Re: [PATCH 2/3] coresight: etm4x: Do not save/restore Data trace control registers

On Thu, 11 Apr 2024 at 12:31, Suzuki K Poulose suzuki.poulose@arm.com wrote:

ETM4x doesn't support Data trace on A class CPUs. As such do not access the Data trace control registers during CPU idle. This could cause problems for ETE.

Fixes: f188b5e76aae9 ("coresight: etm4x: Save/restore state across CPU low power states") Reported-by: Yabin Cui yabinc@google.com Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com

---

drivers/hwtracing/coresight/coresight-etm4x-core.c | 6 ------ drivers/hwtracing/coresight/coresight-etm4x.h | 3 --- 2 files changed, 9 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c index fae96151cdaf..ff57aabb24c4 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c @@ -1739,9 +1739,6 @@ static int __etm4_cpu_save(struct etmv4_drvdata *drvdata) state->trcvissctlr = etm4x_read32(csa, TRCVISSCTLR); if (drvdata->nr_pe_cmp) state->trcvipcssctlr = etm4x_read32(csa, TRCVIPCSSCTLR);

•   state->trcvdctlr = etm4x_read32(csa, TRCVDCTLR);
  

•   state->trcvdsacctlr = etm4x_read32(csa, TRCVDSACCTLR);
  

•   state->trcvdarcctlr = etm4x_read32(csa, TRCVDARCCTLR);
  
    for (i = 0; i < drvdata->nrseqstate - 1; i++)
            state->trcseqevr[i] = etm4x_read32(csa, TRCSEQEVRn(i));
  

@@ -1872,9 +1869,6 @@ static void __etm4_cpu_restore(struct etmv4_drvdata *drvdata) etm4x_relaxed_write32(csa, state->trcvissctlr, TRCVISSCTLR); if (drvdata->nr_pe_cmp) etm4x_relaxed_write32(csa, state->trcvipcssctlr, TRCVIPCSSCTLR);

•   etm4x_relaxed_write32(csa, state->trcvdctlr, TRCVDCTLR);
  

•   etm4x_relaxed_write32(csa, state->trcvdsacctlr, TRCVDSACCTLR);
  

•   etm4x_relaxed_write32(csa, state->trcvdarcctlr, TRCVDARCCTLR);
  
    for (i = 0; i < drvdata->nrseqstate - 1; i++)
            etm4x_relaxed_write32(csa, state->trcseqevr[i], TRCSEQEVRn(i));
  

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h index 9ea678bc2e8e..acd2b1db2052 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x.h +++ b/drivers/hwtracing/coresight/coresight-etm4x.h @@ -907,9 +907,6 @@ struct etmv4_save_state { u32 trcviiectlr; u32 trcvissctlr; u32 trcvipcssctlr;

•   u32     trcvdctlr;
  

•   u32     trcvdsacctlr;
  

•   u32     trcvdarcctlr;
  
    u32     trcseqevr[ETM_MAX_SEQ_STATES];
    u32     trcseqrstevr;
  

-- 2.34.1

this change means TRCVDCTLR, TRCVDSACCTLR, TRCVDARCCTLR #defines in ...etm4x.h, along with the CASE_##op.... macros are unused. Could be removed to prevent accidental re-introduction of access to these, perhaps replace with a note saying "we don't need these because...."

Either way

Reviewed-by: Mike Leach mike.leach@linaro.org