Re: [PATCH 5/6] perf cs-etm: Create ETE decoder

[Leo Yan <leo.yan@linaro.org>]

On Tue, Aug 03, 2021 at 02:09:38PM +0100, James Clark wrote:

[...]

> >> -static enum _ocsd_arch_version cs_etm_decoder__get_arch_ver(u32 reg_idr1)
> >> +static enum _ocsd_arch_version cs_etm_decoder__get_arch_ver(u32 reg_idr1, u32 reg_devarch)
> >>  {
> >> +	/* ETE has to be v9 so set arch version to v8.3+ (ARCH__AA64) */
> >> +	if (cs_etm__is_ete(reg_devarch))
> >> +		return ARCH_AA64;
> >> +
> > 
> > Based on values used in below change, I think we can unify the ETM
> > versio number like:
> > 
> >   ARCH_V8R3 : REVISION, bits[19:16] is 0x3
> >   ARCH_V8R4 : REVISION, bits[19:16] is 0x4
> >   ARCH_V8R5 : REVISION, bits[19:16] is 0x5
> 
> Do you mean make this change in OpenCSD? At the moment it understands these
> values so I'm not sure if the extra ones would be useful:

Yes.  As Mike said, these new macros will cause big changes in OpenCSD,
so I don't have strong opinion to add more macros for tracer versions.

> >> +struct cs_ete_trace_params {
> >> +	struct cs_etmv4_trace_params base_params;
> >> +	u32 reg_devarch;
> > 
> > As we have said, can we directly support ETMv4.5, so that it can
> > smoothly support ETE features?  If so, we don't need to add a new
> > structure "cs_ete_trace_params" at here.
> > 
> 
> I think with the new magic number change this is more likely to stay,
> what are your thoughts?

Agreed.  Just wander if need to define the struct cs_ete_trace_params
as below?

  struct cs_ete_trace_params {
          u32 reg_idr0;
          u32 reg_idr1;
          u32 reg_idr2;
          u32 reg_idr8;
          u32 reg_configr;
          u32 reg_traceidr;
          u32 reg_devarch;
  }

> >> +
> >> +#define TRCDEVARCH_ARCHPART_SHIFT 0
> >> +#define TRCDEVARCH_ARCHPART_MASK  GENMASK(11, 0)
> >> +#define TRCDEVARCH_ARCHPART(x)    (((x) & TRCDEVARCH_ARCHPART_MASK) >> TRCDEVARCH_ARCHPART_SHIFT)
> >> +
> >> +#define TRCDEVARCH_ARCHVER_SHIFT 12
> >> +#define TRCDEVARCH_ARCHVER_MASK  GENMASK(15, 12)
> >> +#define TRCDEVARCH_ARCHVER(x)    (((x) & TRCDEVARCH_ARCHVER_MASK) >> TRCDEVARCH_ARCHVER_SHIFT)
> >> +
> >> +bool cs_etm__is_ete(u32 trcdevarch)
> >> +{
> >> +	/*
> >> +	 * ETE if ARCHVER is 5 (ARCHVER is 4 for ETM) and ARCHPART is 0xA13.
> >> +	 * See ETM_DEVARCH_ETE_ARCH in coresight-etm4x.h
> >> +	 */
> >> +	return TRCDEVARCH_ARCHVER(trcdevarch) == 5 && TRCDEVARCH_ARCHPART(trcdevarch) == 0xA13;
> > 
> > I think this is incorrect.
> > 
> > Here should check the bit field "REVISION, bits[19:16]".  If it's
> > field value is >= 5, then we can say it supports ETE.  I checked the
> > spec for ETMv4.4 and ETMv4.6, both use the same values for the
> > Bits[15:12] = 0x4, so the architecture ID is same for ETMv4.x IPs.
> > 
> 
> I tried to copy this as closely as possible from the ETE driver. See in coresight-etm4x.h
> 
> 	#define ETM_DEVARCH_ETE_ARCH						\
> 		(ETM_DEVARCH_ARCHITECT_ARM | ETM_DEVARCH_ARCHID_ETE | ETM_DEVARCH_PRESENT) 
> 
> Where ETM_DEVARCH_ARCHID_ETE is ARCHVER == 5 and ARCHPART == 0xA13. I didn't check 
> ETM_DEVARCH_ARCHITECT_ARM because I thought that wouldn't be necessary. If we want to make
> the change do detect >= 5 then I think this should be made in the driver first. @Suzuki,
> what do you think?

The tracer has two fields:

- ARCHID bits[15:12]
- REVISION, bits[19:16]

For ETE its ARCHID[15:12] is 0x5 and ETMv4.x's ARCHID[15:12] is 0x4.
So checking ARCHID[15:12] is the right way to distinguish if the
tracer is ETE and creates corresponding decoder for it.

When reviewed this patch I assumed we also need to create ETE decoder
if ETMv4.x has supported packet extension.  As Mike confirmed, all
ETMv4.x tracers keep to use existed way to create decoder; so it's not
necessary to check REVISION bit field.

So please ignore my this comment.

Thanks,
Leo