Commit 16d55daa authored by Wolfram Sang's avatar Wolfram Sang Committed by Wolfram Sang
Browse files

i2c: gpio: fault-injector: refactor incomplete transfer 



Make the incomplete_transfer routine reusable, so we can add other test
cases with different patterns later. Prepare the docs for that, too.

Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent d07bdbc0

Documentation/i2c/gpio-fault-injection

+19 −11
Original line number Diff line number Diff line
@@ -34,21 +34,29 @@ 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.

following class of fault injectors.



"incomplete_transfer"

---------------------

Introduction to incomplete transfers

------------------------------------



The following fault injectors create situations where SDA will be held low by a

device. Bus recovery should be able to fix these situations. But 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 might be an external

device deglitching and monitoring the I2C bus. It could also detect a stuck SDA

and will init a bus recovery on its own. If you want to implement bus recovery

in a bus master driver, make sure you checked your hardware setup for such

devices before. And always verify with a scope or logic analyzer!



"incomplete_address_phase"

--------------------------



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

client device to it. Then, a read 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.
 
SDA after toggling SCL.

drivers/i2c/busses/i2c-gpio.c

+22 −14
Original line number Diff line number Diff line
@@ -101,17 +101,11 @@ DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%ll 
WIRE_ATTRIBUTE(scl);

WIRE_ATTRIBUTE(sda);



static int fops_incomplete_transfer_set(void *data, u64 addr)

static void i2c_gpio_incomplete_transfer(struct i2c_gpio_private_data *priv,

					u32 pattern, u8 pattern_size)

{

	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;

	int i;



	i2c_lock_adapter(&priv->adap);
@@ -119,8 +113,8 @@ static int fops_incomplete_transfer_set(void *data, u64 addr) 
	setsda(bit_data, 0);

	udelay(bit_data->udelay);



	/* Send ADDR+RD, request ACK, don't send STOP */

	for (i = 8; i >= 0; i--) {

	/* Send pattern, request ACK, don't send STOP */

	for (i = pattern_size - 1; i >= 0; i--) {

		setscl(bit_data, 0);

		udelay(bit_data->udelay / 2);

		setsda(bit_data, (pattern >> i) & 1);
@@ -130,10 +124,24 @@ static int fops_incomplete_transfer_set(void *data, u64 addr) 
	}



	i2c_unlock_adapter(&priv->adap);

}



static int fops_incomplete_addr_phase_set(void *data, u64 addr)

{

	struct i2c_gpio_private_data *priv = data;

	u32 pattern;



	if (addr > 0x7f)

		return -EINVAL;



	/* ADDR (7 bit) + RD (1 bit) + Client ACK, keep SDA hi (1 bit) */

	pattern = (addr << 2) | 3;



	i2c_gpio_incomplete_transfer(priv, pattern, 9);



	return 0;

}

DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_transfer, NULL, fops_incomplete_transfer_set, "%llu\n");

DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n");



static void i2c_gpio_fault_injector_init(struct platform_device *pdev)

{
@@ -156,8 +164,8 @@ static void i2c_gpio_fault_injector_init(struct platform_device *pdev) 


	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);

	debugfs_create_file_unsafe("incomplete_address_phase", 0200, priv->debug_dir,

				   priv, &fops_incomplete_addr_phase);

}



static void i2c_gpio_fault_injector_exit(struct platform_device *pdev)