Hi Wolfram,
On Mon, Sep 14, 2020 at 09:17:37AM +0200, Wolfram Sang wrote:
> Here is an I2C slave backend driver which allows to test some uncommon
> functionalities of the I2C and SMBus world. Usually, you need specific
> devices to test e.g. SMBus Host Notify and such. With this driver you
> just need the slave interface of another I2C controller.
>
> This initial version has testcases for multi-master and SMBus Host
> Notify. Already planned but not yet implemented are SMBus Alert and
> messages with I2C_M_RECV_LEN.
>
> Please read the documentation for further details.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Alain Volmat <alain.volmat@xxxxxx>
> ---
>
> Changes since v1:
> * fixed typo in Kconfig text
> * for READ_BYTES, mask the user supplied address to 7 bits
> (Thanks to Alain for pointing out these two!)
> * removed unneeded of.h-include
>
>
> Documentation/i2c/slave-testunit-backend.rst | 66 +++++++
> drivers/i2c/Kconfig | 8 +
> drivers/i2c/Makefile | 1 +
> drivers/i2c/i2c-slave-testunit.c | 174 +++++++++++++++++++
> 4 files changed, 249 insertions(+)
> create mode 100644 Documentation/i2c/slave-testunit-backend.rst
> create mode 100644 drivers/i2c/i2c-slave-testunit.c
>
> diff --git a/Documentation/i2c/slave-testunit-backend.rst b/Documentation/i2c/slave-testunit-backend.rst
> new file mode 100644
> index 000000000000..f537c62a8a83
> --- /dev/null
> +++ b/Documentation/i2c/slave-testunit-backend.rst
> @@ -0,0 +1,66 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +================================
> +Linux I2C slave testunit backend
> +================================
> +
> +by Wolfram Sang <wsa@xxxxxxxxxxxxxxxxxxxx> in 2020
> +
> +This backend can be used to trigger test cases for I2C bus masters which
> +require a remote device with certain capabilities (and which are usually not so
> +easy to obtain). Examples include multi-master testing, and SMBus Host Notify
> +testing. For some tests, the I2C slave controller must be able to switch
> +between master and slave mode because it needs to send data, too.
> +
> +Note that this is a device for testing and debugging. It should not be enabled
> +in a production build. And while there is some versioning and we try hard to
> +keep backward compatibility, there is no stable ABI guaranteed!
> +
> +Instantiating the device is regular. Example for bus 0, address 0x30:
> +
> +# echo "slave-testunit 0x1030" > /sys/bus/i2c/devices/i2c-0/new_device
> +
> +After that, you will have a write-only device listening. Reads will return an
> +8-bit version number. The device consists of 4 8-bit registers and all must be
> +written to start a testcase, i.e. you must always write 4 bytes to the device.
> +The registers are:
> +
> +0x00 CMD - which test to trigger
> +0x01 DATAL - configuration byte 1 for the test
> +0x02 DATAH - configuration byte 2 for the test
> +0x03 DELAY - delay in n * 10ms until test is started
> +
> +Using 'i2cset' from the i2c-tools package, the generic command looks like:
> +
> +# i2cset -y <bus_num> <testunit_address> <CMD> <DATAL> <DATAH> <DELAY> i
> +
> +DELAY is a generic parameter which will delay the execution of the test in CMD.
> +The commands are described in the following section. An invalid command will
> +result in the transfer not being acknowledged.
> +
> +Commands
> +--------
> +
> +0x00 NOOP (reserved for future use)
> +
> +0x01 READ_BYTES (also needs master mode)
> + DATAL - address to read data from
> + DATAH - number of bytes to read
> +
> +This is useful to test if your bus master driver is handling multi-master
> +correctly. You can trigger the testunit to read bytes from another device on
> +the bus. If the bus master under test also wants to access the bus at the same
> +time, the bus will be busy. Example to read 128 bytes from device 0x50 after
> +50ms of delay:
> +
> +# i2cset -y 0 0x30 0x01 0x50 0x80 0x05 i
> +
> +0x02 SMBUS_HOST_NOTIFY (also needs master mode)
> + DATAL - low byte of the status word to send
> + DATAH - high byte of the status word to send
> +
> +This test will send an SMBUS_HOST_NOTIFY message to the host. Note that the
> +status word is currently ignored in the Linux Kernel. Example to send a
> +notification after 10ms:
> +
> +# i2cset -y 0 0x30 0x02 0x42 0x64 0x01 i
> diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
> index 5449729cdb87..121bf6fc1165 100644
> --- a/drivers/i2c/Kconfig
> +++ b/drivers/i2c/Kconfig
> @@ -125,6 +125,14 @@ config I2C_SLAVE_EEPROM
> This backend makes Linux behave like an I2C EEPROM. Please read
> Documentation/i2c/slave-eeprom-backend.rst for further details.
>
> +config I2C_SLAVE_TESTUNIT
> + tristate "I2C testunit slave driver"
> + help
> + This backend can be used to trigger test cases for I2C bus masters
> + which require a remote device with certain capabilities, e.g.
> + multi-master, SMBus Host Notify, etc. Please read
> + Documentation/i2c/slave-testunit-backend.rst for further details.
> +
> endif
>
> config I2C_DEBUG_CORE
> diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
> index bed6ba63c983..c1d493dc9bac 100644
> --- a/drivers/i2c/Makefile
> +++ b/drivers/i2c/Makefile
> @@ -16,5 +16,6 @@ obj-$(CONFIG_I2C_MUX) += i2c-mux.o
> obj-y += algos/ busses/ muxes/
> obj-$(CONFIG_I2C_STUB) += i2c-stub.o
> obj-$(CONFIG_I2C_SLAVE_EEPROM) += i2c-slave-eeprom.o
> +obj-$(CONFIG_I2C_SLAVE_TESTUNIT) += i2c-slave-testunit.o
>
> ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG
> diff --git a/drivers/i2c/i2c-slave-testunit.c b/drivers/i2c/i2c-slave-testunit.c
> new file mode 100644
> index 000000000000..c4ebb2632c84
> --- /dev/null
> +++ b/drivers/i2c/i2c-slave-testunit.c
> @@ -0,0 +1,174 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * I2C slave mode testunit
> + *
> + * Copyright (C) 2020 by Wolfram Sang, Sang Engineering <wsa@xxxxxxxxxxxxxxxxxxxx>
> + * Copyright (C) 2020 by Renesas Electronics Corporation
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/workqueue.h> /* FIXME: is system_long_wq the best choice? */
> +
> +#define TU_CUR_VERSION 0x01
> +
> +enum testunit_cmds {
> + TU_CMD_READ_BYTES = 1, /* save 0 for ABORT, RESET or similar */
> + TU_CMD_HOST_NOTIFY,
> + TU_NUM_CMDS
> +};
> +
> +enum testunit_regs {
> + TU_REG_CMD,
> + TU_REG_DATAL,
> + TU_REG_DATAH,
> + TU_REG_DELAY,
> + TU_NUM_REGS
> +};
> +
> +enum testunit_flags {
> + TU_FLAG_IN_PROCESS,
> +};
> +
> +struct testunit_data {
> + unsigned long flags;
> + u8 regs[TU_NUM_REGS];
> + u8 reg_idx;
> + struct i2c_client *client;
> + struct delayed_work worker;
> +};
> +
> +static void i2c_slave_testunit_work(struct work_struct *work)
> +{
> + struct testunit_data *tu = container_of(work, struct testunit_data, worker.work);
> + struct i2c_msg msg;
> + u8 msgbuf[256];
> + int ret = 0;
> +
> + msg.addr = I2C_CLIENT_END;
> + msg.buf = msgbuf;
> +
> + switch (tu->regs[TU_REG_CMD]) {
> + case TU_CMD_READ_BYTES:
> + msg.addr = tu->regs[TU_REG_DATAL] & 0x7f;
> + msg.flags = I2C_M_RD;
> + msg.len = tu->regs[TU_REG_DATAH];
> + break;
> +
> + case TU_CMD_HOST_NOTIFY:
> + msg.addr = 0x08;
> + msg.flags = 0;
> + msg.len = 3;
> + msgbuf[0] = tu->client->addr;
> + msgbuf[1] = tu->regs[TU_REG_DATAL];
> + msgbuf[2] = tu->regs[TU_REG_DATAH];
> + break;
> +
> + default:
> + break;
> + }
> +
> + if (msg.addr != I2C_CLIENT_END) {
> + ret = i2c_transfer(tu->client->adapter, &msg, 1);
> + /* convert '0 msgs transferred' to errno */
> + ret = (ret == 0) ? -EIO : ret;
> + }
> +
> + if (ret < 0)
> + dev_err(&tu->client->dev, "CMD%02X failed (%d)\n", tu->regs[TU_REG_CMD], ret);
> +
> + clear_bit(TU_FLAG_IN_PROCESS, &tu->flags);
> +}
> +
> +static int i2c_slave_testunit_slave_cb(struct i2c_client *client,
> + enum i2c_slave_event event, u8 *val)
> +{
> + struct testunit_data *tu = i2c_get_clientdata(client);
> + int ret = 0;
> +
> + switch (event) {
> + case I2C_SLAVE_WRITE_RECEIVED:
> + if (test_bit(TU_FLAG_IN_PROCESS, &tu->flags))
> + return -EBUSY;
> +
> + if (tu->reg_idx < TU_NUM_REGS)
> + tu->regs[tu->reg_idx] = *val;
> + else
> + ret = -EMSGSIZE;
> +
> + if (tu->reg_idx <= TU_NUM_REGS)
> + tu->reg_idx++;
> +
> + /* TU_REG_CMD always written at this point */
> + if (tu->regs[TU_REG_CMD] >= TU_NUM_CMDS)
> + ret = -EINVAL;
> +
> + break;
> +
> + case I2C_SLAVE_STOP:
> + if (tu->reg_idx == TU_NUM_REGS) {
> + set_bit(TU_FLAG_IN_PROCESS, &tu->flags);
> + queue_delayed_work(system_long_wq, &tu->worker,
> + msecs_to_jiffies(10 * tu->regs[TU_REG_DELAY]));
> + }
> + fallthrough;
> +
> + case I2C_SLAVE_WRITE_REQUESTED:
> + tu->reg_idx = 0;
> + break;
> +
> + case I2C_SLAVE_READ_REQUESTED:
> + case I2C_SLAVE_READ_PROCESSED:
> + *val = TU_CUR_VERSION;
> + break;
> + }
> +
> + return ret;
> +}
> +
> +static int i2c_slave_testunit_probe(struct i2c_client *client)
> +{
> + struct testunit_data *tu;
> +
> + tu = devm_kzalloc(&client->dev, sizeof(struct testunit_data), GFP_KERNEL);
> + if (!tu)
> + return -ENOMEM;
> +
> + tu->client = client;
> + i2c_set_clientdata(client, tu);
> + INIT_DELAYED_WORK(&tu->worker, i2c_slave_testunit_work);
> +
> + return i2c_slave_register(client, i2c_slave_testunit_slave_cb);
> +};
> +
> +static int i2c_slave_testunit_remove(struct i2c_client *client)
> +{
> + struct testunit_data *tu = i2c_get_clientdata(client);
> +
> + cancel_delayed_work_sync(&tu->worker);
> + i2c_slave_unregister(client);
> + return 0;
> +}
> +
> +static const struct i2c_device_id i2c_slave_testunit_id[] = {
> + { "slave-testunit", 0 },
> + { }
> +};
> +MODULE_DEVICE_TABLE(i2c, i2c_slave_testunit_id);
> +
> +static struct i2c_driver i2c_slave_testunit_driver = {
> + .driver = {
> + .name = "i2c-slave-testunit",
> + },
> + .probe_new = i2c_slave_testunit_probe,
> + .remove = i2c_slave_testunit_remove,
> + .id_table = i2c_slave_testunit_id,
> +};
> +module_i2c_driver(i2c_slave_testunit_driver);
> +
> +MODULE_AUTHOR("Wolfram Sang <wsa@xxxxxxxxxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("I2C slave mode test unit");
> +MODULE_LICENSE("GPL v2");
> --
> 2.20.1
>
