i2c: gpio: add fault injector
Add fault injection capabilities to the i2c-gpio driver. When connected to another I2C bus, it can create unusual states which the other I2C bus master driver needs to handle. Only for debugging! Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
This commit is contained in:
parent
4d67c2e7f6
commit
14911c6f48
54
Documentation/i2c/gpio-fault-injection
Normal file
54
Documentation/i2c/gpio-fault-injection
Normal file
|
@ -0,0 +1,54 @@
|
|||
Linux I2C fault injection
|
||||
=========================
|
||||
|
||||
The GPIO based I2C bus master driver can be configured to provide fault
|
||||
injection capabilities. It is then meant to be connected to another I2C bus
|
||||
which is driven by the I2C bus master driver under test. The GPIO fault
|
||||
injection driver can create special states on the bus which the other I2C bus
|
||||
master driver should handle gracefully.
|
||||
|
||||
Once the Kconfig option I2C_GPIO_FAULT_INJECTOR is enabled, there will be an
|
||||
'i2c-fault-injector' subdirectory in the Kernel debugfs filesystem, usually
|
||||
mounted at /sys/kernel/debug. There will be a separate subdirectory per GPIO
|
||||
driven I2C bus. Each subdirectory will contain files to trigger the fault
|
||||
injection. They will be described now along with their intended use-cases.
|
||||
|
||||
"scl"
|
||||
-----
|
||||
|
||||
By reading this file, you get the current state of SCL. By writing, you can
|
||||
change its state to either force it low or to release it again. So, by using
|
||||
"echo 0 > scl" you force SCL low and thus, no communication will be possible
|
||||
because the bus master under test will not be able to clock. It should detect
|
||||
the condition of SCL being unresponsive and report an error to the upper
|
||||
layers.
|
||||
|
||||
"sda"
|
||||
-----
|
||||
|
||||
By reading this file, you get the current state of SDA. By writing, you can
|
||||
change its state to either force it low or to release it again. So, by using
|
||||
"echo 0 > sda" you force SDA low and thus, data cannot be transmitted. The bus
|
||||
master under test should detect this condition and trigger a bus recovery (see
|
||||
I2C specification version 4, section 3.1.16) using the helpers of the Linux I2C
|
||||
core (see 'struct bus_recovery_info'). However, the bus recovery will not
|
||||
succeed because SDA is still pinned low until you manually release it again
|
||||
with "echo 1 > sda". A test with an automatic release can be done with the
|
||||
'incomplete_transfer' file.
|
||||
|
||||
"incomplete_transfer"
|
||||
---------------------
|
||||
|
||||
This file is write only and you need to write the address of an existing I2C
|
||||
client device to it. Then, a transfer to this device will be started, but it
|
||||
will stop at the ACK phase after the address of the client has been
|
||||
transmitted. Because the device will ACK its presence, this results in SDA
|
||||
being pulled low by the device while SCL is high. So, similar to the "sda" file
|
||||
above, the bus master under test should detect this condition and try a bus
|
||||
recovery. This time, however, it should succeed and the device should release
|
||||
SDA after toggling SCL. Please note: there are I2C client devices which detect
|
||||
a stuck SDA on their side and release it on their own after a few milliseconds.
|
||||
Also, there are external devices deglitching and monitoring the I2C bus. They
|
||||
can also detect a stuck SDA and will init a bus recovery on their own. If you
|
||||
want to implement bus recovery in a bus master driver, make sure you checked
|
||||
your hardware setup carefully before.
|
|
@ -603,6 +603,14 @@ config I2C_GPIO
|
|||
This is a very simple bitbanging I2C driver utilizing the
|
||||
arch-neutral GPIO API to control the SCL and SDA lines.
|
||||
|
||||
config I2C_GPIO_FAULT_INJECTOR
|
||||
bool "GPIO-based fault injector"
|
||||
depends on I2C_GPIO
|
||||
help
|
||||
This adds some functionality to the i2c-gpio driver which can inject
|
||||
faults to an I2C bus, so another bus master can be stress-tested.
|
||||
This is for debugging. If unsure, say 'no'.
|
||||
|
||||
config I2C_HIGHLANDER
|
||||
tristate "Highlander FPGA SMBus interface"
|
||||
depends on SH_HIGHLANDER
|
||||
|
|
|
@ -7,6 +7,8 @@
|
|||
* it under the terms of the GNU General Public License version 2 as
|
||||
* published by the Free Software Foundation.
|
||||
*/
|
||||
#include <linux/debugfs.h>
|
||||
#include <linux/delay.h>
|
||||
#include <linux/i2c.h>
|
||||
#include <linux/i2c-algo-bit.h>
|
||||
#include <linux/i2c-gpio.h>
|
||||
|
@ -23,6 +25,9 @@ struct i2c_gpio_private_data {
|
|||
struct i2c_adapter adap;
|
||||
struct i2c_algo_bit_data bit_data;
|
||||
struct i2c_gpio_platform_data pdata;
|
||||
#ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
|
||||
struct dentry *debug_dir;
|
||||
#endif
|
||||
};
|
||||
|
||||
/*
|
||||
|
@ -64,6 +69,108 @@ static int i2c_gpio_getscl(void *data)
|
|||
return gpiod_get_value(priv->scl);
|
||||
}
|
||||
|
||||
#ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
|
||||
static struct dentry *i2c_gpio_debug_dir;
|
||||
|
||||
#define setsda(bd, val) ((bd)->setsda((bd)->data, val))
|
||||
#define setscl(bd, val) ((bd)->setscl((bd)->data, val))
|
||||
#define getsda(bd) ((bd)->getsda((bd)->data))
|
||||
#define getscl(bd) ((bd)->getscl((bd)->data))
|
||||
|
||||
#define WIRE_ATTRIBUTE(wire) \
|
||||
static int fops_##wire##_get(void *data, u64 *val) \
|
||||
{ \
|
||||
struct i2c_gpio_private_data *priv = data; \
|
||||
\
|
||||
i2c_lock_adapter(&priv->adap); \
|
||||
*val = get##wire(&priv->bit_data); \
|
||||
i2c_unlock_adapter(&priv->adap); \
|
||||
return 0; \
|
||||
} \
|
||||
static int fops_##wire##_set(void *data, u64 val) \
|
||||
{ \
|
||||
struct i2c_gpio_private_data *priv = data; \
|
||||
\
|
||||
i2c_lock_adapter(&priv->adap); \
|
||||
set##wire(&priv->bit_data, val); \
|
||||
i2c_unlock_adapter(&priv->adap); \
|
||||
return 0; \
|
||||
} \
|
||||
DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%llu\n")
|
||||
|
||||
WIRE_ATTRIBUTE(scl);
|
||||
WIRE_ATTRIBUTE(sda);
|
||||
|
||||
static int fops_incomplete_transfer_set(void *data, u64 addr)
|
||||
{
|
||||
struct i2c_gpio_private_data *priv = data;
|
||||
struct i2c_algo_bit_data *bit_data = &priv->bit_data;
|
||||
int i, pattern;
|
||||
|
||||
if (addr > 0x7f)
|
||||
return -EINVAL;
|
||||
|
||||
/* ADDR (7 bit) + RD (1 bit) + SDA hi (1 bit) */
|
||||
pattern = (addr << 2) | 3;
|
||||
|
||||
i2c_lock_adapter(&priv->adap);
|
||||
|
||||
/* START condition */
|
||||
setsda(bit_data, 0);
|
||||
udelay(bit_data->udelay);
|
||||
|
||||
/* Send ADDR+RD, request ACK, don't send STOP */
|
||||
for (i = 8; i >= 0; i--) {
|
||||
setscl(bit_data, 0);
|
||||
udelay(bit_data->udelay / 2);
|
||||
setsda(bit_data, (pattern >> i) & 1);
|
||||
udelay((bit_data->udelay + 1) / 2);
|
||||
setscl(bit_data, 1);
|
||||
udelay(bit_data->udelay);
|
||||
}
|
||||
|
||||
i2c_unlock_adapter(&priv->adap);
|
||||
|
||||
return 0;
|
||||
}
|
||||
DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_transfer, NULL, fops_incomplete_transfer_set, "%llu\n");
|
||||
|
||||
static void i2c_gpio_fault_injector_init(struct platform_device *pdev)
|
||||
{
|
||||
struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
|
||||
|
||||
/*
|
||||
* If there will be a debugfs-dir per i2c adapter somewhen, put the
|
||||
* 'fault-injector' dir there. Until then, we have a global dir with
|
||||
* all adapters as subdirs.
|
||||
*/
|
||||
if (!i2c_gpio_debug_dir) {
|
||||
i2c_gpio_debug_dir = debugfs_create_dir("i2c-fault-injector", NULL);
|
||||
if (!i2c_gpio_debug_dir)
|
||||
return;
|
||||
}
|
||||
|
||||
priv->debug_dir = debugfs_create_dir(pdev->name, i2c_gpio_debug_dir);
|
||||
if (!priv->debug_dir)
|
||||
return;
|
||||
|
||||
debugfs_create_file_unsafe("scl", 0600, priv->debug_dir, priv, &fops_scl);
|
||||
debugfs_create_file_unsafe("sda", 0600, priv->debug_dir, priv, &fops_sda);
|
||||
debugfs_create_file_unsafe("incomplete_transfer", 0200, priv->debug_dir,
|
||||
priv, &fops_incomplete_transfer);
|
||||
}
|
||||
|
||||
static void i2c_gpio_fault_injector_exit(struct platform_device *pdev)
|
||||
{
|
||||
struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
|
||||
|
||||
debugfs_remove_recursive(priv->debug_dir);
|
||||
}
|
||||
#else
|
||||
static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {}
|
||||
static inline void i2c_gpio_fault_injector_exit(struct platform_device *pdev) {}
|
||||
#endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/
|
||||
|
||||
static void of_i2c_gpio_get_props(struct device_node *np,
|
||||
struct i2c_gpio_platform_data *pdata)
|
||||
{
|
||||
|
@ -228,6 +335,8 @@ static int i2c_gpio_probe(struct platform_device *pdev)
|
|||
pdata->scl_is_output_only
|
||||
? ", no clock stretching" : "");
|
||||
|
||||
i2c_gpio_fault_injector_init(pdev);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
@ -236,6 +345,8 @@ static int i2c_gpio_remove(struct platform_device *pdev)
|
|||
struct i2c_gpio_private_data *priv;
|
||||
struct i2c_adapter *adap;
|
||||
|
||||
i2c_gpio_fault_injector_exit(pdev);
|
||||
|
||||
priv = platform_get_drvdata(pdev);
|
||||
adap = &priv->adap;
|
||||
|
||||
|
|
Loading…
Reference in a new issue