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Message-ID: <d3f3d49e-015d-9419-e98b-115c67b258ea@arm.com>
Date: Tue, 19 Jul 2022 22:41:35 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Mike Leach <mike.leach@...aro.org>, coresight@...ts.linaro.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: mathieu.poirier@...aro.org, peterz@...radead.org, mingo@...hat.com,
acme@...nel.org, linux-perf-users@...r.kernel.org,
leo.yan@...aro.org, quic_jinlmao@...cinc.com
Subject: Re: [PATCH v2 04/13] coresight: etm4x: Update ETM4 driver to use
Trace ID API
On 04/07/2022 09:11, Mike Leach wrote:
> The trace ID API is now used to allocate trace IDs for ETM4.x / ETE
> devices.
>
> For perf sessions, these will be allocated on enable, and released on
> disable.
>
> For sysfs sessions, these will be allocated on enable, but only released
> on reset. This allows the sysfs session to interrogate the Trace ID used
> after the session is over - maintaining functional consistency with the
> previous allocation scheme.
>
> The trace ID will also be allocated on read of the mgmt/trctraceid file.
> This ensures that if perf or sysfs read this before enabling trace, the
> value will be the one used for the trace session.
>
> Trace ID initialisation is removed from the _probe() function.
>
> Signed-off-by: Mike Leach <mike.leach@...aro.org>
> ---
> .../coresight/coresight-etm4x-core.c | 65 +++++++++++++++++--
> .../coresight/coresight-etm4x-sysfs.c | 32 ++++++++-
> drivers/hwtracing/coresight/coresight-etm4x.h | 3 +
> 3 files changed, 91 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 87299e99dabb..3f4f7ddd14ec 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -42,6 +42,7 @@
> #include "coresight-etm4x-cfg.h"
> #include "coresight-self-hosted-trace.h"
> #include "coresight-syscfg.h"
> +#include "coresight-trace-id.h"
>
> static int boot_enable;
> module_param(boot_enable, int, 0444);
> @@ -234,6 +235,38 @@ static int etm4_trace_id(struct coresight_device *csdev)
> return drvdata->trcid;
> }
>
> +int etm4_read_alloc_trace_id(struct etmv4_drvdata *drvdata)
> +{
> + int trace_id;
> +
> + /*
> + * This will allocate a trace ID to the cpu,
> + * or return the one currently allocated.
> + */
> + spin_lock(&drvdata->spinlock);
> + trace_id = drvdata->trcid;
> + if (!trace_id) {
> + trace_id = coresight_trace_id_get_cpu_id(drvdata->cpu);
> + if (trace_id > 0)
> + drvdata->trcid = (u8)trace_id;
> + }
> + spin_unlock(&drvdata->spinlock);
> +
> + if (trace_id <= 0)
> + pr_err("Failed to allocate trace ID for %s on CPU%d\n",
> + dev_name(&drvdata->csdev->dev), drvdata->cpu);
dev_err(&drvdata->csdev->dev, ....);
> +
> + return trace_id;
> +}
> +
> +void etm4_release_trace_id(struct etmv4_drvdata *drvdata)
> +{
> + spin_lock(&drvdata->spinlock);
> + coresight_trace_id_put_cpu_id(drvdata->cpu);
> + drvdata->trcid = 0;
> + spin_unlock(&drvdata->spinlock);
> +}
> +
> struct etm4_enable_arg {
> struct etmv4_drvdata *drvdata;
> int rc;
> @@ -715,9 +748,18 @@ static int etm4_enable_perf(struct coresight_device *csdev,
> ret = etm4_parse_event_config(csdev, event);
> if (ret)
> goto out;
> +
> + /* allocate a trace ID */
> + ret = etm4_read_alloc_trace_id(drvdata);
> + if (ret < 0)
> + goto out;
> +
> /* And enable it */
> ret = etm4_enable_hw(drvdata);
>
> + /* failed to enable */
> + if (ret)
> + etm4_release_trace_id(drvdata);
> out:
> return ret;
> }
> @@ -737,6 +779,11 @@ static int etm4_enable_sysfs(struct coresight_device *csdev)
> return ret;
> }
>
> + /* allocate a trace ID */
> + ret = etm4_read_alloc_trace_id(drvdata);
> + if (ret < 0)
> + return ret;
> +
> spin_lock(&drvdata->spinlock);
>
> /*
> @@ -754,6 +801,8 @@ static int etm4_enable_sysfs(struct coresight_device *csdev)
>
> if (!ret)
> dev_dbg(&csdev->dev, "ETM tracing enabled\n");
> + else
> + etm4_release_trace_id(drvdata);
> return ret;
> }
>
> @@ -881,6 +930,9 @@ static int etm4_disable_perf(struct coresight_device *csdev,
> /* TRCVICTLR::SSSTATUS, bit[9] */
> filters->ssstatus = (control & BIT(9));
>
> + /* release trace ID - this may pend release if perf session is still active */
> + etm4_release_trace_id(drvdata);
> +
> return 0;
> }
>
> @@ -906,6 +958,13 @@ static void etm4_disable_sysfs(struct coresight_device *csdev)
> spin_unlock(&drvdata->spinlock);
> cpus_read_unlock();
>
> + /*
> + * unlike for perf session - we only release trace IDs when resetting
> + * sysfs. This permits sysfs users to read the trace ID after the trace
> + * session has completed. This maintains operational behaviour with
> + * prior trace id allocation method
> + */
> +
> dev_dbg(&csdev->dev, "ETM tracing disabled\n");
> }
>
> @@ -1548,11 +1607,6 @@ static int etm4_dying_cpu(unsigned int cpu)
> return 0;
> }
>
> -static void etm4_init_trace_id(struct etmv4_drvdata *drvdata)
> -{
> - drvdata->trcid = coresight_get_trace_id(drvdata->cpu);
> -}
> -
> static int __etm4_cpu_save(struct etmv4_drvdata *drvdata)
> {
> int i, ret = 0;
> @@ -1957,7 +2011,6 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid)
> if (!desc.name)
> return -ENOMEM;
>
> - etm4_init_trace_id(drvdata);
> etm4_set_default(&drvdata->config);
>
> pdata = coresight_get_platform_data(dev);
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> index 6ea8181816fc..c7f896a020d9 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> @@ -266,10 +266,11 @@ static ssize_t reset_store(struct device *dev,
> config->vmid_mask0 = 0x0;
> config->vmid_mask1 = 0x0;
>
> - drvdata->trcid = drvdata->cpu + 1;
> -
> spin_unlock(&drvdata->spinlock);
>
> + /* for sysfs - only release trace id when resetting */
> + etm4_release_trace_id(drvdata);
> +
> cscfg_csdev_reset_feats(to_coresight_device(dev));
>
> return size;
> @@ -2363,6 +2364,31 @@ static struct attribute *coresight_etmv4_attrs[] = {
> NULL,
> };
>
> +/*
> + * Trace ID allocated dynamically on enable - but also allocate on read
> + * in case sysfs or perf read before enable to ensure consistent metadata
> + * information for trace decode
> + */
> +static ssize_t trctraceid_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + int trace_id;
> + struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
> +
> + trace_id = etm4_read_alloc_trace_id(drvdata);
> + if (trace_id < 0)
> + return trace_id;
> +
> + return scnprintf(buf, PAGE_SIZE, "0x%x\n", trace_id);
nit: sysfs_emit(buf, "0x%x\n", trace_id);
> +}
> +
> +/* mgmt group uses extended attributes - no standard macro available */
That doesn't prevent us from using dev_attribute for traceid.
In the end, mgmt group is a collection of "struct attribute *".
All it matters is for the "show" function to decode how to print
the value from the "attribute".
You should be able to use DEVICE_ATTR_RO here ...
> +static struct dev_ext_attribute dev_attr_trctraceid = {
> + __ATTR(trctraceid, 0444, trctraceid_show, NULL),
> + (void *)(unsigned long)TRCTRACEIDR > +};
> +
... and get rid of this. Otherwise looks fine to me.
Suzuki
> struct etmv4_reg {
> struct coresight_device *csdev;
> u32 offset;
> @@ -2499,7 +2525,7 @@ static struct attribute *coresight_etmv4_mgmt_attrs[] = {
> coresight_etm4x_reg(trcpidr3, TRCPIDR3),
> coresight_etm4x_reg(trcoslsr, TRCOSLSR),
> coresight_etm4x_reg(trcconfig, TRCCONFIGR),
> - coresight_etm4x_reg(trctraceid, TRCTRACEIDR),
> + &dev_attr_trctraceid.attr.attr,
> coresight_etm4x_reg(trcdevarch, TRCDEVARCH),
> NULL,
> };
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
> index 33869c1d20c3..e0a9d334375d 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
> @@ -1094,4 +1094,7 @@ static inline bool etm4x_is_ete(struct etmv4_drvdata *drvdata)
> {
> return drvdata->arch >= ETM_ARCH_ETE;
> }
> +
> +int etm4_read_alloc_trace_id(struct etmv4_drvdata *drvdata);
> +void etm4_release_trace_id(struct etmv4_drvdata *drvdata);
> #endif
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