[PATCH v1 1/1] net: stmmac: dwmac-tegra: Read iommu stream id from device tree

[Andrew Lunn]

> This is not a new dt property, the "iommus" property is an existing property
> that is parsed by the Nvidia implementation of the arm-smmu driver.
> 
> Here is a snippet from the device tree:
> 
> smmu_niso0: iommu at 12000000 {
>         compatible = "nvidia,tegra234-smmu", "nvidia,smmu-500";
> ...
> }
> 
> /* MGBE0 */
> ethernet at 6800000 {
> 	compatible = "nvidia,tegra234-mgbe";
> ...
> 	iommus = <&smmu_niso0 TEGRA234_SID_MGBE>;
> ...
> }
> 
> /* MGBE1 */
> ethernet at 6900000 {
> 	compatible = "nvidia,tegra234-mgbe";
> ...
> 	iommus = <&smmu_niso0 TEGRA234_SID_MGBE_VF1>;
> ...
> }

What i was meaning does the nvidia,tegra234-mgbe binding allow iommus?
I just checked, yes it does.

> If the iommus property is missing completely from the MGBE's device tree node it
> causes secure read/write errors which spam the kernel log and can cause crashes.
> 
> I can add the fallback in V2 with a warning if that is preferred.

The fact it crashed makes me think it is optional. Any existing users
must work, otherwise it would crash, and then be debugged. I guess you
are pushing the usage further, and so have come across this condition.

Is the iommus a SoC property, or a board property? If it is a SoC
property, could you review all the SoC .dtsi files and fix up any
which are missing the property?

Adding a warning is O.K, but ideally the missing property should be
added first.

The merge window is open now, so patches will need to wait two weeks.

	Andrew