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authorWolfram Sang <wsa+renesas@sang-engineering.com>2024-06-20 11:41:58 +0200
committerBartosz Golaszewski <bartosz.golaszewski@linaro.org>2024-07-01 10:54:11 +0200
commit7828b7bbbf2074dd7dd14d87f50bc5ce9036d692 (patch)
tree4274f1036aab287eff744f22947dad42ee21d061 /drivers/gpio
parentDocumentation: gpio: Reconfiguration with unset direction (uAPI v2) (diff)
downloadlinux-7828b7bbbf2074dd7dd14d87f50bc5ce9036d692.tar.xz
linux-7828b7bbbf2074dd7dd14d87f50bc5ce9036d692.zip
gpio: add sloppy logic analyzer using polling
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> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Link: https://lore.kernel.org/r/20240620094159.6785-2-wsa+renesas@sang-engineering.com [Bartosz: moved the Kconfig entry into a different category] Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Diffstat (limited to 'drivers/gpio')
-rw-r--r--drivers/gpio/Kconfig19
-rw-r--r--drivers/gpio/Makefile1
-rw-r--r--drivers/gpio/gpio-sloppy-logic-analyzer.c344
3 files changed, 364 insertions, 0 deletions
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index dfb8dc850f3c..2b9bd1893863 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1891,4 +1891,23 @@ config GPIO_SIM
endmenu
+menu "GPIO Debugging utilities"
+
+config GPIO_SLOPPY_LOGIC_ANALYZER
+ tristate "Sloppy GPIO logic analyzer"
+ depends on (GPIOLIB || COMPILE_TEST) && CPUSETS && DEBUG_FS && 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 e2a53013780e..9889f5b962bf 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -150,6 +150,7 @@ obj-$(CONFIG_GPIO_SIFIVE) += gpio-sifive.o
obj-$(CONFIG_GPIO_SIM) += gpio-sim.o
obj-$(CONFIG_GPIO_SIOX) += gpio-siox.o
obj-$(CONFIG_GPIO_SL28CPLD) += gpio-sl28cpld.o
+obj-$(CONFIG_GPIO_SLOPPY_LOGIC_ANALYZER) += gpio-sloppy-logic-analyzer.o
obj-$(CONFIG_GPIO_SODAVILLE) += gpio-sodaville.o
obj-$(CONFIG_GPIO_SPEAR_SPICS) += gpio-spear-spics.o
obj-$(CONFIG_GPIO_SPRD) += gpio-sprd.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..aed6d1f6cfc3
--- /dev/null
+++ b/drivers/gpio/gpio-sloppy-logic-analyzer.c
@@ -0,0 +1,344 @@
+// 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/device.h>
+#include <linux/err.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/types.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 blob_lock; /* serialize access to the blob (data) */
+ 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->blob_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 out;
+ }
+
+ priv->acq_delay = ktime_sub(ktime_get(), start_time) / GPIO_LA_NUM_TESTS;
+ if (priv->delay_ns < priv->acq_delay) {
+ ret = -ERANGE;
+ goto out;
+ }
+
+ 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 out;
+
+ 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 out;
+
+ la_buf[priv->buf_idx++] = state;
+ ndelay(delay);
+ }
+out:
+ 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->blob_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->blob_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->blob_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;
+
+ devm_mutex_init(dev, &priv->blob_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 = -EBADR;
+ 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);
+
+ return 0;
+}
+
+static void gpio_la_poll_remove(struct platform_device *pdev)
+{
+ struct gpio_la_poll_priv *priv = platform_get_drvdata(pdev);
+
+ mutex_lock(&priv->blob_lock);
+ debugfs_remove_recursive(priv->debug_dir);
+ mutex_unlock(&priv->blob_lock);
+}
+
+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_new = 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);
+}
+/*
+ * Non-strict pin controllers can read GPIOs while being muxed to something else.
+ * To support that, we need to claim GPIOs before further pinmuxing happens. So,
+ * we probe early using 'late_initcall'
+ */
+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");