mask $val1)"
> +		[ $val1 -ne $val2 ] && trigger_bindat="$trigger_bindat$(printf '\\%o\\%o' $mask $val2)"

`printf` with arguments may be split to a separate helper function.

> +	done
> +	IFS="$oldifs"
> +}
> +
> +do_capture()
> +{
> +	taskset "$1" echo 1 > "$lasysfsdir"/capture || fail "Capture error! Check kernel log"

Shouldn't this function setup signal TRAPs?

> +	srtmp=$(mktemp -d)
> +	echo 1 > "$srtmp"/version
> +	cp "$lasysfsdir"/sample_data "$srtmp"/logic-1-1
> +	cat > "$srtmp"/metadata <<EOF

	cat > "$srtmp"/metadata << EOF

> +[global]
> +sigrok version=0.2.0
> +
> +[device 1]
> +capturefile=logic-1
> +total probes=$(wc -l < "$lasysfsdir"/meta_data)
> +samplerate=${samplefreq}Hz
> +unitsize=1
> +EOF
> +	cat "$lasysfsdir"/meta_data >> "$srtmp"/metadata
> +
> +	zipname="$outputdir/${lasysfsdir##*/}-$(date +%s).sr"
> +	zip -jq "$zipname" "$srtmp"/*
> +	rm -rf "$srtmp"
> +	delay_ack=$(cat "$lasysfsdir"/delay_ns_acquisition)
> +	[ "$delay_ack" -eq 0 ] && delay_ack=1
> +	echo "Logic analyzer done. Saved '$zipname'"
> +	echo "Max sample frequency this time: $((1000000000 / delay_ack))Hz."
> +}
> +
> +rep=$(getopt -a -l cpu:,duration-us:,help,instance:,kernel-debug-dir:,num_samples:,output-dir:,sample_freq:,trigger: -o c:d:hi:k:n:o:s:t: -- "$@") || exit 1
> +eval set -- "$rep"
> +while true; do
> +	case "$1" in
> +	-c|--cpu) initcpu="$2"; shift;;
> +	-d|--duration-us) duration="$2"; shift;;
> +	-h|--help) print_help; exit 0;;
> +	-i|--instance) lainstance="$2"; shift;;
> +	-k|--kernel-debug-dir) debugdir="$2"; shift;;
> +	-n|--num_samples) numsamples="$2"; shift;;
> +	-o|--output-dir) outputdir="$2"; shift;;
> +	-s|--sample_freq) samplefreq="$2"; shift;;
> +	-t|--trigger) triggerdat="$2"; shift;;
> +	--) break;;

> +	*) fail "error parsing command line: $*";;

$@ is better, actually one should never use $*.

> +	esac
> +	shift
> +done

...

Wondering, shouldn't be a simple validator before start that we have commands
present, such as zip?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Andy Shevchenko]

On Tue, Nov 23, 2021 at 08:45:55PM +0200, Andy Shevchenko wrote:
> On Tue, Nov 23, 2021 at 05:49:02PM +0100, Wolfram Sang wrote:

> > +			# Check if we could parse something and the channel number fits
> 
> > +			[ "$chan" != "$elem" ] && [ "$chan" -le $max_chans ] || fail "Trigger syntax error: $elem"
> 
> No need to execute `test` twice:
> 
> 			[ "$chan" != "$elem" -a "$chan" -le $max_chans ] || fail "Trigger syntax error: $elem"

On the second thought this might be a different logic...

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 4192 bytes --]

Hi Andy,

> > +Result is a .sr file to be consumed with PulseView or sigrok-cli from the free
> > +`sigrok`_ project. It is a zip file which also contains the binary sample data
> > +which may be consumed by other software. The filename is the logic analyzer
> > +instance name plus a since-epoch timestamp.
> > +
> > +.. _sigrok: https://sigrok.org/
> 
> Alas, yet another tool required... (Sad thoughts since recently has installed
> PicoScope software).

? For sure, another tool is required. Do you want the analyzer itself to
output pretty SVG files? :)

> 
> >     kgdb
> >     kselftest
> >     kunit/index
> 
> > +   gpio-sloppy-logic-analyzer
> 
> Above looks like ordered, do we need some groups here or so?

No feedback from the doc-maintainers so far. Can easily be fixed
afterwards if needed.

> > +	mutex_lock(&priv->lock);
> 
> > +	if (priv->blob_dent) {
> 
> Redundant (i.e. duplicate).

Nope, it can be NULL if allocating memory all goes wrong.

> > +gpio_err:
> 
> A bit confusing name. What about
> 
> enable_irq_and_free_data:

Yes, fixed in v6.

> > +	char *meta = NULL;
> > +	unsigned int i, meta_len = 0;
> > +	int ret;
> 
> Perhaps
> 
> 	unsigned int i, meta_len = 0;
> 	char *meta = NULL;
> 	int ret;

I'd like to keep the pointers grouped together.

> > +	if (ret >= 0 && ret != priv->descs->ndescs)
> 
> > +		ret = -ENODATA;
> 
> Don't remember if we already discussed this error code, but data is there,
> it's not correct. EBADSLT? EBADR? ECHRNG?

In your V1 review, you suggested -ENODATA. I will pick yet another one,
but it really matters zero in practice.

> > +		meta_len += snprintf(meta + meta_len, add_len, "probe%02u=%s\n",
> > +				     i + 1, gpio_names[i]);
> 
> Do we really need the 'probe%02u=' part? It's redundant since it may be derived
> from the line number of the output (and it always in [1..ndescs+1]).

It makes creating the .sr-file a lot easier. If you feel strong about
it, then you can later remove it and also update the script, I'd say.

> > +	dev_info(dev, "initialized");
> 
> Is it useful?

For the third time, yes!

> > +	cat <<EOF
> 
> 	cat << EOF
> 
> is slightly easier to read.

I'll fix it.

> > +	[ -d $cpusetdir ] || mkdir $cpusetdir
> 
> `mkdir -p` and drop needless test.

It is not the same. I prefer to bail out if e.g. '/dev/' does not exist
rather than silently create it.

> > +	val=$((0x$oldmask & ~(1 << isol_cpu)))
> > +	newmask=$(printf "%x" $val)
> 
> Can be on one line (in a single expression).

Ok.

> `> /dev/null 2>&1` is idiomatic. And I think there is actually a subtle
> difference between two.

What is the difference? Does it matter here?

> > +			[ "$chan" != "$elem" ] && [ "$chan" -le $max_chans ] || fail "Trigger syntax error: $elem"
> 
> No need to execute `test` twice:
> 
> 			[ "$chan" != "$elem" -a "$chan" -le $max_chans ] || fail "Trigger syntax error: $elem"

I read that '-a' and '-o' are deprecated. Dunno where but looking again
I found this: https://stackoverflow.com/questions/20449680/boolean-operators-a-o-in-bash

> 
> > +			bit=$((1 << (chan - 1)))
> > +			mask=$((mask | bit))
> > +			case $mode in
> > +				[hH]) val1=$((val1 | bit)); val2=$((val2 | bit));;
> > +				[fF]) val1=$((val1 | bit));;
> > +				[rR]) val2=$((val2 | bit));;
> > +			esac
> > +		done
> 
> > +		trigger_bindat="$trigger_bindat$(printf '\\%o\\%o' $mask $val1)"
> > +		[ $val1 -ne $val2 ] && trigger_bindat="$trigger_bindat$(printf '\\%o\\%o' $mask $val2)"
> 
> `printf` with arguments may be split to a separate helper function.

I think this is a micro-optimization, but feel free to change it later.

> > +	taskset "$1" echo 1 > "$lasysfsdir"/capture || fail "Capture error! Check kernel log"
> 
> Shouldn't this function setup signal TRAPs?

To do what?

> $@ is better, actually one should never use $*.

What difference does it make when expanding into a string?

> Wondering, shouldn't be a simple validator before start that we have commands
> present, such as zip?

This is what the variable 'neededcmds' is for...

Kind regards,

   Wolfram


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Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Andy Shevchenko]

On Sat, Dec 18, 2021 at 11:21 PM Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:

> > > +Result is a .sr file to be consumed with PulseView or sigrok-cli from the free
> > > +`sigrok`_ project. It is a zip file which also contains the binary sample data
> > > +which may be consumed by other software. The filename is the logic analyzer
> > > +instance name plus a since-epoch timestamp.
> > > +
> > > +.. _sigrok: https://sigrok.org/
> >
> > Alas, yet another tool required... (Sad thoughts since recently has installed
> > PicoScope software).
>
> ? For sure, another tool is required. Do you want the analyzer itself to
> output pretty SVG files? :)

I mean that there are similar functionality in different tools and for
one purpose you need one, for another another and there is no format
file convertors available (as far as my shallow googling shows).

...

> > > +   if (ret >= 0 && ret != priv->descs->ndescs)
> >
> > > +           ret = -ENODATA;
> >
> > Don't remember if we already discussed this error code, but data is there,
> > it's not correct. EBADSLT? EBADR? ECHRNG?
>
> In your V1 review, you suggested -ENODATA. I will pick yet another one,
> but it really matters zero in practice.

Ah, okay, then choose the one you think fits most.

...

> > Do we really need the 'probe%02u=' part? It's redundant since it may be derived
> > from the line number of the output (and it always in [1..ndescs+1]).
>
> It makes creating the .sr-file a lot easier. If you feel strong about
> it, then you can later remove it and also update the script, I'd say.

No strong opinion, I don't know the Sigrok tool and its file format,
so I can't tell if it makes sense or doesn't.

...

> > `> /dev/null 2>&1` is idiomatic. And I think there is actually a subtle
> > difference between two.
>
> What is the difference? Does it matter here?

I'm a bit lost in the context here, but the ' > /dev/null 2>&1' means
to redirect stdout to the /dev/null followed by redirecting stderr to
stdout (which is redirected to /dev/null). The other construction
might have side effects IIRC.

...

> > > +                   [ "$chan" != "$elem" ] && [ "$chan" -le $max_chans ] || fail "Trigger syntax error: $elem"
> >
> > No need to execute `test` twice:
> >
> >                       [ "$chan" != "$elem" -a "$chan" -le $max_chans ] || fail "Trigger syntax error: $elem"
>
> I read that '-a' and '-o' are deprecated. Dunno where but looking again
> I found this: https://stackoverflow.com/questions/20449680/boolean-operators-a-o-in-bash

The SO talks about _bash_, your script is a plain Shell one, right?
And for the record, I don't like bashisms in some generic code, like
the one we use with Linux kernel.

...

> > > +   taskset "$1" echo 1 > "$lasysfsdir"/capture || fail "Capture error! Check kernel log"
> >
> > Shouldn't this function setup signal TRAPs?
>
> To do what?

To clean up the garbage it may leave in case of the interrupted run, no?

...

> > $@ is better, actually one should never use $*.
>
> What difference does it make when expanding into a string?

The difference is on how the  "foo bar" (with double quotes!) will be
represented. In your case it will be translated as "foo" and "bar", in
the case I'm saying it will be "foo bar".

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 2449 bytes --]

Hi Andy,

> I mean that there are similar functionality in different tools and for
> one purpose you need one, for another another and there is no format
> file convertors available (as far as my shallow googling shows).

Yes, this is a truth I can't change. So, I chose the Free Software
solution, so the format is at least documented. Also, you could just try
sigrok and pulseview, it has a nice set of protocol decoders. GTKWave
should be able to use the binary data inside the .sr IIRC. For other
software, you can at least write a converter because the format is open.

> > In your V1 review, you suggested -ENODATA. I will pick yet another one,
> > but it really matters zero in practice.
> 
> Ah, okay, then choose the one you think fits most.

I took -EBADR now.

> > What is the difference? Does it matter here?
> 
> I'm a bit lost in the context here, but the ' > /dev/null 2>&1' means
> to redirect stdout to the /dev/null followed by redirecting stderr to
> stdout (which is redirected to /dev/null). The other construction
> might have side effects IIRC.

Andy, *if* there is a side effect, I will happily fix it. But "it might
have a side effect IIRC" leaves all the detective work to me and I am
not short of other action items. Especially because this is not a
critical path.

> > I read that '-a' and '-o' are deprecated. Dunno where but looking again
> > I found this: https://stackoverflow.com/questions/20449680/boolean-operators-a-o-in-bash
> 
> The SO talks about _bash_, your script is a plain Shell one, right?

It talks about being deprecated in POSIX, so quite the opposite of a
bashism, I'd say.

> > > > +   taskset "$1" echo 1 > "$lasysfsdir"/capture || fail "Capture error! Check kernel log"
> > >
> > > Shouldn't this function setup signal TRAPs?
> >
> > To do what?
> 
> To clean up the garbage it may leave in case of the interrupted run, no?

I don't see any? Which ones do you have in mind?

> > > $@ is better, actually one should never use $*.
> >
> > What difference does it make when expanding into a string?
> 
> The difference is on how the  "foo bar" (with double quotes!) will be
> represented. In your case it will be translated as "foo" and "bar", in
> the case I'm saying it will be "foo bar".

I very well know the difference. I was interested in what difference you
see when they get expanded into a string?

Happy hacking,

   Wolfram


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Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Linus Walleij]

Hi Wolfram!

I like this patch.

On Tue, Nov 23, 2021 at 5:49 PM Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:

> +Introduction
> +============
> +
> +This document briefly describes how to run the GPIO based in-kernel sloppy
> +logic analyzer running on an isolated CPU.
> +
> +Note that this is a last resort analyzer which can be affected by latencies,
> +non-deterministic code paths and non-maskable interrupts. It is called 'sloppy'
> +for a reason. However, for e.g. remote development, it may be useful to get a
> +first view and aid further debugging.

Maybe a small paragraph first saying what this is, the usecase (feel
free to steal,
rewrite etc):

The sloppy logic analyzer will utilize a few GPIO lines in input mode on a
system to rapidly sample these digital lines, which will, if the
Nyquist criteria
is met, result in a time series log with approximate waveforms as they appeared
on these lines.

One way to use it is to analyze external traffic connected to these GPIO
lines with wires (i.e. digital probes), acting as a common logic analyzer.

Another thing it can do is to snoop on on-chip peripherals if the I/O cells of
these peripherals can be used in GPIO input mode at the same time as they
are being used as inputs or outputs for the peripheral, for example it would be
possible to scale down the speed of a certain MMC controller and snoop
the traffic between the MMC controller and the SD card by the sloppy
logic analyzer. In the pin control subsystem such pin controllers are
called "non-strict": a certain pin can be used with a certain peripheral and
as a GPIO input line at the same time.

Yours,
Linus Walleij

Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Wolfram Sang]

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Hi Linus!

> I like this patch.

I am glad!

> 
> Maybe a small paragraph first saying what this is, the usecase (feel
> free to steal, rewrite etc):
> 
> The sloppy logic analyzer will utilize a few GPIO lines in input mode
> on a system to rapidly sample these digital lines, which will, if the
> Nyquist criteria is met, result in a time series log with approximate
> waveforms as they appeared on these lines.
> 
> One way to use it is to analyze external traffic connected to these
> GPIO lines with wires (i.e. digital probes), acting as a common logic
> analyzer.

Well, frankly, with the driver depending on EXPERT, this paragraph seems
a tad superfluous to me. But as it came for free and won't hurt, I took
the liberty to add this to the beginning of the documentation.

> Another thing it can do is to snoop on on-chip peripherals if the I/O
> cells of these peripherals can be used in GPIO input mode at the same
> time as they are being used as inputs or outputs for the peripheral,
> for example it would be possible to scale down the speed of a certain
> MMC controller and snoop the traffic between the MMC controller and
> the SD card by the sloppy logic analyzer. In the pin control subsystem
> such pin controllers are called "non-strict": a certain pin can be
> used with a certain peripheral and as a GPIO input line at the same
> time.

Thanks for pointing out the 'strict' mode. I actually did snoop pins
muxed to I2C but I had to use a gpiolib hack for it assuming this was
not supported otherwise. Now, I have a one-liner for the Renesas pinctrl
driver which makes things work as well. I will work this out with Geert
hopefully. Would be really great to have this feature without my hack!

That being said, the paragraph above is a bit too long for my taste,
I'll see if I can make it more concise. But it should be there, yes.

Thanks for your support!

Happy hacking,

   Wolfram


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Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Bartosz Golaszewski]

On Tue, Nov 23, 2021 at 5:49 PM Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
>
> This is a sloppy logic analyzer using GPIOs. It comes with a script to
> isolate a CPU for polling. While this is definitely not a production
> level analyzer, it can be a helpful first view when remote debugging.
> Read the documentation for details.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Hi Wolfram!

I'm seeing you're using debugfs for this module (both for
configuration as well as control). How about using configfs + sysfs?
I'd argue that debugfs isn't really the right interface for a useful
tool that is this LA.

Bart

Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Wolfram Sang]

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> I'd argue that debugfs isn't really the right interface for a useful
> tool that is this LA.

I have to disagree. This is a kind-of logic analyzer, it is sloppy. To
emphasize it is for debugging only, I think debugfs is the proper place
for it.

But thanks for finding it useful :)


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Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Geert Uytterhoeven]

Hi Wolfram,

On Tue, Nov 23, 2021 at 5:49 PM Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
> This is a sloppy logic analyzer using GPIOs. It comes with a script to
> isolate a CPU for polling. While this is definitely not a production
> level analyzer, it can be a helpful first view when remote debugging.
> Read the documentation for details.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -74,6 +74,7 @@ obj-$(CONFIG_GPIO_IT87)                       += gpio-it87.o
>  obj-$(CONFIG_GPIO_IXP4XX)              += gpio-ixp4xx.o
>  obj-$(CONFIG_GPIO_JANZ_TTL)            += gpio-janz-ttl.o
>  obj-$(CONFIG_GPIO_KEMPLD)              += gpio-kempld.o
> +obj-$(CONFIG_GPIO_SLOPPY_LOGIC_ANALYZER) += gpio-sloppy-logic-analyzer.o
>  obj-$(CONFIG_GPIO_LOGICVC)             += gpio-logicvc.o
>  obj-$(CONFIG_GPIO_LOONGSON1)           += gpio-loongson1.o
>  obj-$(CONFIG_GPIO_LOONGSON)            += gpio-loongson.o

(noticed while resolving a merge conflict with the out-of-tree
 gpio-litex)

Please preserve sort order, cfr. the (hilarious?) comment at the top
of the list:

    # Device drivers. Generally keep list sorted alphabetically
    obj-$(CONFIG_GPIO_REGMAP)       += gpio-regmap.o
    obj-$(CONFIG_GPIO_GENERIC)      += gpio-generic.o

    # directly supported by gpio-generic

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling

[Wolfram Sang]

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> Please preserve sort order, cfr. the (hilarious?) comment at the top
> of the list:

Ouch, yes. That's what you get for a last minute rename. Fixed in v6!


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