bus speed of /dev/i2c-2 on imx6q

look for IMX_I2C_BIT_RATE in drivers/i2c/busses/i2c-imx.c

how it's set depends a lot on the driver is written and on how new/old the kernel is, for example look at arch/arm/mach-davinci/board-da830-evm.c and you'll find

static struct davinci_i2c_platform_data da830_evm_i2c_0_pdata = {

        .bus_freq       = 100,  /* kHz */

        .bus_delay      = 0,    /* usec */

};

so the speed is set in platform code and the driver takes it from there.

on a newer kernel you may be using devicetree and the i2c speed would be set there rather than platform code. example on BeagleBone Black

in arch/arm/boot/dts/am335x-bone.dts

&i2c1 {

       status = "okay";

       clock-frequency = <400000>;

other drivers may even have a module parameter you can set when you load the module.

In summary, there are many different ways it can be done

Hi selsinork,

in the end the location of interest is here:

https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_3.0.35_4.0.0/arch/arm/mach-mx6/board-mx6_nitrogen6x.c#L434

or for older kernel

https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_3.0.35_1.1.0/arch/arm/mach-mx6/board-mx6_sabrelite.c

I do wonder what is the IMX_I2C_BIT_RATE in drivers/i2c/busses/i2c-imx.c module though.

I am not sure how it relates to the kernel and how it interacts with the aforementioned files .

Thank you

nass sil wrote:

 

I do wonder what is the IMX_I2C_BIT_RATE in drivers/i2c/busses/i2c-imx.c module though.

I am not sure how it relates to the kernel and how it interacts with the aforementioned files .

well it probably depends on exactly which kernel and what patches are applied to know for sure, but if you look at

https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_3.0.35_4.0.0/drivers/i2c/busses/i2c-imx.c

if (pdata && pdata->bitrate)

     i2c_imx_set_clk(i2c_imx, pdata->bitrate);

else

     i2c_imx_set_clk(i2c_imx, IMX_I2C_BIT_RATE);

this essentially means that if you don't specify bitrate in platform data in

https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_3.0.35_4.0.0/arch/arm/mach-mx6/board-mx6_nitrogen6x.c

like so:

static struct imxi2c_platform_data i2c_data = {

     .bitrate = 100000,

};

then you'll get a sensible default as defined by IMX_I2C_BIT_RATE.

Anyway, glad there was enough to point you in the right direction and you found what you were looking for..  Now that you know where its set you should be able to try changing it to see if it helps with your device.

indeed,

i didn't see either file #including the other so I didn't bother looking further down in the file ( i don't know how kernel directory tree is structure either, up until now).

thank you!

hello ,

can you describe pls, how / what is the mechanism  modify it when using module parameter when loading the module.

thank you