Re: [PATCH v2] dts: arm64: add CoreSight trace support for hi3660

[Suzuki K Poulose]

Hi,

On 04/03/2019 17:18, Mathieu Poirier wrote:
> On Sat, 2 Mar 2019 at 06:00, Leo Yan <leo.yan@xxxxxxxxxx> wrote:
> > On Sat, Mar 02, 2019 at 09:45:22AM +0000, Shiwanglai wrote:
> >
> > [...]
> >
> > > > +           /* Top internals */
> > > > +           funnel@ec031000 {
> > > > +                   compatible = "arm,coresight-funnel", "arm,primecell";
> > > > +                   reg = <0 0xec031000 0 0x1000>;
> > > > +                   clocks = <&crg_ctrl HI3660_PCLK>;
> > > > +                   clock-names = "apb_pclk";
> > > > +
> > > > +                   out-ports {
> > > > +                           port {
> > > > +                                   top_funnel_out: endpoint {
> > > > +                                           remote-endpoint =
> > > > +                                                   <&top_etf_in>;
> > > > +                                   };
> > > > +                           };
> > > > +                   };
> > > > +
> > > > +                   in-ports {
> > > > +                           #address-cells = <1>;
> > > > +                           #size-cells = <0>;
> > > > +
> > > > +                           port@0 {
> > > > +                                   reg = <0>;
> > > > +                                   top_funnel_in0: endpoint {
> > > > +                                           remote-endpoint =
> > > > +                                                   <&cluster0_etf_out>;
> > > > +                                   };
> > > > +                           };
> > > > +
> > > > +                           port@1 {
> > > > +                                   reg = <0>;
> > >
> > > Here should s/<0>/<1>; otherwise DTC will complain warning for mismatching between 'port@1' and 'reg = <0>'.
> >
> > > -- if reg set to 1, then there's no data output from cluster 1 to top.
> >
> > Thanks for the info, Wanglai.  Now I see why write as it is.
> >
> > I can confirm if directly use your patch with perf with mainline
> > kernel I can capture CoreSight trace data successfully on Hikey960
> > board.
> >
> > But since this DT binding will introduce DTC warning, I personally
> > think we can improve for this with below method:
> >
> > We can create a funnel node named "funnel_combo", and we don't need to
> > specify register address range for it; and cluster 0 and cluster 1 will
> > output to "funnel_combo" and "funnel_combo" will output to the top
> > funnel.  Thus the DT binding will write as below.
> >
> > To support for a funnel without any register address range (we have
> > support replicator like this mode), we also need to extend the driver
> > drivers/hwtracing/coresight/coresight-funnel.c.
> >
> > Mathieu, Mike, Suzuki, could you help confirm this is the right
> > direction we should move forward to?
>
> Leo, thanks for testing this out.  Shiwanglai, please add Suzuki and
> myself to future revision of this set - this will help you getting a
> timely response for your work.
>
> As Leo pointed out we already have support for replicators that don't
> have a register map and the same thing should be done in this case.
> But contrary to what was done for replicators, I think we should keep
> the drivers in the same file as Russell did here[1].  That way we can
> keep all things funnel at the same place and reduce the amount of
> kernel configuration options.

I back that. I have already merged the static and programmable replicators
into one and this should be out here soon. So, I back the single driver
approach for funnels.

Cheers
Suzuki


> Regards,
> Mathieu
>
> [1]. https://elixir.bootlin.com/linux/latest/source/drivers/tty/serial/amba-pl011.c#L2819
>
> >