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-rw-r--r--Documentation/i2c/gpio-fault-injection19
-rw-r--r--drivers/i2c/busses/i2c-gpio.c21
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)