Re: [PATCH v4 0/6] arm-mpam: Add basic device tree support for resctrl

[Ping Li]

Hi Yin, Rob,

> Changes in v4:
>   - Drop memory controller MSC patch (no concrete platform user).

We do have a concrete platform user for that patch.

On our SoC we have implemented an MPAM 1.1 compliant MSC on the DDR
egress path, which provides system-wide bandwidth QoS. The MSC is
described in the device tree with the "arm,mpam-memory-controller-msc"
and "arm,mpam-msc" compatibles, and this patch is what classifies it
as MPAM_CLASS_MEMORY so that it can be used through resctrl.

We have verified this on hardware with v3 of this series (patches
1-6) on top of a v7.4-rc1 based tree: the memory controller MSC
probes correctly from DT, resctrl exposes the MB resource backed by
it, and both bandwidth allocation (MPAMCFG_MBW_MAX) and the MBWU-based
mbm_total_bytes monitoring work for it.

So this patch is genuinely useful for us, and we would like to ask
you to reconsider dropping it. We are happy to help with testing, or
to provide more details of our DT description if that is useful.

Thanks,
Ping Li