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Date: Tue, 19 Jul 2022 22:45:00 +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 05/13] coresight: etm3x: Update ETM3 driver to use
Trace ID API
On 04/07/2022 09:11, Mike Leach wrote:
> Use the TraceID API to allocate ETM trace IDs dynamically.
>
> As with the etm4x we allocate on enable / disable for perf,
> allocate on enable / reset for sysfs.
>
> Additionally we allocate on sysfs file read as both perf and sysfs
> can read the ID before enabling the hardware.
>
> Remove sysfs option to write trace ID - which is inconsistent with
> both the dynamic allocation method and the fixed allocation method
> previously used.
>
> Signed-off-by: Mike Leach <mike.leach@...aro.org>
> ---
> drivers/hwtracing/coresight/coresight-etm.h | 2 +
> .../coresight/coresight-etm3x-core.c | 68 +++++++++++++++++--
> .../coresight/coresight-etm3x-sysfs.c | 28 +++-----
> 3 files changed, 71 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm.h b/drivers/hwtracing/coresight/coresight-etm.h
> index f3ab96eaf44e..3667428d38b6 100644
> --- a/drivers/hwtracing/coresight/coresight-etm.h
> +++ b/drivers/hwtracing/coresight/coresight-etm.h
> @@ -287,4 +287,6 @@ int etm_get_trace_id(struct etm_drvdata *drvdata);
> void etm_set_default(struct etm_config *config);
> void etm_config_trace_mode(struct etm_config *config);
> struct etm_config *get_etm_config(struct etm_drvdata *drvdata);
> +int etm_read_alloc_trace_id(struct etm_drvdata *drvdata);
> +void etm_release_trace_id(struct etm_drvdata *drvdata);
> #endif
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x-core.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c
> index d0ab9933472b..273f37be322b 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c
> @@ -32,6 +32,7 @@
>
> #include "coresight-etm.h"
> #include "coresight-etm-perf.h"
> +#include "coresight-trace-id.h"
>
> /*
> * Not really modular but using module_param is the easiest way to
> @@ -490,18 +491,61 @@ static int etm_trace_id(struct coresight_device *csdev)
> return etm_get_trace_id(drvdata);
> }
>
> +int etm_read_alloc_trace_id(struct etm_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->traceid;
> + if (!trace_id) {
> + trace_id = coresight_trace_id_get_cpu_id(drvdata->cpu);
> + if (trace_id > 0)
> + drvdata->traceid = (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 etm_release_trace_id(struct etm_drvdata *drvdata)
> +{
> + spin_lock(&drvdata->spinlock);
> + coresight_trace_id_put_cpu_id(drvdata->cpu);
> + drvdata->traceid = 0;
> + spin_unlock(&drvdata->spinlock);
> +}
> +
> static int etm_enable_perf(struct coresight_device *csdev,
> struct perf_event *event)
> {
> struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> + int ret;
>
> if (WARN_ON_ONCE(drvdata->cpu != smp_processor_id()))
> return -EINVAL;
>
> /* Configure the tracer based on the session's specifics */
> etm_parse_event_config(drvdata, event);
> +
> + /* allocate a trace ID */
> + ret = etm_read_alloc_trace_id(drvdata);
> + if (ret < 0)
> + return ret;
> +
> /* And enable it */
> - return etm_enable_hw(drvdata);
> + ret = etm_enable_hw(drvdata);
> +
> + if (ret)
> + etm_release_trace_id(drvdata);
> + return ret;
> }
>
> static int etm_enable_sysfs(struct coresight_device *csdev)
> @@ -510,6 +554,11 @@ static int etm_enable_sysfs(struct coresight_device *csdev)
> struct etm_enable_arg arg = { };
> int ret;
>
> + /* allocate a trace ID */
> + ret = etm_read_alloc_trace_id(drvdata);
> + if (ret < 0)
> + return ret;
> +
> spin_lock(&drvdata->spinlock);
>
> /*
> @@ -532,6 +581,8 @@ static int etm_enable_sysfs(struct coresight_device *csdev)
>
> if (!ret)
> dev_dbg(&csdev->dev, "ETM tracing enabled\n");
> + else
> + etm_release_trace_id(drvdata);
> return ret;
> }
>
> @@ -611,6 +662,8 @@ static void etm_disable_perf(struct coresight_device *csdev)
> coresight_disclaim_device_unlocked(csdev);
>
> CS_LOCK(drvdata->base);
> +
> + etm_release_trace_id(drvdata);
> }
>
> static void etm_disable_sysfs(struct coresight_device *csdev)
> @@ -635,6 +688,13 @@ static void etm_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");
> }
>
> @@ -781,11 +841,6 @@ static void etm_init_arch_data(void *info)
> CS_LOCK(drvdata->base);
> }
>
> -static void etm_init_trace_id(struct etm_drvdata *drvdata)
> -{
> - drvdata->traceid = coresight_get_trace_id(drvdata->cpu);
> -}
> -
> static int __init etm_hp_setup(void)
> {
> int ret;
> @@ -871,7 +926,6 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
> if (etm_arch_supported(drvdata->arch) == false)
> return -EINVAL;
>
> - etm_init_trace_id(drvdata);
> etm_set_default(&drvdata->config);
>
> pdata = coresight_get_platform_data(dev);
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
> index 68fcbf4ce7a8..962d6ac96d64 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
> @@ -86,6 +86,8 @@ static ssize_t reset_store(struct device *dev,
>
> etm_set_default(config);
> spin_unlock(&drvdata->spinlock);
> + /* release trace id outside the spinlock as this fn uses it */
> + etm_release_trace_id(drvdata);
> }
>
> return size;
> @@ -1189,30 +1191,16 @@ static DEVICE_ATTR_RO(cpu);
> static ssize_t traceid_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> - unsigned long val;
> - struct etm_drvdata *drvdata = dev_get_drvdata(dev->parent);
> -
> - val = etm_get_trace_id(drvdata);
> -
> - return sprintf(buf, "%#lx\n", val);
> -}
> -
> -static ssize_t traceid_store(struct device *dev,
> - struct device_attribute *attr,
> - const char *buf, size_t size)
> -{
> - int ret;
> - unsigned long val;
> + int trace_id;
> struct etm_drvdata *drvdata = dev_get_drvdata(dev->parent);
>
> - ret = kstrtoul(buf, 16, &val);
> - if (ret)
> - return ret;
> + trace_id = etm_read_alloc_trace_id(drvdata);
> + if (trace_id < 0)
> + return trace_id;
>
> - drvdata->traceid = val & ETM_TRACEID_MASK;
> - return size;
> + return sprintf(buf, "%#x\n", trace_id);
nit: while at this, please could we switch to sysfs_emit(). Rest looks
fine to me.
Suzuki
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