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Message-Id: <20250806-refactor-add-i2c-tracepoints-v1-1-d1d39bd6fb57@gmail.com>
Date: Wed, 06 Aug 2025 12:14:32 +0300
From: Mohammad Gomaa <midomaxgomaa@...il.com>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>,
Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org, kenalba@...gle.com,
hbarnor@...omium.org, rayxu@...gle.com,
Mohammad Gomaa <midomaxgomaa@...il.com>
Subject: [PATCH WIP] i2c: add tracepoints to aid debugging in i2c-core-base
Add tracepoints to i2c-core-base.c file to help trace
and debug I2C device probe failures.
The new trace points are:
- i2c_device_probe_debug: records non-failure routines
e.g. IRQ 0.
- i2c_device_probe_failed: records failure routines e.g.
failure to set default clocks.
To support operation of these tracepoints a variable
was added to record reason for debug and failure.
Signed-off-by: Mohammad Gomaa <midomaxgomaa@...il.com>
---
Hello,
This patch adds tracepoints to i2c-core-base to aid with debugging I2C probing failrues.
The motivation for this comes from my work in Google Summer of Code (GSoC) 2025:
"ChromeOS Platform Input Device Quality Monitoring"
https://summerofcode.withgoogle.com/programs/2025/projects/uCdIgK7K
This is my first submission to the Linux kernel, so any feedback is welcome.
---
drivers/i2c/i2c-core-base.c | 61 ++++++++++++++++++++++++++++++++++-----------
include/trace/events/i2c.h | 23 +++++++++++++++++
2 files changed, 70 insertions(+), 14 deletions(-)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index ecca8c006b020379fb53293b20ab09ba25314609..c145af56a17d74117985430d04b75fff5b45b9b2 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -495,6 +495,8 @@ static int i2c_device_probe(struct device *dev)
struct i2c_driver *driver;
bool do_power_on;
int status;
+ const char *reason = NULL;
+ bool has_id_table, has_acpi_match, has_of_match;
if (!client)
return 0;
@@ -509,38 +511,54 @@ static int i2c_device_probe(struct device *dev)
/* Keep adapter active when Host Notify is required */
pm_runtime_get_sync(&client->adapter->dev);
irq = i2c_smbus_host_notify_to_irq(client);
+ reason = "IRQ 0: could not get irq from Host Notify";
} else if (is_of_node(fwnode)) {
irq = fwnode_irq_get_byname(fwnode, "irq");
if (irq == -EINVAL || irq == -ENODATA)
irq = fwnode_irq_get(fwnode, 0);
+ reason = "IRQ 0: could not get irq from OF";
} else if (is_acpi_device_node(fwnode)) {
bool wake_capable;
irq = i2c_acpi_get_irq(client, &wake_capable);
if (irq > 0 && wake_capable)
client->flags |= I2C_CLIENT_WAKE;
+ reason = "IRQ 0: could not get irq from ACPI";
}
if (irq == -EPROBE_DEFER) {
status = dev_err_probe(dev, irq, "can't get irq\n");
+ reason = "IRQ 0: could not get IRQ due to EPROBE_DEFER";
goto put_sync_adapter;
}
- if (irq < 0)
+ if (irq < 0) {
+ trace_i2c_device_probe_debug(dev, reason);
irq = 0;
+ }
client->irq = irq;
}
driver = to_i2c_driver(dev->driver);
+ has_id_table = driver->id_table;
+ has_acpi_match = acpi_driver_match_device(dev, dev->driver);
+ has_of_match = i2c_of_match_device(dev->driver->of_match_table, client);
+
+ if (!has_id_table)
+ trace_i2c_device_probe_debug(dev, "no I2C ID table");
+ if (!has_acpi_match)
+ trace_i2c_device_probe_debug(dev, "ACPI ID table mismatch");
+ if (!has_of_match)
+ trace_i2c_device_probe_debug(dev, "OF ID table mismatch");
+
/*
* An I2C ID table is not mandatory, if and only if, a suitable OF
* or ACPI ID table is supplied for the probing device.
*/
- if (!driver->id_table &&
- !acpi_driver_match_device(dev, dev->driver) &&
- !i2c_of_match_device(dev->driver->of_match_table, client)) {
+ if (!has_id_table && !has_acpi_match && !has_of_match) {
status = -ENODEV;
+ reason = "no I2C ID table and no ACPI/OF match";
goto put_sync_adapter;
}
@@ -550,47 +568,60 @@ static int i2c_device_probe(struct device *dev)
wakeirq = fwnode_irq_get_byname(fwnode, "wakeup");
if (wakeirq == -EPROBE_DEFER) {
status = dev_err_probe(dev, wakeirq, "can't get wakeirq\n");
+ reason = "get wake IRQ due to EPROBE_DEFER";
goto put_sync_adapter;
}
device_init_wakeup(&client->dev, true);
- if (wakeirq > 0 && wakeirq != client->irq)
+ if (wakeirq > 0 && wakeirq != client->irq) {
status = dev_pm_set_dedicated_wake_irq(dev, wakeirq);
- else if (client->irq > 0)
+ reason = "failed to set dedicated wakeup IRQ";
+ } else if (client->irq > 0) {
status = dev_pm_set_wake_irq(dev, client->irq);
- else
+ reason = "failed to set wakeup IRQ";
+ } else {
status = 0;
+ reason = "no IRQ";
+ }
- if (status)
+ if (status) {
dev_warn(&client->dev, "failed to set up wakeup irq\n");
+ trace_i2c_device_probe_debug(&client->dev, reason);
+ }
}
dev_dbg(dev, "probe\n");
status = of_clk_set_defaults(to_of_node(fwnode), false);
- if (status < 0)
+ if (status < 0) {
+ reason = "set default clocks";
goto err_clear_wakeup_irq;
-
+ }
do_power_on = !i2c_acpi_waive_d0_probe(dev);
status = dev_pm_domain_attach(&client->dev, do_power_on ? PD_FLAG_ATTACH_POWER_ON : 0);
- if (status)
+ if (status) {
+ reason = "attach PM domain";
goto err_clear_wakeup_irq;
-
+ }
client->devres_group_id = devres_open_group(&client->dev, NULL,
GFP_KERNEL);
if (!client->devres_group_id) {
status = -ENOMEM;
+ reason = "open devres group";
goto err_detach_pm_domain;
}
client->debugfs = debugfs_create_dir(dev_name(&client->dev),
client->adapter->debugfs);
- if (driver->probe)
+ if (driver->probe) {
status = driver->probe(client);
- else
+ reason = "specific driver probe failed";
+ } else {
status = -EINVAL;
+ reason = "no probe defined";
+ }
/*
* Note that we are not closing the devres group opened above so
@@ -617,6 +648,8 @@ static int i2c_device_probe(struct device *dev)
if (client->flags & I2C_CLIENT_HOST_NOTIFY)
pm_runtime_put_sync(&client->adapter->dev);
+ trace_i2c_device_probe_failed(&client->dev, status, reason);
+
return status;
}
diff --git a/include/trace/events/i2c.h b/include/trace/events/i2c.h
index 142a23c6593c611de9abc2a89a146b95550b23cd..1a08800dcdd760e2a5a40b76c4a244e1b4ef3b1e 100644
--- a/include/trace/events/i2c.h
+++ b/include/trace/events/i2c.h
@@ -16,6 +16,29 @@
/*
* drivers/i2c/i2c-core-base.c
*/
+TRACE_EVENT(i2c_device_probe_debug,
+ TP_PROTO(struct device *dev, const char *message),
+ TP_ARGS(dev, message),
+ TP_STRUCT__entry(__string(devname, dev_name(dev)) __string(message, message)),
+ TP_fast_assign(__assign_str(devname); __assign_str(message);),
+ TP_printk("device=%s: %s", __get_str(devname), __get_str(message))
+);
+
+TRACE_EVENT(i2c_device_probe_failed,
+ TP_PROTO(struct device *dev, int status, const char *reason),
+ TP_ARGS(dev, status, reason),
+ TP_STRUCT__entry(__string(dev_name, dev_name(dev))
+ __field(int, status)
+ __string(reason, reason)),
+ TP_fast_assign(__assign_str(dev_name);
+ __entry->status = status;
+ __assign_str(reason);),
+ TP_printk("failed to probe %s: %d (%s)",
+ __get_str(dev_name),
+ __entry->status,
+ __get_str(reason))
+);
+
extern int i2c_transfer_trace_reg(void);
extern void i2c_transfer_trace_unreg(void);
---
base-commit: 7e161a991ea71e6ec526abc8f40c6852ebe3d946
change-id: 20250806-refactor-add-i2c-tracepoints-b6e2b92d4cd9
Best regards,
--
Mohammad Gomaa <midomaxgomaa@...il.com>
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