by Mathieu Poirier

[permalink] [raw]

Subject: Re: [PATCH v4 6/6] coresight: etm4x: Support panic kdump

On Fri, Mar 30, 2018 at 11:15:24AM +0800, Leo Yan wrote:
> ETMv4 hardware information and configuration needs to be saved as
> metadata; the metadata format should be compatible with 'perf' tool and
> finally is used by tracing data decoder. ETMv4 works as tracer per CPU,
> we cannot wait for gathering ETM info after CPU panic has happened in
> case there have CPU is locked up and can't response inter-processor
> interrupt for execution dump operations; so it's more reliable to gather
> tracer metadata when all of the CPUs are alive.
>
> This patch saves ETMv4 metadata but with the different method for
> different registers. Since values in TRCIDR{0, 1, 2, 8} and
> TRCAUTHSTATUS are read-only and won't change afterward, thus those
> registers values are filled into metadata structure when tracers are
> instantiated. The configuration and control registers TRCCONFIGR and
> TRCTRACEIDR are dynamically configured, their values are recorded during
> tracer enabling phase.
>
> To avoid unnecessary overload introduced by set/clear operations for
> updating kdump node, we only set ETMv4 metadata info for the
> corresponding kdump node at initialization and won't be cleared anymore.
>
> Suggested-by: Mathieu Poirier <[email protected]>
> Signed-off-by: Leo Yan <[email protected]>
> ---
> drivers/hwtracing/coresight/coresight-etm4x.c | 27 +++++++++++++++++++++++++++
> drivers/hwtracing/coresight/coresight-etm4x.h | 15 +++++++++++++++
> 2 files changed, 42 insertions(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index cf364a5..88b1e19 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> @@ -288,6 +288,8 @@ static int etm4_enable(struct coresight_device *csdev,
> int ret;
> u32 val;
> struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> + struct etmv4_config *config = &drvdata->config;
> + struct etmv4_metadata *metadata = &drvdata->metadata;
>
> val = local_cmpxchg(&drvdata->mode, CS_MODE_DISABLED, mode);
>
> @@ -306,6 +308,10 @@ static int etm4_enable(struct coresight_device *csdev,
> ret = -EINVAL;
> }
>
> + /* Update tracer meta data after tracer configuration */
> + metadata->trcconfigr = config->cfg;
> + metadata->trctraceidr = drvdata->trcid;
> +
> /* The tracer didn't start */
> if (ret)
> local_set(&drvdata->mode, CS_MODE_DISABLED);
> @@ -438,6 +444,7 @@ static void etm4_init_arch_data(void *info)
> u32 etmidr4;
> u32 etmidr5;
> struct etmv4_drvdata *drvdata = info;
> + struct etmv4_metadata *metadata = &drvdata->metadata;
>
> /* Make sure all registers are accessible */
> etm4_os_unlock(drvdata);
> @@ -590,6 +597,16 @@ static void etm4_init_arch_data(void *info)
> drvdata->nrseqstate = BMVAL(etmidr5, 25, 27);
> /* NUMCNTR, bits[30:28] number of counters available for tracing */
> drvdata->nr_cntr = BMVAL(etmidr5, 28, 30);
> +
> + /* Update metadata */
> + metadata->magic = ETM4_METADATA_MAGIC;
> + metadata->cpu = drvdata->cpu;
> + metadata->trcidr0 = readl_relaxed(drvdata->base + TRCIDR0);
> + metadata->trcidr1 = readl_relaxed(drvdata->base + TRCIDR1);
> + metadata->trcidr2 = readl_relaxed(drvdata->base + TRCIDR2);
> + metadata->trcidr8 = readl_relaxed(drvdata->base + TRCIDR8);
> + metadata->trcauthstatus = readl_relaxed(drvdata->base + TRCAUTHSTATUS);
> +
> CS_LOCK(drvdata->base);
> }
>
> @@ -957,6 +974,7 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
> struct device *dev = &adev->dev;
> struct coresight_platform_data *pdata = NULL;
> struct etmv4_drvdata *drvdata;
> + struct etmv4_metadata *metadata;
> struct resource *res = &adev->res;
> struct coresight_desc desc = { 0 };
> struct device_node *np = adev->dev.of_node;
> @@ -1027,6 +1045,15 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
> goto err_arch_supported;
> }
>
> + /* Set source device handler and metadata into kdump node */
> + metadata = &drvdata->metadata;
> + ret = coresight_kdump_source(drvdata->cpu, drvdata->csdev,
> + (char *)metadata, sizeof(*metadata));
> + if (ret) {
> + coresight_unregister(drvdata->csdev);
> + goto err_arch_supported;
> + }
> +
> ret = etm_perf_symlink(drvdata->csdev, true);
> if (ret) {
> coresight_unregister(drvdata->csdev);
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
> index b3b5ea7..08dc8b7 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
> @@ -198,6 +198,20 @@
> #define ETM_EXLEVEL_NS_HYP BIT(14)
> #define ETM_EXLEVEL_NS_NA BIT(15)
>
> +#define ETM4_METADATA_MAGIC 0x4040404040404040ULL

Please dd a comment that this needs to be kept in sync with
__perf_cs_etmv4_magic in tools/perf/util/cs-etm.h.

> +
> +struct etmv4_metadata {
> + u64 magic;
> + u64 cpu;
> + u64 trcconfigr;
> + u64 trctraceidr;
> + u64 trcidr0;
> + u64 trcidr1;
> + u64 trcidr2;
> + u64 trcidr8;
> + u64 trcauthstatus;
> +};
> +
> /**
> * struct etmv4_config - configuration information related to an ETMv4
> * @mode: Controls various modes supported by this ETM.
> @@ -393,6 +407,7 @@ struct etmv4_drvdata {
> bool atbtrig;
> bool lpoverride;
> struct etmv4_config config;
> + struct etmv4_metadata metadata;

Structure documentation please.

> };
>
> /* Address comparator access types */
> --
> 2.7.4
>