Re: [PATCH v5 02/10] dt-bindings: introduce RPMH RSC bindings for Qualcomm SoCs

[Lina Iyer]

On Tue, Apr 10 2018 at 13:36 -0600, Bjorn Andersson wrote:
> On Mon 09 Apr 09:08 PDT 2018, Lina Iyer wrote:
>
> > On Fri, Apr 06 2018 at 19:14 -0600, Stephen Boyd wrote:
> > > Quoting Lina Iyer (2018-04-05 09:18:26)
> > > > diff --git a/Documentation/devicetree/bindings/soc/qcom/rpmh-rsc.txt b/Documentation/devicetree/bindings/soc/qcom/rpmh-rsc.txt
> [..]
> > > > +Example 1:
> > > > +
> > > > +For a TCS whose RSC base address is is 0x179C0000 and is at a DRV id of 2, the
> > > > +register offsets for DRV2 start at 0D00, the register calculations are like
> > > > +this -
> > > > +First tuple: 0x179C0000 + 0x10000 * 2 = 0x179E0000
> > > > +Second tuple: 0x179E0000 + 0xD00 = 0x179E0D00
> > > > +
> > > > +       apps_rsc: rsc@179e000 {
> > > > +               label = "apps_rsc";
> > > > +               compatible = "qcom,rpmh-rsc";
> > > > +               reg = <0x179e0000 0x10000>, <0x179e0d00 0x3000>;
> > >
> > > The first reg property overlaps the second one. Does this second one
> > > ever move around? I would hardcode it in the driver to be 0xd00 away
> > > from the drv base instead of specifying it in DT if it's the same all
> > > the time.
> [..]
> > >
> > The DRV is the voter for an execution environment (Linux, Hypervisor,
> > ATF) in the RSC. The RSC has a lot of other registers that Linux is not
> > privy to. They are access restricted. The memory organization of the RSC
> > mandates that we know the DRV id to access registers specific to the
> > DRV. Unfortunately, not all RSC have identical DRV configuration and the
> > register space is also variable depending on the capability of the RSC.
> > There are functionalities supported by other RSCs in the SoC that are
> > not supported by the RSC associated with the application processor,
> > while not many RSCs' support multiple DRVs. Therefore it doesn't benefit
> > describing the whole RSC as it is not usable from Linux (because of
> > access restrictions).
>
> I generally prefer that we describe the hardware blocks as accurate as
> possible, instead of applying current restrictions on Linux onto the
> description. This ensures that we can reuse the binding and drivers in
> configurations not considered today. However, afaict we still have the
> problem that we need a way to express where in the RSC our TCS sits.
>
> Regardless of what's right or not, the given example causes the driver
> to fail probing, so something needs to be changed.
I have been using this in DT and I haven't seen failures. Could you send
me the logs?

Thanks,
Lina

> (Making the drv size
> 0xd00 is functional but doesn't really relate to any bondary in the
> register space).
>
> Regards,
> Bjorn