[meta-xilinx] PS I2C access by CPU1

[Mike Looijmans]

One would normally add a status="disabled"; instead of changing the compatible.

You can also completely remove the node using:

/delete-node/ &ps7_i2c_0;

I stopped using the PS7 I2C controller, it's just broken and doesn't work 
reliably if you need to transmit more than a few bytes. Use one in logic or 
just bitbang the lines.

As for the clock, it just does not seem right to force-enable all clocks.

I would instantiate a "dummy" platform driver that doesn't really do anything, 
but manages the resources that the FreeRTOS part needs, such as clocks and 
memory ranges. That ensures that other drivers won't access it.


On 14-04-16 18:59, Edward Wingate wrote:
> I'm using Zynq 7020 AMP config with Linux on CPU0 and FreeRTOS on
> CPU1.  ps7_i2c_0 is to be used by CPU1.  What is the proper device
> tree setting to use for ps7_i2c_0 in this case?
>
> 1) ps7_i2c_0: ps7-i2c at e0004000 { compatible = "invalid"; };
> or
> 2) ps7_i2c_0: ps7-i2c at e0004000 {
>          bus-id = <0>;
>          clocks = <&clkc 38>;
>          compatible = "cdns,i2c-r1p10", "xlnx,ps7-i2c-1.00.a";
>          interrupt-parent = <&ps7_scugic_0>;
>          interrupts = <0 25 4>;
>          reg = <0xe0004000 0x1000>;
>          i2c-clk = <400000>;
>          #address-cells = <1>;
>          #size-cells = <0>;    } ;
>
> It seems if I use #1, the i2c port does not respond to CPU1, even
> though I am using "clk_ignore_unused" kernel parameter to ensure i2c
> clock is not disabled.
>
> If I use #2, i2c port responds to CPU1, but then I would need to be
> vigilant that nothing on Linux is trying to use that i2c port?
>
> I am using #2 since #1 doesn't work, but is there a more proper way to
> do this so that Linux/CPU0 doesn't have access to the i2c port?
>
> Thanks for your help.
>
> Ed
>



Kind regards,

Mike Looijmans
System Expert

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