diff options
| -rw-r--r-- | Documentation/i2c/gpio-fault-injection | 19 | ||||
| -rw-r--r-- | drivers/i2c/busses/i2c-gpio.c | 21 |
2 files changed, 40 insertions, 0 deletions
diff --git a/Documentation/i2c/gpio-fault-injection b/Documentation/i2c/gpio-fault-injection index 37542461cea4..a4ce62090fd5 100644 --- a/Documentation/i2c/gpio-fault-injection +++ b/Documentation/i2c/gpio-fault-injection @@ -60,3 +60,22 @@ 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. +"incomplete_write_byte" +----------------------- + +Similar to above, this file is write only and you need to write the address of +an existing I2C client device to it. + +The injector will again stop at one ACK phase, so the device will keep SDA low +because it acknowledges data. However, there are two differences compared to +'incomplete_address_phase': + +a) the message sent out will be a write message +b) after the address byte, a 0x00 byte will be transferred. Then, stop at ACK. + +This is a highly delicate state, the device is set up to write any data to +register 0x00 (if it has registers) when further clock pulses happen on SCL. +This is why bus recovery (up to 9 clock pulses) must either check SDA or send +additional STOP conditions to ensure the bus has been released. Otherwise +random data will be written to a device! + diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c index b69bb46bdb9d..ac00b8e08251 100644 --- a/drivers/i2c/busses/i2c-gpio.c +++ b/drivers/i2c/busses/i2c-gpio.c @@ -143,6 +143,25 @@ static int fops_incomplete_addr_phase_set(void *data, u64 addr) } DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n"); +static int fops_incomplete_write_byte_set(void *data, u64 addr) +{ + struct i2c_gpio_private_data *priv = data; + u32 pattern; + + if (addr > 0x7f) + return -EINVAL; + + /* ADDR (7 bit) + WR (1 bit) + Client ACK (1 bit) */ + pattern = (addr << 2) | 1; + /* 0x00 (8 bit) + Client ACK, keep SDA hi (1 bit) */ + pattern = (pattern << 9) | 1; + + i2c_gpio_incomplete_transfer(priv, pattern, 18); + + return 0; +} +DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_write_byte, NULL, fops_incomplete_write_byte_set, "%llu\n"); + static void i2c_gpio_fault_injector_init(struct platform_device *pdev) { struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev); @@ -166,6 +185,8 @@ static void i2c_gpio_fault_injector_init(struct platform_device *pdev) debugfs_create_file_unsafe("sda", 0600, priv->debug_dir, priv, &fops_sda); debugfs_create_file_unsafe("incomplete_address_phase", 0200, priv->debug_dir, priv, &fops_incomplete_addr_phase); + debugfs_create_file_unsafe("incomplete_write_byte", 0200, priv->debug_dir, + priv, &fops_incomplete_write_byte); } static void i2c_gpio_fault_injector_exit(struct platform_device *pdev) |