11.02.2022 12:11, Akhil R пишет:
>> 10.02.2022 18:36, Akhil R пишет:
>>> Emulate SMBus block read using ContinueXfer to read the length byte
>>>
>>> Signed-off-by: Akhil R <akhilrajeev@xxxxxxxxxx>
>>> ---
>>> drivers/i2c/busses/i2c-tegra.c | 18 ++++++++++++++++--
>>> 1 file changed, 16 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
>>> index 03cea102ab76..2941e42aa6a0 100644
>>> --- a/drivers/i2c/busses/i2c-tegra.c
>>> +++ b/drivers/i2c/busses/i2c-tegra.c
>>> @@ -1233,6 +1233,11 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev
>> *i2c_dev,
>>> return err;
>>>
>>> i2c_dev->msg_buf = msg->buf;
>>> +
>>> + /* The condition true implies smbus block read and len is already read */
>>> + if (msg->flags & I2C_M_RECV_LEN && end_state !=
>> MSG_END_CONTINUE)
>>> + i2c_dev->msg_buf = msg->buf + 1;
>>> +
>>> i2c_dev->msg_buf_remaining = msg->len;
>>> i2c_dev->msg_err = I2C_ERR_NONE;
>>> i2c_dev->msg_read = !!(msg->flags & I2C_M_RD);
>>> @@ -1389,6 +1394,15 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap,
>> struct i2c_msg msgs[],
>>> else
>>> end_type = MSG_END_REPEAT_START;
>>> }
>>> + /* If M_RECV_LEN use ContinueXfer to read the first byte */
>>> + if (msgs[i].flags & I2C_M_RECV_LEN) {
>>> + ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i],
>> MSG_END_CONTINUE);
>>> + if (ret)
>>> + break;
>>> + /* Set the read byte as msg len */
>>> + msgs[i].len = msgs[i].buf[0];
>>> + dev_dbg(i2c_dev->dev, "reading %d bytes\n", msgs[i].len);
>>> + }
>>> ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], end_type);
>>> if (ret)
>>> break;
>>> @@ -1416,10 +1430,10 @@ static u32 tegra_i2c_func(struct i2c_adapter
>> *adap)
>>> {
>>> struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
>>> u32 ret = I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL &
>> ~I2C_FUNC_SMBUS_QUICK) |
>>> - I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
>>> + I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
>>>
>>> if (i2c_dev->hw->has_continue_xfer_support)
>>> - ret |= I2C_FUNC_NOSTART;
>>> + ret |= I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_READ_BLOCK_DATA;
>>>
>>> return ret;
>>> }
>>
>> Please describe how this was tested.
> This is tested using an I2C EEPROM to emulate SMBus block read in which
> we read the first byte as the length of bytes to read. This is an expected
> feature for NVIDIA Grace chipset where there will be an actual SMBus device.
We have several Tegra30+ tablets that have EC on SMBus. Svyatoslav tried
your I2C patch + [1] on Asus TF201 and reported that it breaks EC. Any
idea why it doesn't work?
[1]
https://github.com/grate-driver/linux/commit/aa8d71f5a960ef40503e5448c622d62d1c53a2c0
