10Kz I2c speed.

[edpil02]

I just bought a RX4070 Super Ti.
Unfortunately the funny manufacturer put on the i2c bus a controller
that runs at 10kz instead of the standard 100kz , so reading and writing always fails.
I know that nvapi can change the bus speed but the necessary function is not in libnvidia-api.
Is there another way to manage the i2c bus speed for a driver.
Thanks.

[aritger]

I don't have experience with it, but if you want to hack on the nvidia.ko source, it looks like you could specify the speed in NV402C_CTRL_I2C_TRANSACTION_PARAMS::flags field in src/nvidia/arch/nvalloc/unix/src/osapi.c:RmNonDPAuxI2CTransfer().

I think add a line like:

params->flags = DRF_DEF(402C_CTRL, _I2C_FLAGS, _SPEED_MODE, _10KHZ);

or:

params->flags = DRF_DEF(402C_CTRL, _I2C_FLAGS, _SPEED_MODE, _DEFAULT);

The speeds are defined in src/common/sdk/nvidia/inc/ctrl/ctrl402c.h.
Annoyingly, the zero value is not _DEFAULT, but _100KHZ:

#define NV402C_CTRL_I2C_FLAGS_SPEED_MODE_100KHZ                                 (0x00000000)
#define NV402C_CTRL_I2C_FLAGS_SPEED_MODE_200KHZ                                 (0x00000001)
#define NV402C_CTRL_I2C_FLAGS_SPEED_MODE_400KHZ                                 (0x00000002)
#define NV402C_CTRL_I2C_FLAGS_SPEED_MODE_33KHZ                                  (0x00000003)
#define NV402C_CTRL_I2C_FLAGS_SPEED_MODE_10KHZ                                  (0x00000004)
#define NV402C_CTRL_I2C_FLAGS_SPEED_MODE_3KHZ                                   (0x00000005)
#define NV402C_CTRL_I2C_FLAGS_SPEED_MODE_DEFAULT                                (0x00000006)
#define NV402C_CTRL_I2C_FLAGS_SPEED_MODE_300KHZ                                 (0x00000007)

It is probably a bug that the driver doesn't use DEFAULT today.

Let me know if that helps.

[edpil02]

After several attempts your solution works.
The device is finally on the right bus and the right address.

Thank you very much.

[aritger]

Thanks for the update. What was ultimately the change you made that worked for you? I'd like to make sure the NVIDIA driver code gets updated with a fix. I imagine

params->flags = DRF_DEF(402C_CTRL, _I2C_FLAGS, _SPEED_MODE, _DEFAULT);

would be the most generally applicable.

[edpil02]

It's not that simple because i have two oem devices on the i2c bus , one in bus 4 (10khz) and another in bus 5 (100khz).
With params->flags = DRF_DEF(402C_CTRL, _I2C_FLAGS, _SPEED_MODE, _DEFAULT); no device is detected except DPAuxI2C.
So I used params->flags = DRF_DEF(402C_CTRL, _I2C_FLAGS, _SPEED_MODE, _10KHZ ) ; but if bus 4 (10kz) is detected bus 5 is not (speed too slow) .
The ideal would be to be able to choose the bus speed when reading or writing as NvAPI_I2CRead* does in windows .

[edpil02]

I finally did a dirty hard-coded hack to change the bus speeds.

if (addr == 0x4a) // 10KHZ addr
{
params->flags = DRF_DEF(402C_CTRL, _I2C_FLAGS, _SPEED_MODE, _10KHZ);
}
else
{
params->flags = DRF_DEF(402C_CTRL, _I2C_FLAGS, _SPEED_MODE, _100KHZ);
}

[aritger]

I'm glad you got it working. Out of curiosity, who was the OEM of your RX4070 Super Ti? I'd like to try to replicate the problem. Thanks.

[edpil02]

I was trying to help a developer of the OpenRGB project for ZOTAC GAMING GeForce RTX 4070 Ti SUPER Trinity * cards on Linux.
He found that the detection problem was due to the slow i2c controller. Title : "Zotac GPUs with slow RGB controller at 0x4A".

On windows he solved the problem with struct ( NVAPI_I2C_INFO )
{
// set the bus parameters needed to talk to this controller
nvbus->is_ddc_port = 1;
nvbus->display_mask = 1;
nvbus->i2c_speed_khz = NV_I2C_SPEED::NVAPI_I2C_SPEED_10KHZ;
}

But for Linux we still don't have an elegant solution because NvAPI_I2CRead * Write are not implemented in libnvidia-api.
On the other hand the rgb functions NvAPI_GPU_SetIllumination* are but it is for other rgb controllers.

Thanks again for your help.