Re: [PATCH v3 00/26] coresight: Support for ETM system instructions

Mike Leach
2020-10-29T07:56:25Z

Hi Suzuki,

On Wed, 28 Oct 2020 at 22:10, Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
>
> CoreSight ETMv4.4 obsoletes memory mapped access to ETM and
> mandates the system instructions for registers.
> This also implies that they may not be on the amba bus.
> Right now all the CoreSight components are accessed via memory
> map. Also, we have some common routines in coresight generic
> code driver (e.g, CS_LOCK, claim/disclaim), which assume the
> mmio. In order to preserve the generic algorithms at a single
> place and to allow dynamic switch for ETMs, this series introduces
> an abstraction layer for accessing a coresight device. It is
> designed such that the mmio access are fast tracked (i.e, without
> an indirect function call).
>
> This will also help us to get rid of the driver+attribute specific
> sysfs show/store routines and replace them with a single routine
> to access a given register offset (which can be embedded in the
> dev_ext_attribute). This is not currently implemented in the series,
> but can be achieved.
>
> Further we switch the generic routines to work with the abstraction.
> With this in place, we refactor the etm4x code a bit to allow for
> supporting the system instructions with very little new code. The
> changes also switch to using the system instructions by default
> even when we may have an MMIO.
>
> We use TRCDEVARCH for the detection of the ETM component, which
> is a standard register as per CoreSight architecture, rather than
> the etm specific id register TRCIDR1. This is for making sure
> that we are able to detect the ETM via system instructions accurately,
> when the the trace unit could be anything (etm or a custom trace unit).
> To keep the backward compatibility for any existing broken impelementation
> which may not implement TRCDEVARCH, we fall back to TRCIDR1. Also
> this covers us for the changes in the future architecture [0].
>
> The series has been mildly tested on a model for system instructions.
> I would really appreciate any testing on real hardware.
>
> Applies on coresight/next.
>
> [0] https://developer.arm.com/docs/ddi0601/g/aarch64-system-registers/trcidr1
>
> Known issues:
> Checkpatch failure for "coresight: etm4x: Add sysreg access helpers" :
>
> ERROR: Macros with complex values should be enclosed in parentheses
> #121: FILE: drivers/hwtracing/coresight/coresight-etm4x.h:153:
> +#define CASE_READ(res, x) \
> + case (x): { (res) = read_etm4x_sysreg_const_offset((x)); break; }
>
>
> I don't know how to fix that without breaking the build ! Suggestions
> welcome.
>

I hit exactly the same issue with my recent v2 set. The checker really
hates case statements in macros. In my case I shut it up for v3 by
changing:-

#define MAPREG(cval, elem) \
case cval: \
reg->drv_store = &drvcfg->elem; \
break;

if (((offset >= TRCEVENTCTL0R) && (offset <= TRCVIPCSSCTLR)) ||
((offset >= TRCSEQRSTEVR) && (offset <= TRCEXTINSELR)) ||
((offset >= TRCCIDCCTLR0) && (offset <= TRCVMIDCCTLR1))) {
switch (offset) {
/* 32 bit single control and filter registers */
MAPREG(TRCEVENTCTL0R, eventctrl0);
MAPREG(TRCEVENTCTL1R, eventctrl1);
MAPREG(TRCSTALLCTLR, stall_ctrl);
MAPREG(TRCTSCTLR, ts_ctrl);
MAPREG(TRCSYNCPR, syncfreq);
MAPREG(TRCCCCTLR, ccctlr);
MAPREG(TRCBBCTLR, bb_ctrl);
MAPREG(TRCVICTLR, vinst_ctrl);
MAPREG(TRCVIIECTLR, viiectlr);
MAPREG(TRCVISSCTLR, vissctlr);
MAPREG(TRCVIPCSSCTLR, vipcssctlr);
MAPREG(TRCSEQRSTEVR, seq_rst);
MAPREG(TRCSEQSTR, seq_state);
MAPREG(TRCEXTINSELR, ext_inp);
MAPREG(TRCCIDCCTLR0, ctxid_mask0);
MAPREG(TRCCIDCCTLR1, ctxid_mask1);
MAPREG(TRCVMIDCCTLR0, vmid_mask0);
MAPREG(TRCVMIDCCTLR1, vmid_mask1);
default:
err = -EINVAL;
break;
}

to

err = -EINVAL;

#define CHECKREG(cval, elem) \
{ \
if (offset == cval) { \
reg->drv_store = &drvcfg->elem; \
err = 0; \
break; \
} \
}

if (((offset >= TRCEVENTCTL0R) && (offset <= TRCVIPCSSCTLR)) ||
((offset >= TRCSEQRSTEVR) && (offset <= TRCEXTINSELR)) ||
((offset >= TRCCIDCCTLR0) && (offset <= TRCVMIDCCTLR1))) {
do {
CHECKREG(TRCEVENTCTL0R, eventctrl0);
CHECKREG(TRCEVENTCTL1R, eventctrl1);
CHECKREG(TRCSTALLCTLR, stall_ctrl);
CHECKREG(TRCTSCTLR, ts_ctrl);
CHECKREG(TRCSYNCPR, syncfreq);
CHECKREG(TRCCCCTLR, ccctlr);
CHECKREG(TRCBBCTLR, bb_ctrl);
CHECKREG(TRCVICTLR, vinst_ctrl);
CHECKREG(TRCVIIECTLR, viiectlr);
CHECKREG(TRCVISSCTLR, vissctlr);
CHECKREG(TRCVIPCSSCTLR, vipcssctlr);
CHECKREG(TRCSEQRSTEVR, seq_rst);
CHECKREG(TRCSEQSTR, seq_state);
CHECKREG(TRCEXTINSELR, ext_inp);
CHECKREG(TRCCIDCCTLR0, ctxid_mask0);
CHECKREG(TRCCIDCCTLR1, ctxid_mask1);
CHECKREG(TRCVMIDCCTLR0, vmid_mask0);
CHECKREG(TRCVMIDCCTLR1, vmid_mask1);
} while (0);

A bit contrived but functionally the same - and doesn't annoy the
checker, No idea if the code is more or less efficient after
compilation than a standard switch / case combo, but not on a critical
path for me so wasn't bothered.
As I look again I could have actually put the err = -EINVAL; line just
before the while(0) statement - making it more like a case default -
but my current set is too close to release to change that now.

Cheers

Mike

>
> Changes since V2:
> - Several fixes to the ETM register accesses. Access a register
> when it is present.
> - Add support for TRCIDR3.NUMPROCS for v4.2+
> - Drop OS lock detection. Use software lock only in case of mmio.
> - Fix issues with the Exception level masks (Mike Leach)
> - Fall back to using TRCIDR1 when TRCDEVARCH is not "present"
> - Use a generic notion of ETM architecture (rather than using
> the encoding as in registers)
> - Fixed some checkpatch issues.
> - Add support for Self Hosted tracing Arm v8.4 extensions. (Mike
> Leach)
> Originally written by Jonathan, refactored and cleaned up.
> - Changed the dts compatible string to "arm,coresight-etm-sysreg"
> (Mike Leach)
>
> Changes since V1:
> - Flip the switch for iomem from no_iomem to io_mem in csdev_access.
> - Split patches for claim/disclaim and CS_LOCK/UNLOCK conversions.
> - Move device access initialisation for etm4x to the target CPU
> - Cleanup secure exception level mask handling.
> - Switch to use TRCDEVARCH for ETM component discovery. This
> is for making
> - Check the availability of OS/Software Locks before using them.
>
>
> Suzuki K Poulose (26):
> coresight: etm4x: Fix accesses to TRCVMIDCTLR1
> coresight: etm4x: Fix accesses to TRCCIDCTLR1
> coresight: etm4x: Update TRCIDR3.NUMPROCS handling to match v4.2
> coresight: etm4x: Fix accesses to TRCPROCSELR
> coresight: etm4x: Handle TRCVIPCSSCTLR accesses
> coresight: etm4x: Handle access to TRCSSPCICRn
> coresight: Introduce device access abstraction
> coresight: tpiu: Prepare for using coresight device access abstraction
> coresight: Convert coresight_timeout to use access abstraction
> coresight: Convert claim/disclaim operations to use access wrappers
> coresight: etm4x: Always read the registers on the host CPU
> coresight: etm4x: Convert all register accesses
> coresight: etm4x: Add commentary on the registers
> coresight: etm4x: Add sysreg access helpers
> coresight: etm4x: Define DEVARCH register fields
> coresight: etm4x: Check for Software Lock
> coresight: etm4x: Cleanup secure exception level masks
> coresight: etm4x: Clean up exception level masks
> coresight: etm4x: Detect access early on the target CPU
> coresight: etm4x: Handle ETM architecture version
> coresight: etm4x: Use TRCDEVARCH for component discovery
> coresight: etm4x: Add necessary synchronization for sysreg access
> coresight: etm4x: Detect system instructions support
> coresight: etm4x: Refactor probing routine
> coresight: etm4x: Add support for sysreg only devices
> dts: bindings: coresight: ETM system register access only units
>
> .../devicetree/bindings/arm/coresight.txt | 5 +-
> drivers/hwtracing/coresight/coresight-catu.c | 12 +-
> drivers/hwtracing/coresight/coresight-core.c | 130 ++-
> .../hwtracing/coresight/coresight-cti-core.c | 18 +-
> drivers/hwtracing/coresight/coresight-etb10.c | 10 +-
> .../coresight/coresight-etm3x-core.c | 9 +-
> .../coresight/coresight-etm4x-core.c | 758 +++++++++++-------
> .../coresight/coresight-etm4x-sysfs.c | 44 +-
> drivers/hwtracing/coresight/coresight-etm4x.h | 501 +++++++++++-
> .../hwtracing/coresight/coresight-funnel.c | 7 +-
> .../coresight/coresight-replicator.c | 17 +-
> drivers/hwtracing/coresight/coresight-stm.c | 4 +-
> .../hwtracing/coresight/coresight-tmc-core.c | 16 +-
> .../hwtracing/coresight/coresight-tmc-etf.c | 10 +-
> .../hwtracing/coresight/coresight-tmc-etr.c | 4 +-
> drivers/hwtracing/coresight/coresight-tpiu.c | 31 +-
> include/linux/coresight.h | 230 +++++-
> 17 files changed, 1376 insertions(+), 430 deletions(-)
>
> --
> 2.24.1
>

--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK