diff mbox series

[2/2] i2c: gpio: fault-injector: add incomplete_write_byte

Message ID 20180604143252.325-3-wsa+renesas@sang-engineering.com
State Superseded
Headers show
Series i2c: gpio: fault-injector: add new injector | expand

Commit Message

Wolfram Sang June 4, 2018, 2:32 p.m. UTC 
Add another injector for an incomplete transfer. As mentioned in the
docs, this one is important to check bus recovery algorithms with it.
Otherwise random data may be sent to devices!

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 Documentation/i2c/gpio-fault-injection | 15 +++++++++++++++
 drivers/i2c/busses/i2c-gpio.c          | 21 +++++++++++++++++++++
 2 files changed, 36 insertions(+)
diff mbox series

Patch

diff --git a/Documentation/i2c/gpio-fault-injection b/Documentation/i2c/gpio-fault-injection
index ce89a71547d2..5ceca19b6030 100644
--- a/Documentation/i2c/gpio-fault-injection
+++ b/Documentation/i2c/gpio-fault-injection
@@ -60,3 +60,18 @@  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 the ACK phase, so the device will keep SDA low
+because it acknowledges data. However, there are two differences: a) the
+message sent out will be a write message b) after the address byte, an
+additional 0x00 byte will be transferred. This is a 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, 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 cbbb7b201d59..52265572e317 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)