[PATCH v3 00/20] coresight: Add support for CPU-wide trace scenarios

[PATCH v3 00/20] coresight: Add support for CPU-wide trace scenarios

[Mathieu Poirier]

This is the third revision of a patchset that adds support for CPU-wide
trace scenarios and as such, it is now possible to issue the following
commands:

        # perf record -e cs_etm/@20070000.etr/ -C 2,3 $COMMAND
        # perf record -e cs_etm/@20070000.etr/ -a $COMMAND

The solution is designed to work for both 1:1 and N:1 source/sink
topologies, though the former hasn't been tested for lack of access to HW.

Most of the changes revolve around allowing more than one event to use
a sink when operated from perf.  More specifically the first event to
use a sink switches it on while the last one is tasked to aggregate traces
and switching off the device.

This is the kernel part of the solution, with the user space portion to be
released in a later set.  All patches (user and kernel) have been rebased
on v5.1-rc3 and are hosted here[1].  Everything has been tested on Juno, the
410c dragonboard, and hikey620 platforms.

Regards,
Mathieu

[1]. https://git.linaro.org/people/mathieu.poirier/coresight.git (5.1-rc3-cpu-wide-v3) 

== Changes for v3 ==
* Added review-by tags (some were dropped due to patch refactoring).
* Split IDR and reference counting patches.
* Moved IDR to struct tmc_drvdata to support 1:1 source/sink topologies.
* Enhanced code comments related to design choices.
* Renamed ETR buffer allocation functions to have a stronger perf semantic.
* Rebased to v5.1-rc3.

== Changes for V2 ==
* Using define ETM4_CFG_BIT_CTXTID rather than hard coded value (Suzuki).
* Moved pid out of struct etr_buf and into struct etr_perf_buffer (Suzuki).
* Removed code related to forcing double buffering (Suzuki).
* Fixed function reallocarray() for older distributions (Mike).
* Fixed counter configuration when dealing with errors(Leo).
* Automatically selecting PID_IN_CONTEXTIDR with ETMv4 driver.
* Rebased to v5.1-rc2.

Mathieu Poirier (20):
  coresight: pmu: Adding ITRACE property to cs_etm PMU
  coresight: etm4x: Add kernel configuration for CONTEXTID
  coresight: etm4x: Skip selector pair 0
  coresight: etm4x: Configure tracers to emit timestamps
  coresight: Adding return code to sink::disable() operation
  coresight: Move reference counting inside sink drivers
  coresight: Properly address errors in sink::disable() functions
  coresight: Properly address concurrency in sink::update() functions
  coresight: perf: Clean up function etm_setup_aux()
  coresight: perf: Refactor function free_event_data()
  coresight: Communicate perf event to sink buffer allocation functions
  coresight: tmc-etr: Refactor function tmc_etr_setup_perf_buf()
  coresight: tmc-etr: Create per-thread buffer allocation function
  coresight: tmc-etr: Introduce the notion of process ID to ETR devices
  coresight: tmc-etr: Introduce the notion of reference counting to ETR
    devices
  coresight: tmc-etr: Introduce the notion of IDR to ETR devices
  coresight: tmc-etr: Allocate and free ETR memory buffers for CPU-wide
    scenarios
  coresight: tmc-etr: Add support for CPU-wide trace scenarios
  coresight: tmc-etf: Add support for CPU-wide trace scenarios
  coresight: etb10: Add support for CPU-wide trace scenarios

 drivers/hwtracing/coresight/Kconfig           |   1 +
 drivers/hwtracing/coresight/coresight-etb10.c |  83 ++++--
 .../hwtracing/coresight/coresight-etm-perf.c  |  37 ++-
 drivers/hwtracing/coresight/coresight-etm4x.c | 113 +++++++-
 .../hwtracing/coresight/coresight-tmc-etf.c   |  82 ++++--
 .../hwtracing/coresight/coresight-tmc-etr.c   | 261 ++++++++++++++++--
 drivers/hwtracing/coresight/coresight-tmc.c   |   6 +
 drivers/hwtracing/coresight/coresight-tmc.h   |  12 +
 drivers/hwtracing/coresight/coresight-tpiu.c  |   9 +-
 drivers/hwtracing/coresight/coresight.c       |  28 +-
 include/linux/coresight-pmu.h                 |   2 +
 include/linux/coresight.h                     |   7 +-
 tools/include/linux/coresight-pmu.h           |   2 +
 13 files changed, 546 insertions(+), 97 deletions(-)

-- 
2.17.1

[PATCH v3 01/20] coresight: pmu: Adding ITRACE property to cs_etm PMU

[Mathieu Poirier]

Add to the capabilities the ITRACE property so that ITRACE START events
are generated when the PMU is switched on by the core.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 4d5a2b9f9d6a..25ae56e924bb 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -566,7 +566,8 @@ static int __init etm_perf_init(void)
 {
 	int ret;
 
-	etm_pmu.capabilities		= PERF_PMU_CAP_EXCLUSIVE;
+	etm_pmu.capabilities		= (PERF_PMU_CAP_EXCLUSIVE |
+					   PERF_PMU_CAP_ITRACE);
 
 	etm_pmu.attr_groups		= etm_pmu_attr_groups;
 	etm_pmu.task_ctx_nr		= perf_sw_context;
-- 
2.17.1

Re: [PATCH v3 01/20] coresight: pmu: Adding ITRACE property to cs_etm PMU

[Suzuki K Poulose]

On 04/04/2019 04:35, Mathieu Poirier wrote:
> Add to the capabilities the ITRACE property so that ITRACE START events
> are generated when the PMU is switched on by the core.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---

Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com>

[PATCH v3 02/20] coresight: etm4x: Add kernel configuration for CONTEXTID

[Mathieu Poirier]

Set the proper bit in the configuration register when contextID tracing
has been requested by user space.  That way PE_CONTEXT elements are
generated by the tracers when a process is installed on a CPU.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/Kconfig              | 1 +
 drivers/hwtracing/coresight/coresight-etm-perf.c | 2 ++
 drivers/hwtracing/coresight/coresight-etm4x.c    | 5 +++++
 include/linux/coresight-pmu.h                    | 2 ++
 tools/include/linux/coresight-pmu.h              | 2 ++
 5 files changed, 12 insertions(+)

diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
index ad34380cac49..44d1650f398e 100644
--- a/drivers/hwtracing/coresight/Kconfig
+++ b/drivers/hwtracing/coresight/Kconfig
@@ -75,6 +75,7 @@ config CORESIGHT_SOURCE_ETM4X
 	bool "CoreSight Embedded Trace Macrocell 4.x driver"
 	depends on ARM64
 	select CORESIGHT_LINKS_AND_SINKS
+	select PID_IN_CONTEXTIDR
 	help
 	  This driver provides support for the ETM4.x tracer module, tracing the
 	  instructions that a processor is executing. This is primarily useful
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 25ae56e924bb..bbfed70b3402 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -29,6 +29,7 @@ static DEFINE_PER_CPU(struct coresight_device *, csdev_src);
 
 /* ETMv3.5/PTM's ETMCR is 'config' */
 PMU_FORMAT_ATTR(cycacc,		"config:" __stringify(ETM_OPT_CYCACC));
+PMU_FORMAT_ATTR(contextid,	"config:" __stringify(ETM_OPT_CTXTID));
 PMU_FORMAT_ATTR(timestamp,	"config:" __stringify(ETM_OPT_TS));
 PMU_FORMAT_ATTR(retstack,	"config:" __stringify(ETM_OPT_RETSTK));
 /* Sink ID - same for all ETMs */
@@ -36,6 +37,7 @@ PMU_FORMAT_ATTR(sinkid,		"config2:0-31");
 
 static struct attribute *etm_config_formats_attr[] = {
 	&format_attr_cycacc.attr,
+	&format_attr_contextid.attr,
 	&format_attr_timestamp.attr,
 	&format_attr_retstack.attr,
 	&format_attr_sinkid.attr,
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index 08ce37c9475d..732ae12fca9b 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -239,6 +239,11 @@ static int etm4_parse_event_config(struct etmv4_drvdata *drvdata,
 	if (attr->config & BIT(ETM_OPT_TS))
 		/* bit[11], Global timestamp tracing bit */
 		config->cfg |= BIT(11);
+
+	if (attr->config & BIT(ETM_OPT_CTXTID))
+		/* bit[6], Context ID tracing bit */
+		config->cfg |= BIT(ETM4_CFG_BIT_CTXTID);
+
 	/* return stack - enable if selected and supported */
 	if ((attr->config & BIT(ETM_OPT_RETSTK)) && drvdata->retstack)
 		/* bit[12], Return stack enable bit */
diff --git a/include/linux/coresight-pmu.h b/include/linux/coresight-pmu.h
index a1a959ba24ff..b0e35eec6499 100644
--- a/include/linux/coresight-pmu.h
+++ b/include/linux/coresight-pmu.h
@@ -12,11 +12,13 @@
 
 /* ETMv3.5/PTM's ETMCR config bit */
 #define ETM_OPT_CYCACC  12
+#define ETM_OPT_CTXTID	14
 #define ETM_OPT_TS      28
 #define ETM_OPT_RETSTK	29
 
 /* ETMv4 CONFIGR programming bits for the ETM OPTs */
 #define ETM4_CFG_BIT_CYCACC	4
+#define ETM4_CFG_BIT_CTXTID	6
 #define ETM4_CFG_BIT_TS		11
 #define ETM4_CFG_BIT_RETSTK	12
 
diff --git a/tools/include/linux/coresight-pmu.h b/tools/include/linux/coresight-pmu.h
index a1a959ba24ff..b0e35eec6499 100644
--- a/tools/include/linux/coresight-pmu.h
+++ b/tools/include/linux/coresight-pmu.h
@@ -12,11 +12,13 @@
 
 /* ETMv3.5/PTM's ETMCR config bit */
 #define ETM_OPT_CYCACC  12
+#define ETM_OPT_CTXTID	14
 #define ETM_OPT_TS      28
 #define ETM_OPT_RETSTK	29
 
 /* ETMv4 CONFIGR programming bits for the ETM OPTs */
 #define ETM4_CFG_BIT_CYCACC	4
+#define ETM4_CFG_BIT_CTXTID	6
 #define ETM4_CFG_BIT_TS		11
 #define ETM4_CFG_BIT_RETSTK	12
 
-- 
2.17.1

Re: [PATCH v3 02/20] coresight: etm4x: Add kernel configuration for CONTEXTID

[Suzuki K Poulose]

On 04/04/2019 04:35, Mathieu Poirier wrote:
> Set the proper bit in the configuration register when contextID tracing
> has been requested by user space.  That way PE_CONTEXT elements are
> generated by the tracers when a process is installed on a CPU.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

[PATCH v3 03/20] coresight: etm4x: Skip selector pair 0

[Mathieu Poirier]

Resource selector pair 0 is always implemented and reserved.  As such
it should not be explicitly programmed.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm4x.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index 732ae12fca9b..d64192c29860 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -138,8 +138,11 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
 			       drvdata->base + TRCCNTVRn(i));
 	}
 
-	/* Resource selector pair 0 is always implemented and reserved */
-	for (i = 0; i < drvdata->nr_resource * 2; i++)
+	/*
+	 * Resource selector pair 0 is always implemented and reserved.  As
+	 * such start at 2.
+	 */
+	for (i = 2; i < drvdata->nr_resource * 2; i++)
 		writel_relaxed(config->res_ctrl[i],
 			       drvdata->base + TRCRSCTLRn(i));
 
-- 
2.17.1

Re: [PATCH v3 03/20] coresight: etm4x: Skip selector pair 0

[Suzuki K Poulose]

On 04/04/2019 04:35, Mathieu Poirier wrote:
> Resource selector pair 0 is always implemented and reserved.  As such
> it should not be explicitly programmed.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

[PATCH v3 04/20] coresight: etm4x: Configure tracers to emit timestamps

[Mathieu Poirier]

Configure timestamps to be emitted at regular intervals in the trace
stream to temporally correlate instructions executed on different CPUs.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm4x.c | 101 +++++++++++++++++-
 1 file changed, 100 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index d64192c29860..46d337fd8442 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -204,6 +204,90 @@ static void etm4_enable_hw_smp_call(void *info)
 	arg->rc = etm4_enable_hw(arg->drvdata);
 }
 
+/*
+ * The goal of function etm4_config_timestamp_event() is to configure a
+ * counter that will tell the tracer to emit a timestamp packet when it
+ * reaches zero.  This is done in order to get a more fine grained idea
+ * of when instructions are executed so that they can be correlated
+ * with execution on other CPUs.
+ *
+ * To do this the counter itself is configured to self reload and
+ * TRCRSCTLR1 (always true) used to get the counter to decrement.  From
+ * there a resource selector is configured with the counter and the
+ * timestamp control register to use the resource selector to trigger the
+ * event that will insert a timestamp packet in the stream.
+ */
+static int etm4_config_timestamp_event(struct etmv4_drvdata *drvdata)
+{
+	int ctridx, ret = -EINVAL;
+	int counter, rselector;
+	u32 val = 0;
+	struct etmv4_config *config = &drvdata->config;
+
+	/* No point in trying if we don't have at least one counter */
+	if (!drvdata->nr_cntr)
+		goto out;
+
+	/* Find a counter that hasn't been initialised */
+	for (ctridx = 0; ctridx < drvdata->nr_cntr; ctridx++)
+		if (config->cntr_val[ctridx] == 0)
+			break;
+
+	/* All the counters have been configured already, bail out */
+	if (ctridx == drvdata->nr_cntr) {
+		pr_debug("%s: no available counter found\n", __func__);
+		ret = -ENOSPC;
+		goto out;
+	}
+
+	/*
+	 * Searching for an available resource selector to use, starting at
+	 * '2' since every implementation has at least 2 resource selector.
+	 * ETMIDR4 gives the number of resource selector _pairs_,
+	 * hence multiply by 2.
+	 */
+	for (rselector = 2; rselector < drvdata->nr_resource * 2; rselector++)
+		if (!config->res_ctrl[rselector])
+			break;
+
+	if (rselector == drvdata->nr_resource * 2) {
+		pr_debug("%s: no available resource selector found\n", __func__);
+		ret = -ENOSPC;
+		goto out;
+	}
+
+	/* Remember what counter we used */
+	counter = 1 << ctridx;
+
+	/*
+	 * Initialise original and reload counter value to the smallest
+	 * possible value in order to get as much precision as we can.
+	 */
+	config->cntr_val[ctridx] = 1;
+	config->cntrldvr[ctridx] = 1;
+
+	/* Set the trace counter control register */
+	val =  0x1 << 16	|  /* Bit 16, reload counter automatically */
+	       0x0 << 7		|  /* Select single resource selector */
+	       0x1;		   /* Resource selector 1, i.e always true */
+
+	config->cntr_ctrl[ctridx] = val;
+
+	val = 0x2 << 16		| /* Group 0b0010 - Counter and sequencers */
+	      counter << 0;	  /* Counter to use */
+
+	config->res_ctrl[rselector] = val;
+
+	val = 0x0 << 7		| /* Select single resource selector */
+	      rselector;	  /* Resource selector */
+
+	config->ts_ctrl = val;
+
+	ret = 0;
+out:
+	return ret;
+}
+
 static int etm4_parse_event_config(struct etmv4_drvdata *drvdata,
 				   struct perf_event *event)
 {
@@ -239,9 +323,24 @@ static int etm4_parse_event_config(struct etmv4_drvdata *drvdata,
 		/* TRM: Must program this for cycacc to work */
 		config->ccctlr = ETM_CYC_THRESHOLD_DEFAULT;
 	}
-	if (attr->config & BIT(ETM_OPT_TS))
+	if (attr->config & BIT(ETM_OPT_TS)) {
+		/*
+		 * Configure timestamps to be emitted at regular intervals in
+		 * order to correlate instructions executed on different CPUs
+		 * (CPU-wide trace scenarios).
+		 */
+		ret = etm4_config_timestamp_event(drvdata);
+
+		/*
+		 * No need to go further if timestamp intervals can't
+		 * be configured.
+		 */
+		if (ret)
+			goto out;
+
 		/* bit[11], Global timestamp tracing bit */
 		config->cfg |= BIT(11);
+	}
 
 	if (attr->config & BIT(ETM_OPT_CTXTID))
 		/* bit[6], Context ID tracing bit */
-- 
2.17.1

Re: [PATCH v3 04/20] coresight: etm4x: Configure tracers to emit timestamps

[Mike Leach]

Hi,

On Thu, 4 Apr 2019 at 04:36, Mathieu Poirier <mathieu.poirier@linaro.org> wrote:
>
> Configure timestamps to be emitted at regular intervals in the trace
> stream to temporally correlate instructions executed on different CPUs.
>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
>  drivers/hwtracing/coresight/coresight-etm4x.c | 101 +++++++++++++++++-
>  1 file changed, 100 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index d64192c29860..46d337fd8442 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> @@ -204,6 +204,90 @@ static void etm4_enable_hw_smp_call(void *info)
>         arg->rc = etm4_enable_hw(arg->drvdata);
>  }
>
> +/*
> + * The goal of function etm4_config_timestamp_event() is to configure a
> + * counter that will tell the tracer to emit a timestamp packet when it
> + * reaches zero.  This is done in order to get a more fine grained idea
> + * of when instructions are executed so that they can be correlated
> + * with execution on other CPUs.
> + *
> + * To do this the counter itself is configured to self reload and
> + * TRCRSCTLR1 (always true) used to get the counter to decrement.  From
> + * there a resource selector is configured with the counter and the
> + * timestamp control register to use the resource selector to trigger the
> + * event that will insert a timestamp packet in the stream.
> + */
> +static int etm4_config_timestamp_event(struct etmv4_drvdata *drvdata)
> +{
> +       int ctridx, ret = -EINVAL;
> +       int counter, rselector;
> +       u32 val = 0;
> +       struct etmv4_config *config = &drvdata->config;
> +
> +       /* No point in trying if we don't have at least one counter */
> +       if (!drvdata->nr_cntr)
> +               goto out;
> +
> +       /* Find a counter that hasn't been initialised */
> +       for (ctridx = 0; ctridx < drvdata->nr_cntr; ctridx++)
> +               if (config->cntr_val[ctridx] == 0)
> +                       break;
> +
> +       /* All the counters have been configured already, bail out */
> +       if (ctridx == drvdata->nr_cntr) {
> +               pr_debug("%s: no available counter found\n", __func__);
> +               ret = -ENOSPC;
> +               goto out;
> +       }
> +
> +       /*
> +        * Searching for an available resource selector to use, starting at
> +        * '2' since every implementation has at least 2 resource selector.
> +        * ETMIDR4 gives the number of resource selector _pairs_,
> +        * hence multiply by 2.
> +        */
> +       for (rselector = 2; rselector < drvdata->nr_resource * 2; rselector++)
> +               if (!config->res_ctrl[rselector])
> +                       break;
> +
> +       if (rselector == drvdata->nr_resource * 2) {
> +               pr_debug("%s: no available resource selector found\n", __func__);
> +               ret = -ENOSPC;
> +               goto out;
> +       }
> +
> +       /* Remember what counter we used */
> +       counter = 1 << ctridx;
> +
> +       /*
> +        * Initialise original and reload counter value to the smallest
> +        * possible value in order to get as much precision as we can.
> +        */
> +       config->cntr_val[ctridx] = 1;
> +       config->cntrldvr[ctridx] = 1;
> +
> +       /* Set the trace counter control register */
> +       val =  0x1 << 16        |  /* Bit 16, reload counter automatically */
> +              0x0 << 7         |  /* Select single resource selector */
> +              0x1;                /* Resource selector 1, i.e always true */
> +
> +       config->cntr_ctrl[ctridx] = val;
> +
> +       val = 0x2 << 16         | /* Group 0b0010 - Counter and sequencers */
> +             counter << 0;       /* Counter to use */
> +
> +       config->res_ctrl[rselector] = val;
> +
> +       val = 0x0 << 7          | /* Select single resource selector */
> +             rselector;          /* Resource selector */
> +
> +       config->ts_ctrl = val;
> +
> +       ret = 0;
> +out:
> +       return ret;
> +}
> +
>  static int etm4_parse_event_config(struct etmv4_drvdata *drvdata,
>                                    struct perf_event *event)
>  {
> @@ -239,9 +323,24 @@ static int etm4_parse_event_config(struct etmv4_drvdata *drvdata,
>                 /* TRM: Must program this for cycacc to work */
>                 config->ccctlr = ETM_CYC_THRESHOLD_DEFAULT;
>         }
> -       if (attr->config & BIT(ETM_OPT_TS))
> +       if (attr->config & BIT(ETM_OPT_TS)) {
> +               /*
> +                * Configure timestamps to be emitted at regular intervals in
> +                * order to correlate instructions executed on different CPUs
> +                * (CPU-wide trace scenarios).
> +                */
> +               ret = etm4_config_timestamp_event(drvdata);
> +
> +               /*
> +                * No need to go further if timestamp intervals can't
> +                * be configured.
> +                */
> +               if (ret)
> +                       goto out;
> +
>                 /* bit[11], Global timestamp tracing bit */
>                 config->cfg |= BIT(11);
> +       }
>

Here you are committing _all_ timestamp usage to be the "hi-freq"
timestamp required for all CPU - wide perf support.
This increases the amount of non-instruction trace - and my not be
desirable in all cases - especially if cycle counts are live as well.
Perhaps define a new ETM_OPT_FREQ_TS which will switch on TS + trigger
counters, and leave ETM_OPT_TS for standard timestamps.

Mike

>         if (attr->config & BIT(ETM_OPT_CTXTID))
>                 /* bit[6], Context ID tracing bit */
> --
> 2.17.1
>
> _______________________________________________
> CoreSight mailing list
> CoreSight@lists.linaro.org
> https://lists.linaro.org/mailman/listinfo/coresight



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

[PATCH v3 05/20] coresight: Adding return code to sink::disable() operation

[Mathieu Poirier]

In preparation to handle device reference counting inside of the sink
drivers, add a return code to the sink::disable() operation so that
proper action can be taken if a sink has not been disabled.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 drivers/hwtracing/coresight/coresight-etb10.c   | 3 ++-
 drivers/hwtracing/coresight/coresight-tmc-etf.c | 5 +++--
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 5 +++--
 drivers/hwtracing/coresight/coresight-tpiu.c    | 3 ++-
 drivers/hwtracing/coresight/coresight.c         | 6 +++++-
 include/linux/coresight.h                       | 2 +-
 6 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 105782ea64c7..71c2a3cdb866 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -325,7 +325,7 @@ static void etb_disable_hw(struct etb_drvdata *drvdata)
 	coresight_disclaim_device(drvdata->base);
 }
 
-static void etb_disable(struct coresight_device *csdev)
+static int etb_disable(struct coresight_device *csdev)
 {
 	struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 	unsigned long flags;
@@ -340,6 +340,7 @@ static void etb_disable(struct coresight_device *csdev)
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	dev_dbg(drvdata->dev, "ETB disabled\n");
+	return 0;
 }
 
 static void *etb_alloc_buffer(struct coresight_device *csdev, int cpu,
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index a5f053f2db2c..d4213e7c2c45 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -273,7 +273,7 @@ static int tmc_enable_etf_sink(struct coresight_device *csdev,
 	return 0;
 }
 
-static void tmc_disable_etf_sink(struct coresight_device *csdev)
+static int tmc_disable_etf_sink(struct coresight_device *csdev)
 {
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
@@ -281,7 +281,7 @@ static void tmc_disable_etf_sink(struct coresight_device *csdev)
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 	if (drvdata->reading) {
 		spin_unlock_irqrestore(&drvdata->spinlock, flags);
-		return;
+		return -EBUSY;
 	}
 
 	/* Disable the TMC only if it needs to */
@@ -293,6 +293,7 @@ static void tmc_disable_etf_sink(struct coresight_device *csdev)
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	dev_dbg(drvdata->dev, "TMC-ETB/ETF disabled\n");
+	return 0;
 }
 
 static int tmc_enable_etf_link(struct coresight_device *csdev,
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index f684283890d3..33501777038a 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1392,7 +1392,7 @@ static int tmc_enable_etr_sink(struct coresight_device *csdev,
 	return -EINVAL;
 }
 
-static void tmc_disable_etr_sink(struct coresight_device *csdev)
+static int tmc_disable_etr_sink(struct coresight_device *csdev)
 {
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
@@ -1400,7 +1400,7 @@ static void tmc_disable_etr_sink(struct coresight_device *csdev)
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 	if (drvdata->reading) {
 		spin_unlock_irqrestore(&drvdata->spinlock, flags);
-		return;
+		return -EBUSY;
 	}
 
 	/* Disable the TMC only if it needs to */
@@ -1412,6 +1412,7 @@ static void tmc_disable_etr_sink(struct coresight_device *csdev)
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	dev_dbg(drvdata->dev, "TMC-ETR disabled\n");
+	return 0;
 }
 
 static const struct coresight_ops_sink tmc_etr_sink_ops = {
diff --git a/drivers/hwtracing/coresight/coresight-tpiu.c b/drivers/hwtracing/coresight/coresight-tpiu.c
index b2f72a1fa402..0d13da1b9df1 100644
--- a/drivers/hwtracing/coresight/coresight-tpiu.c
+++ b/drivers/hwtracing/coresight/coresight-tpiu.c
@@ -94,13 +94,14 @@ static void tpiu_disable_hw(struct tpiu_drvdata *drvdata)
 	CS_LOCK(drvdata->base);
 }
 
-static void tpiu_disable(struct coresight_device *csdev)
+static int tpiu_disable(struct coresight_device *csdev)
 {
 	struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
 	tpiu_disable_hw(drvdata);
 
 	dev_dbg(drvdata->dev, "TPIU disabled\n");
+	return 0;
 }
 
 static const struct coresight_ops_sink tpiu_sink_ops = {
diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index 29cef898afba..13eda4693f81 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -239,9 +239,13 @@ static int coresight_enable_sink(struct coresight_device *csdev,
 
 static void coresight_disable_sink(struct coresight_device *csdev)
 {
+	int ret;
+
 	if (atomic_dec_return(csdev->refcnt) == 0) {
 		if (sink_ops(csdev)->disable) {
-			sink_ops(csdev)->disable(csdev);
+			ret = sink_ops(csdev)->disable(csdev);
+			if (ret)
+				return;
 			csdev->enable = false;
 		}
 	}
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 7b87965f7a65..189cc6ddc92b 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -192,7 +192,7 @@ struct coresight_device {
  */
 struct coresight_ops_sink {
 	int (*enable)(struct coresight_device *csdev, u32 mode, void *data);
-	void (*disable)(struct coresight_device *csdev);
+	int (*disable)(struct coresight_device *csdev);
 	void *(*alloc_buffer)(struct coresight_device *csdev, int cpu,
 			      void **pages, int nr_pages, bool overwrite);
 	void (*free_buffer)(void *config);
-- 
2.17.1

[PATCH v3 06/20] coresight: Move reference counting inside sink drivers

[Mathieu Poirier]

When operating in CPU-wide mode with an N:1 source/sink HW topology,
multiple CPUs can access a sink concurrently.  As such reference counting
needs to happen when the device's spinlock is held to avoid racing with
other operations (start(), update(), stop()), such as:

session A				Session B
-----					-------

enable_sink
atomic_inc(refcount)  = 1

...

atomic_dec(refcount) = 0		enable_sink
if (refcount == 0) disable_sink
					atomic_inc()

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 drivers/hwtracing/coresight/coresight-etb10.c | 21 ++++++++++----
 .../hwtracing/coresight/coresight-tmc-etf.c   | 21 +++++++++++---
 .../hwtracing/coresight/coresight-tmc-etr.c   | 19 +++++++++++--
 drivers/hwtracing/coresight/coresight-tpiu.c  |  6 +++-
 drivers/hwtracing/coresight/coresight.c       | 28 +++++++++----------
 5 files changed, 66 insertions(+), 29 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 71c2a3cdb866..5af50a852e87 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -5,6 +5,7 @@
  * Description: CoreSight Embedded Trace Buffer driver
  */
 
+#include <linux/atomic.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/types.h>
@@ -159,14 +160,15 @@ static int etb_enable_sysfs(struct coresight_device *csdev)
 		goto out;
 	}
 
-	/* Nothing to do, the tracer is already enabled. */
-	if (drvdata->mode == CS_MODE_SYSFS)
-		goto out;
+	if (drvdata->mode == CS_MODE_DISABLED) {
+		ret = etb_enable_hw(drvdata);
+		if (ret)
+			goto out;
 
-	ret = etb_enable_hw(drvdata);
-	if (!ret)
 		drvdata->mode = CS_MODE_SYSFS;
+	}
 
+	atomic_inc(csdev->refcnt);
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 	return ret;
@@ -196,8 +198,10 @@ static int etb_enable_perf(struct coresight_device *csdev, void *data)
 		goto out;
 
 	ret = etb_enable_hw(drvdata);
-	if (!ret)
+	if (!ret) {
 		drvdata->mode = CS_MODE_PERF;
+		atomic_inc(csdev->refcnt);
+	}
 
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -332,6 +336,11 @@ static int etb_disable(struct coresight_device *csdev)
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 
+	if (atomic_dec_return(csdev->refcnt)) {
+		spin_unlock_irqrestore(&drvdata->spinlock, flags);
+		return -EBUSY;
+	}
+
 	/* Disable the ETB only if it needs to */
 	if (drvdata->mode != CS_MODE_DISABLED) {
 		etb_disable_hw(drvdata);
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index d4213e7c2c45..d50a608a60f1 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -4,6 +4,7 @@
  * Author: Mathieu Poirier <mathieu.poirier@linaro.org>
  */
 
+#include <linux/atomic.h>
 #include <linux/circ_buf.h>
 #include <linux/coresight.h>
 #include <linux/perf_event.h>
@@ -180,8 +181,10 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev)
 	 * sink is already enabled no memory is needed and the HW need not be
 	 * touched.
 	 */
-	if (drvdata->mode == CS_MODE_SYSFS)
+	if (drvdata->mode == CS_MODE_SYSFS) {
+		atomic_inc(csdev->refcnt);
 		goto out;
+	}
 
 	/*
 	 * If drvdata::buf isn't NULL, memory was allocated for a previous
@@ -200,11 +203,13 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev)
 	}
 
 	ret = tmc_etb_enable_hw(drvdata);
-	if (!ret)
+	if (!ret) {
 		drvdata->mode = CS_MODE_SYSFS;
-	else
+		atomic_inc(csdev->refcnt);
+	} else {
 		/* Free up the buffer if we failed to enable */
 		used = false;
+	}
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
@@ -239,8 +244,10 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, void *data)
 		if (ret)
 			break;
 		ret  = tmc_etb_enable_hw(drvdata);
-		if (!ret)
+		if (!ret) {
 			drvdata->mode = CS_MODE_PERF;
+			atomic_inc(csdev->refcnt);
+		}
 	} while (0);
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
@@ -279,11 +286,17 @@ static int tmc_disable_etf_sink(struct coresight_device *csdev)
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
+
 	if (drvdata->reading) {
 		spin_unlock_irqrestore(&drvdata->spinlock, flags);
 		return -EBUSY;
 	}
 
+	if (atomic_dec_return(csdev->refcnt)) {
+		spin_unlock_irqrestore(&drvdata->spinlock, flags);
+		return -EBUSY;
+	}
+
 	/* Disable the TMC only if it needs to */
 	if (drvdata->mode != CS_MODE_DISABLED) {
 		tmc_etb_disable_hw(drvdata);
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 33501777038a..f90bca971367 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -4,6 +4,7 @@
  * Author: Mathieu Poirier <mathieu.poirier@linaro.org>
  */
 
+#include <linux/atomic.h>
 #include <linux/coresight.h>
 #include <linux/dma-mapping.h>
 #include <linux/iommu.h>
@@ -1124,8 +1125,10 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev)
 	 * sink is already enabled no memory is needed and the HW need not be
 	 * touched, even if the buffer size has changed.
 	 */
-	if (drvdata->mode == CS_MODE_SYSFS)
+	if (drvdata->mode == CS_MODE_SYSFS) {
+		atomic_inc(csdev->refcnt);
 		goto out;
+	}
 
 	/*
 	 * If we don't have a buffer or it doesn't match the requested size,
@@ -1138,8 +1141,10 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev)
 	}
 
 	ret = tmc_etr_enable_hw(drvdata, drvdata->sysfs_buf);
-	if (!ret)
+	if (!ret) {
 		drvdata->mode = CS_MODE_SYSFS;
+		atomic_inc(csdev->refcnt);
+	}
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
@@ -1370,8 +1375,10 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data)
 	etr_perf->head = PERF_IDX2OFF(handle->head, etr_perf);
 	drvdata->perf_data = etr_perf;
 	rc = tmc_etr_enable_hw(drvdata, etr_perf->etr_buf);
-	if (!rc)
+	if (!rc) {
 		drvdata->mode = CS_MODE_PERF;
+		atomic_inc(csdev->refcnt);
+	}
 
 unlock_out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -1398,11 +1405,17 @@ static int tmc_disable_etr_sink(struct coresight_device *csdev)
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
+
 	if (drvdata->reading) {
 		spin_unlock_irqrestore(&drvdata->spinlock, flags);
 		return -EBUSY;
 	}
 
+	if (atomic_dec_return(csdev->refcnt)) {
+		spin_unlock_irqrestore(&drvdata->spinlock, flags);
+		return -EBUSY;
+	}
+
 	/* Disable the TMC only if it needs to */
 	if (drvdata->mode != CS_MODE_DISABLED) {
 		tmc_etr_disable_hw(drvdata);
diff --git a/drivers/hwtracing/coresight/coresight-tpiu.c b/drivers/hwtracing/coresight/coresight-tpiu.c
index 0d13da1b9df1..7acbeffcc137 100644
--- a/drivers/hwtracing/coresight/coresight-tpiu.c
+++ b/drivers/hwtracing/coresight/coresight-tpiu.c
@@ -5,6 +5,7 @@
  * Description: CoreSight Trace Port Interface Unit driver
  */
 
+#include <linux/atomic.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/device.h>
@@ -73,7 +74,7 @@ static int tpiu_enable(struct coresight_device *csdev, u32 mode, void *__unused)
 	struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
 	tpiu_enable_hw(drvdata);
-
+	atomic_inc(csdev->refcnt);
 	dev_dbg(drvdata->dev, "TPIU enabled\n");
 	return 0;
 }
@@ -98,6 +99,9 @@ static int tpiu_disable(struct coresight_device *csdev)
 {
 	struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
+	if (atomic_dec_return(csdev->refcnt))
+		return -EBUSY;
+
 	tpiu_disable_hw(drvdata);
 
 	dev_dbg(drvdata->dev, "TPIU disabled\n");
diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index 13eda4693f81..19ba121d7451 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -225,14 +225,13 @@ static int coresight_enable_sink(struct coresight_device *csdev,
 	 * We need to make sure the "new" session is compatible with the
 	 * existing "mode" of operation.
 	 */
-	if (sink_ops(csdev)->enable) {
-		ret = sink_ops(csdev)->enable(csdev, mode, data);
-		if (ret)
-			return ret;
-		csdev->enable = true;
-	}
+	if (!sink_ops(csdev)->enable)
+		return -EINVAL;
 
-	atomic_inc(csdev->refcnt);
+	ret = sink_ops(csdev)->enable(csdev, mode, data);
+	if (ret)
+		return ret;
+	csdev->enable = true;
 
 	return 0;
 }
@@ -241,14 +240,13 @@ static void coresight_disable_sink(struct coresight_device *csdev)
 {
 	int ret;
 
-	if (atomic_dec_return(csdev->refcnt) == 0) {
-		if (sink_ops(csdev)->disable) {
-			ret = sink_ops(csdev)->disable(csdev);
-			if (ret)
-				return;
-			csdev->enable = false;
-		}
-	}
+	if (!sink_ops(csdev)->disable)
+		return;
+
+	ret = sink_ops(csdev)->disable(csdev);
+	if (ret)
+		return;
+	csdev->enable = false;
 }
 
 static int coresight_enable_link(struct coresight_device *csdev,
-- 
2.17.1

[PATCH v3 07/20] coresight: Properly address errors in sink::disable() functions

[Mathieu Poirier]

When disabling a sink the reference counter ensures the operation goes
through if nobody else is using it.  As such if drvdata::mode is already
set do CS_MODE_DISABLED, it is an error and should be reported as such.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 drivers/hwtracing/coresight/coresight-etb10.c   | 9 ++++-----
 drivers/hwtracing/coresight/coresight-tmc-etf.c | 9 ++++-----
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 9 ++++-----
 3 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 5af50a852e87..52b7d95ab498 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -341,11 +341,10 @@ static int etb_disable(struct coresight_device *csdev)
 		return -EBUSY;
 	}
 
-	/* Disable the ETB only if it needs to */
-	if (drvdata->mode != CS_MODE_DISABLED) {
-		etb_disable_hw(drvdata);
-		drvdata->mode = CS_MODE_DISABLED;
-	}
+	/* Complain if we (somehow) got out of sync */
+	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
+	etb_disable_hw(drvdata);
+	drvdata->mode = CS_MODE_DISABLED;
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	dev_dbg(drvdata->dev, "ETB disabled\n");
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index d50a608a60f1..30f868676540 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -297,11 +297,10 @@ static int tmc_disable_etf_sink(struct coresight_device *csdev)
 		return -EBUSY;
 	}
 
-	/* Disable the TMC only if it needs to */
-	if (drvdata->mode != CS_MODE_DISABLED) {
-		tmc_etb_disable_hw(drvdata);
-		drvdata->mode = CS_MODE_DISABLED;
-	}
+	/* Complain if we (somehow) got out of sync */
+	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
+	tmc_etb_disable_hw(drvdata);
+	drvdata->mode = CS_MODE_DISABLED;
 
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index f90bca971367..86e748d09dc3 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1416,11 +1416,10 @@ static int tmc_disable_etr_sink(struct coresight_device *csdev)
 		return -EBUSY;
 	}
 
-	/* Disable the TMC only if it needs to */
-	if (drvdata->mode != CS_MODE_DISABLED) {
-		tmc_etr_disable_hw(drvdata);
-		drvdata->mode = CS_MODE_DISABLED;
-	}
+	/* Complain if we (somehow) got out of sync */
+	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
+	tmc_etr_disable_hw(drvdata);
+	drvdata->mode = CS_MODE_DISABLED;
 
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
-- 
2.17.1

[PATCH v3 08/20] coresight: Properly address concurrency in sink::update() functions

[Mathieu Poirier]

When operating in CPU-wide trace scenarios and working with an N:1
source/sink HW topology, update() functions need to be made atomic
in order to avoid racing with start and stop operations.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 drivers/hwtracing/coresight/coresight-etb10.c   | 4 +++-
 drivers/hwtracing/coresight/coresight-tmc-etf.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 52b7d95ab498..6b50e781dc57 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -413,7 +413,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 	const u32 *barrier;
 	u32 read_ptr, write_ptr, capacity;
 	u32 status, read_data;
-	unsigned long offset, to_read;
+	unsigned long offset, to_read, flags;
 	struct cs_buffers *buf = sink_config;
 	struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -422,6 +422,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 
 	capacity = drvdata->buffer_depth * ETB_FRAME_SIZE_WORDS;
 
+	spin_lock_irqsave(&drvdata->spinlock, flags);
 	__etb_disable_hw(drvdata);
 	CS_UNLOCK(drvdata->base);
 
@@ -532,6 +533,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 	}
 	__etb_enable_hw(drvdata);
 	CS_LOCK(drvdata->base);
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	return to_read;
 }
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index 30f868676540..a38ad2b0d95a 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -413,7 +413,7 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
 	u32 *buf_ptr;
 	u64 read_ptr, write_ptr;
 	u32 status;
-	unsigned long offset, to_read;
+	unsigned long offset, to_read, flags;
 	struct cs_buffers *buf = sink_config;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -424,6 +424,7 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
 	if (WARN_ON_ONCE(drvdata->mode != CS_MODE_PERF))
 		return 0;
 
+	spin_lock_irqsave(&drvdata->spinlock, flags);
 	CS_UNLOCK(drvdata->base);
 
 	tmc_flush_and_stop(drvdata);
@@ -517,6 +518,7 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
 		to_read = buf->nr_pages << PAGE_SHIFT;
 	}
 	CS_LOCK(drvdata->base);
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	return to_read;
 }
-- 
2.17.1

[PATCH v3 09/20] coresight: perf: Clean up function etm_setup_aux()

[Mathieu Poirier]

There is no point in allocating sink memory for a trace session if
there is not a way to free it once it is no longer needed.  As such make
sure the sink API function to allocate and free memory have been
implemented before moving ahead with the establishment of a trace
session.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index bbfed70b3402..b8ca3800b56b 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -134,8 +134,7 @@ static void free_event_data(struct work_struct *work)
 	if (event_data->snk_config && !WARN_ON(cpumask_empty(mask))) {
 		cpu = cpumask_first(mask);
 		sink = coresight_get_sink(etm_event_cpu_path(event_data, cpu));
-		if (sink_ops(sink)->free_buffer)
-			sink_ops(sink)->free_buffer(event_data->snk_config);
+		sink_ops(sink)->free_buffer(event_data->snk_config);
 	}
 
 	for_each_cpu(cpu, mask) {
@@ -215,7 +214,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		sink = coresight_get_enabled_sink(true);
 	}
 
-	if (!sink || !sink_ops(sink)->alloc_buffer)
+	if (!sink)
 		goto err;
 
 	mask = &event_data->mask;
@@ -261,6 +260,9 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 	if (cpu >= nr_cpu_ids)
 		goto err;
 
+	if (!sink_ops(sink)->alloc_buffer || !sink_ops(sink)->free_buffer)
+		goto err;
+
 	/* Allocate the sink buffer for this session */
 	event_data->snk_config =
 			sink_ops(sink)->alloc_buffer(sink, cpu, pages,
-- 
2.17.1

[PATCH v3 10/20] coresight: perf: Refactor function free_event_data()

[Mathieu Poirier]

Function free_event_data() is already busy and is bound to become
worse with the addition of CPU-wide trace scenarios.  As such spin
off a new function to strickly take care of the sink buffers.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 .../hwtracing/coresight/coresight-etm-perf.c  | 24 ++++++++++++++-----
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index b8ca3800b56b..806b3dd5872d 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -120,22 +120,34 @@ static int etm_event_init(struct perf_event *event)
 	return ret;
 }
 
+static void free_sink_buffer(struct etm_event_data *event_data)
+{
+	int cpu;
+	cpumask_t *mask = &event_data->mask;
+	struct coresight_device *sink;
+
+	if (WARN_ON(cpumask_empty(mask)))
+		return;
+
+	if (!event_data->snk_config)
+		return;
+
+	cpu = cpumask_first(mask);
+	sink = coresight_get_sink(etm_event_cpu_path(event_data, cpu));
+	sink_ops(sink)->free_buffer(event_data->snk_config);
+}
+
 static void free_event_data(struct work_struct *work)
 {
 	int cpu;
 	cpumask_t *mask;
 	struct etm_event_data *event_data;
-	struct coresight_device *sink;
 
 	event_data = container_of(work, struct etm_event_data, work);
 	mask = &event_data->mask;
 
 	/* Free the sink buffers, if there are any */
-	if (event_data->snk_config && !WARN_ON(cpumask_empty(mask))) {
-		cpu = cpumask_first(mask);
-		sink = coresight_get_sink(etm_event_cpu_path(event_data, cpu));
-		sink_ops(sink)->free_buffer(event_data->snk_config);
-	}
+	free_sink_buffer(event_data);
 
 	for_each_cpu(cpu, mask) {
 		struct list_head **ppath;
-- 
2.17.1

[PATCH v3 11/20] coresight: Communicate perf event to sink buffer allocation functions

[Mathieu Poirier]

Make struct perf_event available to sink buffer allocation functions in
order to use the pid they carry to allocate and free buffer memory along
with regimenting access to what source a sink can collect data for.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etb10.c  |  7 ++++---
 .../hwtracing/coresight/coresight-etm-perf.c   |  2 +-
 .../hwtracing/coresight/coresight-tmc-etf.c    |  7 ++++---
 .../hwtracing/coresight/coresight-tmc-etr.c    | 18 ++++++++++--------
 include/linux/coresight.h                      |  5 +++--
 5 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 6b50e781dc57..7d64c41cd8ac 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -351,10 +351,11 @@ static int etb_disable(struct coresight_device *csdev)
 	return 0;
 }
 
-static void *etb_alloc_buffer(struct coresight_device *csdev, int cpu,
-			      void **pages, int nr_pages, bool overwrite)
+static void *etb_alloc_buffer(struct coresight_device *csdev,
+			      struct perf_event *event, void **pages,
+			      int nr_pages, bool overwrite)
 {
-	int node;
+	int node, cpu = event->cpu;
 	struct cs_buffers *buf;
 
 	if (cpu == -1)
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 806b3dd5872d..3c6294432748 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -277,7 +277,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 
 	/* Allocate the sink buffer for this session */
 	event_data->snk_config =
-			sink_ops(sink)->alloc_buffer(sink, cpu, pages,
+			sink_ops(sink)->alloc_buffer(sink, event, pages,
 						     nr_pages, overwrite);
 	if (!event_data->snk_config)
 		goto err;
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index a38ad2b0d95a..1df1f8fade71 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -350,10 +350,11 @@ static void tmc_disable_etf_link(struct coresight_device *csdev,
 	dev_dbg(drvdata->dev, "TMC-ETF disabled\n");
 }
 
-static void *tmc_alloc_etf_buffer(struct coresight_device *csdev, int cpu,
-				  void **pages, int nr_pages, bool overwrite)
+static void *tmc_alloc_etf_buffer(struct coresight_device *csdev,
+				  struct perf_event *event, void **pages,
+				  int nr_pages, bool overwrite)
 {
-	int node;
+	int node, cpu = event->cpu;
 	struct cs_buffers *buf;
 
 	if (cpu == -1)
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 86e748d09dc3..00db6a6ce23f 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1166,13 +1166,18 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev)
  * reaches a minimum limit (1M), beyond which we give up.
  */
 static struct etr_perf_buffer *
-tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, int node, int nr_pages,
-		       void **pages, bool snapshot)
+tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
+		       int nr_pages, void **pages, bool snapshot)
 {
+	int node, cpu = event->cpu;
 	struct etr_buf *etr_buf;
 	struct etr_perf_buffer *etr_perf;
 	unsigned long size;
 
+	if (cpu == -1)
+		cpu = smp_processor_id();
+	node = cpu_to_node(cpu);
+
 	etr_perf = kzalloc_node(sizeof(*etr_perf), GFP_KERNEL, node);
 	if (!etr_perf)
 		return ERR_PTR(-ENOMEM);
@@ -1210,16 +1215,13 @@ tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, int node, int nr_pages,
 
 
 static void *tmc_alloc_etr_buffer(struct coresight_device *csdev,
-				  int cpu, void **pages, int nr_pages,
-				  bool snapshot)
+				  struct perf_event *event, void **pages,
+				  int nr_pages, bool snapshot)
 {
 	struct etr_perf_buffer *etr_perf;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
-	if (cpu == -1)
-		cpu = smp_processor_id();
-
-	etr_perf = tmc_etr_setup_perf_buf(drvdata, cpu_to_node(cpu),
+	etr_perf = tmc_etr_setup_perf_buf(drvdata, event,
 					  nr_pages, pages, snapshot);
 	if (IS_ERR(etr_perf)) {
 		dev_dbg(drvdata->dev, "Unable to allocate ETR buffer\n");
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 189cc6ddc92b..62a520df8add 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -193,8 +193,9 @@ struct coresight_device {
 struct coresight_ops_sink {
 	int (*enable)(struct coresight_device *csdev, u32 mode, void *data);
 	int (*disable)(struct coresight_device *csdev);
-	void *(*alloc_buffer)(struct coresight_device *csdev, int cpu,
-			      void **pages, int nr_pages, bool overwrite);
+	void *(*alloc_buffer)(struct coresight_device *csdev,
+			      struct perf_event *event, void **pages,
+			      int nr_pages, bool overwrite);
 	void (*free_buffer)(void *config);
 	unsigned long (*update_buffer)(struct coresight_device *csdev,
 			      struct perf_output_handle *handle,
-- 
2.17.1

[PATCH v3 12/20] coresight: tmc-etr: Refactor function tmc_etr_setup_perf_buf()

[Mathieu Poirier]

Refactoring function tmc_etr_setup_perf_buf() so that it only deals
with the high level etr_perf_buffer, leaving the allocation of the
backend buffer (i.e etr_buf) to another function.

That way the backend buffer allocation function can decide if it wants
to reuse an existing buffer (CPU-wide trace scenarios) or simply create
a new one.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 .../hwtracing/coresight/coresight-tmc-etr.c   | 39 ++++++++++++++-----
 1 file changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 00db6a6ce23f..e9c77009188a 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1159,29 +1159,24 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev)
 }
 
 /*
- * tmc_etr_setup_perf_buf: Allocate ETR buffer for use by perf.
+ * alloc_etr_buf: Allocate ETR buffer for use by perf.
  * The size of the hardware buffer is dependent on the size configured
  * via sysfs and the perf ring buffer size. We prefer to allocate the
  * largest possible size, scaling down the size by half until it
  * reaches a minimum limit (1M), beyond which we give up.
  */
-static struct etr_perf_buffer *
-tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
-		       int nr_pages, void **pages, bool snapshot)
+static struct etr_buf *
+alloc_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
+	      int nr_pages, void **pages, bool snapshot)
 {
 	int node, cpu = event->cpu;
 	struct etr_buf *etr_buf;
-	struct etr_perf_buffer *etr_perf;
 	unsigned long size;
 
 	if (cpu == -1)
 		cpu = smp_processor_id();
 	node = cpu_to_node(cpu);
 
-	etr_perf = kzalloc_node(sizeof(*etr_perf), GFP_KERNEL, node);
-	if (!etr_perf)
-		return ERR_PTR(-ENOMEM);
-
 	/*
 	 * Try to match the perf ring buffer size if it is larger
 	 * than the size requested via sysfs.
@@ -1205,6 +1200,32 @@ tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 		size /= 2;
 	} while (size >= TMC_ETR_PERF_MIN_BUF_SIZE);
 
+	return ERR_PTR(-ENOMEM);
+
+done:
+	return etr_buf;
+}
+
+static struct etr_perf_buffer *
+tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
+		       int nr_pages, void **pages, bool snapshot)
+{
+	int node, cpu = event->cpu;
+	struct etr_buf *etr_buf;
+	struct etr_perf_buffer *etr_perf;
+
+	if (cpu == -1)
+		cpu = smp_processor_id();
+	node = cpu_to_node(cpu);
+
+	etr_perf = kzalloc_node(sizeof(*etr_perf), GFP_KERNEL, node);
+	if (!etr_perf)
+		return ERR_PTR(-ENOMEM);
+
+	etr_buf = alloc_etr_buf(drvdata, event, nr_pages, pages, snapshot);
+	if (!IS_ERR(etr_buf))
+		goto done;
+
 	kfree(etr_perf);
 	return ERR_PTR(-ENOMEM);
 
-- 
2.17.1

[PATCH v3 13/20] coresight: tmc-etr: Create per-thread buffer allocation function

[Mathieu Poirier]

Buffer allocation is different when dealing with per-thread and
CPU-wide sessions.  In preparation to support CPU-wide trace scenarios
simplify things by keeping allocation functions for both type separate.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 .../hwtracing/coresight/coresight-tmc-etr.c   | 29 ++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index e9c77009188a..ac1efdfc0d07 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1206,6 +1206,33 @@ alloc_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 	return etr_buf;
 }
 
+static struct etr_buf *
+get_perf_etr_buf_per_thread(struct tmc_drvdata *drvdata,
+			    struct perf_event *event, int nr_pages,
+			    void **pages, bool snapshot)
+{
+	struct etr_buf *etr_buf;
+
+	/*
+	 * In per-thread mode the etr_buf isn't shared, so just go ahead
+	 * with memory allocation.
+	 */
+	etr_buf = alloc_etr_buf(drvdata, event, nr_pages, pages, snapshot);
+
+	return etr_buf;
+}
+
+static struct etr_buf *
+get_perf_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
+		 int nr_pages, void **pages, bool snapshot)
+{
+	if (event->cpu == -1)
+		return get_perf_etr_buf_per_thread(drvdata, event, nr_pages,
+						   pages, snapshot);
+
+	return ERR_PTR(-ENOENT);
+}
+
 static struct etr_perf_buffer *
 tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 		       int nr_pages, void **pages, bool snapshot)
@@ -1222,7 +1249,7 @@ tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 	if (!etr_perf)
 		return ERR_PTR(-ENOMEM);
 
-	etr_buf = alloc_etr_buf(drvdata, event, nr_pages, pages, snapshot);
+	etr_buf = get_perf_etr_buf(drvdata, event, nr_pages, pages, snapshot);
 	if (!IS_ERR(etr_buf))
 		goto done;
 
-- 
2.17.1

[PATCH v3 14/20] coresight: tmc-etr: Introduce the notion of process ID to ETR devices

[Mathieu Poirier]

In preparation to support CPU-wide trace scenarios, introduce the notion
of process ID to ETR devices.  That way events monitoring the same process
can use the same etr_buf, allowing multiple CPUs to use the same sink.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index ac1efdfc0d07..e1774d4bb5f3 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -9,6 +9,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/iommu.h>
 #include <linux/slab.h>
+#include <linux/types.h>
 #include <linux/vmalloc.h>
 #include "coresight-catu.h"
 #include "coresight-etm-perf.h"
@@ -25,6 +26,7 @@ struct etr_flat_buf {
 /*
  * etr_perf_buffer - Perf buffer used for ETR
  * @etr_buf		- Actual buffer used by the ETR
+ * @pid			- The PID this etr_perf_buffer belongs to.
  * @snaphost		- Perf session mode
  * @head		- handle->head at the beginning of the session.
  * @nr_pages		- Number of pages in the ring buffer.
@@ -32,6 +34,7 @@ struct etr_flat_buf {
  */
 struct etr_perf_buffer {
 	struct etr_buf		*etr_buf;
+	pid_t			pid;
 	bool			snapshot;
 	unsigned long		head;
 	int			nr_pages;
@@ -1276,6 +1279,7 @@ static void *tmc_alloc_etr_buffer(struct coresight_device *csdev,
 		return NULL;
 	}
 
+	etr_perf->pid = task_pid_nr(event->owner);
 	etr_perf->snapshot = snapshot;
 	etr_perf->nr_pages = nr_pages;
 	etr_perf->pages = pages;
-- 
2.17.1

[PATCH v3 15/20] coresight: tmc-etr: Introduce the notion of reference counting to ETR devices

[Mathieu Poirier]

This patch adds reference counting to struct etr_buf so that, in CPU-wide
trace scenarios, shared buffers can be disposed of when no longer used.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 5 +++++
 drivers/hwtracing/coresight/coresight-tmc.h     | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index e1774d4bb5f3..1346474ac019 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -8,6 +8,7 @@
 #include <linux/coresight.h>
 #include <linux/dma-mapping.h>
 #include <linux/iommu.h>
+#include <linux/refcount.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/vmalloc.h>
@@ -1221,7 +1222,11 @@ get_perf_etr_buf_per_thread(struct tmc_drvdata *drvdata,
 	 * with memory allocation.
 	 */
 	etr_buf = alloc_etr_buf(drvdata, event, nr_pages, pages, snapshot);
+	if (IS_ERR(etr_buf))
+		goto out;
 
+	refcount_set(&etr_buf->refcount, 1);
+out:
 	return etr_buf;
 }
 
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index 487c53701e9c..ee44906dffe8 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -9,6 +9,7 @@
 
 #include <linux/dma-mapping.h>
 #include <linux/miscdevice.h>
+#include <linux/refcount.h>
 
 #define TMC_RSZ			0x004
 #define TMC_STS			0x00c
@@ -133,6 +134,7 @@ struct etr_buf_operations;
 
 /**
  * struct etr_buf - Details of the buffer used by ETR
+ * refcount	; Number of sources currently using this etr_buf.
  * @mode	: Mode of the ETR buffer, contiguous, Scatter Gather etc.
  * @full	: Trace data overflow
  * @size	: Size of the buffer.
@@ -143,6 +145,7 @@ struct etr_buf_operations;
  * @private	: Backend specific information for the buf
  */
 struct etr_buf {
+	refcount_t			refcount;
 	enum etr_mode			mode;
 	bool				full;
 	ssize_t				size;
-- 
2.17.1

[PATCH v3 16/20] coresight: tmc-etr: Introduce the notion of IDR to ETR devices

[Mathieu Poirier]

In CPU-wide scenarios with an N:1 source/sink topology, sources share
the same sink.  In order to reuse the same sink for all sources an
IDR is needed to archive events that have already been accounted for.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-tmc.c | 4 ++++
 drivers/hwtracing/coresight/coresight-tmc.h | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
index 2a02da3d630f..71c86cffc021 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.c
+++ b/drivers/hwtracing/coresight/coresight-tmc.c
@@ -8,10 +8,12 @@
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/device.h>
+#include <linux/idr.h>
 #include <linux/io.h>
 #include <linux/err.h>
 #include <linux/fs.h>
 #include <linux/miscdevice.h>
+#include <linux/mutex.h>
 #include <linux/property.h>
 #include <linux/uaccess.h>
 #include <linux/slab.h>
@@ -447,6 +449,8 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 					 coresight_get_uci_data(id));
 		if (ret)
 			goto out;
+		idr_init(&drvdata->idr);
+		mutex_init(&drvdata->idr_mutex);
 		break;
 	case TMC_CONFIG_TYPE_ETF:
 		desc.type = CORESIGHT_DEV_TYPE_LINKSINK;
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index ee44906dffe8..c1b1700b2df7 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -8,7 +8,9 @@
 #define _CORESIGHT_TMC_H
 
 #include <linux/dma-mapping.h>
+#include <linux/idr.h>
 #include <linux/miscdevice.h>
+#include <linux/mutex.h>
 #include <linux/refcount.h>
 
 #define TMC_RSZ			0x004
@@ -173,6 +175,8 @@ struct etr_buf {
  * @trigger_cntr: amount of words to store after a trigger.
  * @etr_caps:	Bitmask of capabilities of the TMC ETR, inferred from the
  *		device configuration register (DEVID)
+ * @idr:	Holds etr_bufs allocated for this ETR.
+ * @idr_mutex:	Access serialisation for idr.
  * @perf_data:	PERF buffer for ETR.
  * @sysfs_data:	SYSFS buffer for ETR.
  */
@@ -194,6 +198,8 @@ struct tmc_drvdata {
 	enum tmc_mem_intf_width	memwidth;
 	u32			trigger_cntr;
 	u32			etr_caps;
+	struct idr		idr;
+	struct mutex		idr_mutex;
 	struct etr_buf		*sysfs_buf;
 	void			*perf_data;
 };
-- 
2.17.1

[PATCH v3 17/20] coresight: tmc-etr: Allocate and free ETR memory buffers for CPU-wide scenarios

[Mathieu Poirier]

This patch uses the PID of the process being traced to allocate and free
ETR memory buffers for CPU-wide scenarios.  The implementation is tailored
to handle both N:1 and 1:1 source/sink HW topologies.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 .../hwtracing/coresight/coresight-tmc-etr.c   | 107 +++++++++++++++++-
 1 file changed, 104 insertions(+), 3 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 1346474ac019..61110ef41d00 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -8,6 +8,8 @@
 #include <linux/coresight.h>
 #include <linux/dma-mapping.h>
 #include <linux/iommu.h>
+#include <linux/idr.h>
+#include <linux/mutex.h>
 #include <linux/refcount.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -26,6 +28,7 @@ struct etr_flat_buf {
 
 /*
  * etr_perf_buffer - Perf buffer used for ETR
+ * @drvdata		- The ETR drvdaga this buffer has been allocated for.
  * @etr_buf		- Actual buffer used by the ETR
  * @pid			- The PID this etr_perf_buffer belongs to.
  * @snaphost		- Perf session mode
@@ -34,6 +37,7 @@ struct etr_flat_buf {
  * @pages		- Array of Pages in the ring buffer.
  */
 struct etr_perf_buffer {
+	struct tmc_drvdata	*drvdata;
 	struct etr_buf		*etr_buf;
 	pid_t			pid;
 	bool			snapshot;
@@ -1210,6 +1214,72 @@ alloc_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 	return etr_buf;
 }
 
+static struct etr_buf *
+get_perf_etr_buf_cpu_wide(struct tmc_drvdata *drvdata,
+			  struct perf_event *event, int nr_pages,
+			  void **pages, bool snapshot)
+{
+	int ret;
+	pid_t pid = task_pid_nr(event->owner);
+	struct etr_buf *etr_buf;
+
+retry:
+	/*
+	 * An etr_perf_buffer is associated with an event and holds a reference
+	 * to the AUX ring buffer that was created for that event.  In CPU-wide
+	 * N:1 mode multiple events (one per CPU), each with its own AUX ring
+	 * buffer, share a sink.  As such an etr_perf_buffer is created for each
+	 * event but a single etr_buf associated with the ETR is shared between
+	 * them.  The last event in a trace session will copy the content of the
+	 * etr_buf to its AUX ring buffer.  Ring buffer associated to other
+	 * events are simply not used an freed as events are destoyed.  We still
+	 * need to allocate a ring buffer for each event since we don't know
+	 * which event will be last.
+	 */
+
+	/*
+	 * The first thing to do here is check if an etr_buf has already been
+	 * allocated for this session.  If so it is shared with this event,
+	 * otherwise it is created.
+	 */
+	mutex_lock(&drvdata->idr_mutex);
+	etr_buf = idr_find(&drvdata->idr, pid);
+	if (etr_buf) {
+		refcount_inc(&etr_buf->refcount);
+		mutex_unlock(&drvdata->idr_mutex);
+		return etr_buf;
+	}
+
+	/* If we made it here no buffer has been allocated, do so now. */
+	mutex_unlock(&drvdata->idr_mutex);
+
+	etr_buf = alloc_etr_buf(drvdata, event, nr_pages, pages, snapshot);
+	if (IS_ERR(etr_buf))
+		return etr_buf;
+
+	refcount_set(&etr_buf->refcount, 1);
+
+	/* Now that we have a buffer, add it to the IDR. */
+	mutex_lock(&drvdata->idr_mutex);
+	ret = idr_alloc(&drvdata->idr, etr_buf, pid, pid + 1, GFP_KERNEL);
+	mutex_unlock(&drvdata->idr_mutex);
+
+	/* Another event with this session ID has allocated this buffer. */
+	if (ret == -ENOSPC) {
+		tmc_free_etr_buf(etr_buf);
+		goto retry;
+	}
+
+	/* The IDR can't allocate room for a new session, abandon ship. */
+	if (ret == -ENOMEM) {
+		tmc_free_etr_buf(etr_buf);
+		return ERR_PTR(ret);
+	}
+
+
+	return etr_buf;
+}
+
 static struct etr_buf *
 get_perf_etr_buf_per_thread(struct tmc_drvdata *drvdata,
 			    struct perf_event *event, int nr_pages,
@@ -1238,7 +1308,8 @@ get_perf_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 		return get_perf_etr_buf_per_thread(drvdata, event, nr_pages,
 						   pages, snapshot);
 
-	return ERR_PTR(-ENOENT);
+	return get_perf_etr_buf_cpu_wide(drvdata, event, nr_pages,
+					 pages, snapshot);
 }
 
 static struct etr_perf_buffer *
@@ -1265,7 +1336,13 @@ tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 	return ERR_PTR(-ENOMEM);
 
 done:
+	/*
+	 * Keep a reference to the ETR this buffer has been allocated for
+	 * in order to have access to the IDR in tmc_free_etr_buffer().
+	 */
+	etr_perf->drvdata = drvdata;
 	etr_perf->etr_buf = etr_buf;
+
 	return etr_perf;
 }
 
@@ -1295,9 +1372,33 @@ static void *tmc_alloc_etr_buffer(struct coresight_device *csdev,
 static void tmc_free_etr_buffer(void *config)
 {
 	struct etr_perf_buffer *etr_perf = config;
+	struct tmc_drvdata *drvdata = etr_perf->drvdata;
+	struct etr_buf *buf, *etr_buf = etr_perf->etr_buf;
+
+	if (!etr_buf)
+		goto free_etr_perf_buffer;
+
+	mutex_lock(&drvdata->idr_mutex);
+	/* If we are not the last one to use the buffer, don't touch it. */
+	if (!refcount_dec_and_test(&etr_buf->refcount)) {
+		mutex_unlock(&drvdata->idr_mutex);
+		goto free_etr_perf_buffer;
+	}
+
+	/* We are the last one, remove from the IDR and free the buffer. */
+	buf = idr_remove(&drvdata->idr, etr_perf->pid);
+	mutex_unlock(&drvdata->idr_mutex);
+
+	/*
+	 * Something went very wrong if the buffer associated with this ID
+	 * is not the same in the IDR.  Leak to avoid use after free.
+	 */
+	if (buf && WARN_ON(buf != etr_buf))
+		goto free_etr_perf_buffer;
+
+	tmc_free_etr_buf(etr_perf->etr_buf);
 
-	if (etr_perf->etr_buf)
-		tmc_free_etr_buf(etr_perf->etr_buf);
+free_etr_perf_buffer:
 	kfree(etr_perf);
 }
 
-- 
2.17.1

[PATCH v3 18/20] coresight: tmc-etr: Add support for CPU-wide trace scenarios

[Mathieu Poirier]

This patch adds support for CPU-wide trace scenarios by making sure that
only the sources monitoring the same process have access to a common sink.
Because the sink is shared between sources, the first source to use the
sink switches it on while the last one does the cleanup.  Any attempt to
modify the HW is overlooked for as long as more than one source is using
a sink.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 .../hwtracing/coresight/coresight-tmc-etr.c   | 38 ++++++++++++++++---
 drivers/hwtracing/coresight/coresight-tmc.c   |  2 +
 drivers/hwtracing/coresight/coresight-tmc.h   |  3 ++
 3 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 61110ef41d00..a91c1bc17e2d 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1473,6 +1473,13 @@ tmc_update_etr_buffer(struct coresight_device *csdev,
 	struct etr_buf *etr_buf = etr_perf->etr_buf;
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
+
+	/* Don't do anything if another tracer is using this sink */
+	if (atomic_read(csdev->refcnt) != 1) {
+		spin_unlock_irqrestore(&drvdata->spinlock, flags);
+		goto out;
+	}
+
 	if (WARN_ON(drvdata->perf_data != etr_perf)) {
 		lost = true;
 		spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -1512,17 +1519,15 @@ tmc_update_etr_buffer(struct coresight_device *csdev,
 static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data)
 {
 	int rc = 0;
+	pid_t pid;
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 	struct perf_output_handle *handle = data;
 	struct etr_perf_buffer *etr_perf = etm_perf_sink_config(handle);
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
-	/*
-	 * There can be only one writer per sink in perf mode. If the sink
-	 * is already open in SYSFS mode, we can't use it.
-	 */
-	if (drvdata->mode != CS_MODE_DISABLED || WARN_ON(drvdata->perf_data)) {
+	 /* Don't use this sink if it is already claimed by sysFS */
+	if (drvdata->mode == CS_MODE_SYSFS) {
 		rc = -EBUSY;
 		goto unlock_out;
 	}
@@ -1532,10 +1537,31 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data)
 		goto unlock_out;
 	}
 
+	/* Get a handle on the pid of the process to monitor */
+	pid = etr_perf->pid;
+
+	/* Do not proceed if this device is associated with another session */
+	if (drvdata->pid != -1 && drvdata->pid != pid) {
+		rc = -EBUSY;
+		goto unlock_out;
+	}
+
 	etr_perf->head = PERF_IDX2OFF(handle->head, etr_perf);
 	drvdata->perf_data = etr_perf;
+
+	/*
+	 * No HW configuration is needed if the sink is already in
+	 * use for this session.
+	 */
+	if (drvdata->pid == pid) {
+		atomic_inc(csdev->refcnt);
+		goto unlock_out;
+	}
+
 	rc = tmc_etr_enable_hw(drvdata, etr_perf->etr_buf);
 	if (!rc) {
+		/* Associate with monitored process. */
+		drvdata->pid = pid;
 		drvdata->mode = CS_MODE_PERF;
 		atomic_inc(csdev->refcnt);
 	}
@@ -1579,6 +1605,8 @@ static int tmc_disable_etr_sink(struct coresight_device *csdev)
 	/* Complain if we (somehow) got out of sync */
 	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
 	tmc_etr_disable_hw(drvdata);
+	/* Dissociate from monitored process. */
+	drvdata->pid = -1;
 	drvdata->mode = CS_MODE_DISABLED;
 
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
index 71c86cffc021..fd8267fd8e6b 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.c
+++ b/drivers/hwtracing/coresight/coresight-tmc.c
@@ -417,6 +417,8 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 	devid = readl_relaxed(drvdata->base + CORESIGHT_DEVID);
 	drvdata->config_type = BMVAL(devid, 6, 7);
 	drvdata->memwidth = tmc_get_memwidth(devid);
+	/* This device is not associated with a session */
+	drvdata->pid = -1;
 
 	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
 		if (np)
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index c1b1700b2df7..503f1b3a3741 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -165,6 +165,8 @@ struct etr_buf {
  * @csdev:	component vitals needed by the framework.
  * @miscdev:	specifics to handle "/dev/xyz.tmc" entry.
  * @spinlock:	only one at a time pls.
+ * @pid:	Process ID of the process being monitored by the session
+ *		that is using this component.
  * @buf:	Snapshot of the trace data for ETF/ETB.
  * @etr_buf:	details of buffer used in TMC-ETR
  * @len:	size of the available trace for ETF/ETB.
@@ -186,6 +188,7 @@ struct tmc_drvdata {
 	struct coresight_device	*csdev;
 	struct miscdevice	miscdev;
 	spinlock_t		spinlock;
+	pid_t			pid;
 	bool			reading;
 	union {
 		char		*buf;		/* TMC ETB */
-- 
2.17.1

[PATCH v3 19/20] coresight: tmc-etf: Add support for CPU-wide trace scenarios

[Mathieu Poirier]

This patch adds support for CPU-wide trace scenarios by making sure that
only the sources monitoring the same process have access to a common sink.
Because the sink is shared between sources, the first source to use the
sink switches it on while the last one does the cleanup.  Any attempt to
modify the HW is overlooked for as long as more than one source is using
a sink.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 .../hwtracing/coresight/coresight-tmc-etf.c   | 40 ++++++++++++++++---
 1 file changed, 35 insertions(+), 5 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index 1df1f8fade71..2527b5d3b65e 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -223,6 +223,7 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev)
 static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, void *data)
 {
 	int ret = 0;
+	pid_t pid;
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 	struct perf_output_handle *handle = data;
@@ -233,18 +234,39 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, void *data)
 		if (drvdata->reading)
 			break;
 		/*
-		 * In Perf mode there can be only one writer per sink.  There
-		 * is also no need to continue if the ETB/ETF is already
-		 * operated from sysFS.
+		 * No need to continue if the ETB/ETF is already operated
+		 * from sysFS.
 		 */
-		if (drvdata->mode != CS_MODE_DISABLED)
+		if (drvdata->mode == CS_MODE_SYSFS) {
+			ret = -EBUSY;
 			break;
+		}
+
+		/* Get a handle on the pid of the process to monitor */
+		pid = task_pid_nr(handle->event->owner);
+
+		if (drvdata->pid != -1 && drvdata->pid != pid) {
+			ret = -EBUSY;
+			break;
+		}
 
 		ret = tmc_set_etf_buffer(csdev, handle);
 		if (ret)
 			break;
+
+		/*
+		 * No HW configuration is needed if the sink is already in
+		 * use for this session.
+		 */
+		if (drvdata->pid == pid) {
+			atomic_inc(csdev->refcnt);
+			break;
+		}
+
 		ret  = tmc_etb_enable_hw(drvdata);
 		if (!ret) {
+			/* Associate with monitored process. */
+			drvdata->pid = pid;
 			drvdata->mode = CS_MODE_PERF;
 			atomic_inc(csdev->refcnt);
 		}
@@ -300,6 +322,8 @@ static int tmc_disable_etf_sink(struct coresight_device *csdev)
 	/* Complain if we (somehow) got out of sync */
 	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
 	tmc_etb_disable_hw(drvdata);
+	/* Dissociate from monitored process. */
+	drvdata->pid = -1;
 	drvdata->mode = CS_MODE_DISABLED;
 
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -414,7 +438,7 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
 	u32 *buf_ptr;
 	u64 read_ptr, write_ptr;
 	u32 status;
-	unsigned long offset, to_read, flags;
+	unsigned long offset, to_read = 0, flags;
 	struct cs_buffers *buf = sink_config;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -426,6 +450,11 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
 		return 0;
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
+
+	/* Don't do anything if another tracer is using this sink */
+	if (atomic_read(csdev->refcnt) != 1)
+		goto out;
+
 	CS_UNLOCK(drvdata->base);
 
 	tmc_flush_and_stop(drvdata);
@@ -519,6 +548,7 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
 		to_read = buf->nr_pages << PAGE_SHIFT;
 	}
 	CS_LOCK(drvdata->base);
+out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	return to_read;
-- 
2.17.1

[PATCH v3 20/20] coresight: etb10: Add support for CPU-wide trace scenarios

[Mathieu Poirier]

This patch adds support for CPU-wide trace scenarios by making sure that
only the sources monitoring the same process have access to a common sink.
Because the sink is shared between sources, the first source to use the
sink switches it on while the last one does the cleanup.  Any attempt to
modify the HW is overlooked for as long as more than one source is using
a sink.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etb10.c | 43 +++++++++++++++++--
 1 file changed, 39 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 7d64c41cd8ac..a2379c00d635 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -72,6 +72,8 @@
  * @miscdev:	specifics to handle "/dev/xyz.etb" entry.
  * @spinlock:	only one at a time pls.
  * @reading:	synchronise user space access to etb buffer.
+ * @pid:	Process ID of the process being monitored by the session
+ *		that is using this component.
  * @buf:	area of memory where ETB buffer content gets sent.
  * @mode:	this ETB is being used.
  * @buffer_depth: size of @buf.
@@ -85,6 +87,7 @@ struct etb_drvdata {
 	struct miscdevice	miscdev;
 	spinlock_t		spinlock;
 	local_t			reading;
+	pid_t			pid;
 	u8			*buf;
 	u32			mode;
 	u32			buffer_depth;
@@ -177,28 +180,49 @@ static int etb_enable_sysfs(struct coresight_device *csdev)
 static int etb_enable_perf(struct coresight_device *csdev, void *data)
 {
 	int ret = 0;
+	pid_t pid;
 	unsigned long flags;
 	struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+	struct perf_output_handle *handle = data;
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 
-	/* No need to continue if the component is already in use. */
-	if (drvdata->mode != CS_MODE_DISABLED) {
+	/* No need to continue if the component is already in used by sysFS. */
+	if (drvdata->mode == CS_MODE_SYSFS) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	/* Get a handle on the pid of the process to monitor */
+	pid = task_pid_nr(handle->event->owner);
+
+	if (drvdata->pid != -1 && drvdata->pid != pid) {
 		ret = -EBUSY;
 		goto out;
 	}
 
+	/*
+	 * No HW configuration is needed if the sink is already in
+	 * use for this session.
+	 */
+	if (drvdata->pid == pid) {
+		atomic_inc(csdev->refcnt);
+		goto out;
+	}
+
 	/*
 	 * We don't have an internal state to clean up if we fail to setup
 	 * the perf buffer. So we can perform the step before we turn the
 	 * ETB on and leave without cleaning up.
 	 */
-	ret = etb_set_buffer(csdev, (struct perf_output_handle *)data);
+	ret = etb_set_buffer(csdev, handle);
 	if (ret)
 		goto out;
 
 	ret = etb_enable_hw(drvdata);
 	if (!ret) {
+		/* Associate with monitored process. */
+		drvdata->pid = pid;
 		drvdata->mode = CS_MODE_PERF;
 		atomic_inc(csdev->refcnt);
 	}
@@ -344,6 +368,8 @@ static int etb_disable(struct coresight_device *csdev)
 	/* Complain if we (somehow) got out of sync */
 	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
 	etb_disable_hw(drvdata);
+	/* Dissociate from monitored process. */
+	drvdata->pid = -1;
 	drvdata->mode = CS_MODE_DISABLED;
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
@@ -414,7 +440,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 	const u32 *barrier;
 	u32 read_ptr, write_ptr, capacity;
 	u32 status, read_data;
-	unsigned long offset, to_read, flags;
+	unsigned long offset, to_read = 0, flags;
 	struct cs_buffers *buf = sink_config;
 	struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -424,6 +450,11 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 	capacity = drvdata->buffer_depth * ETB_FRAME_SIZE_WORDS;
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
+
+	/* Don't do anything if another tracer is using this sink */
+	if (atomic_read(csdev->refcnt) != 1)
+		goto out;
+
 	__etb_disable_hw(drvdata);
 	CS_UNLOCK(drvdata->base);
 
@@ -534,6 +565,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 	}
 	__etb_enable_hw(drvdata);
 	CS_LOCK(drvdata->base);
+out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	return to_read;
@@ -742,6 +774,9 @@ static int etb_probe(struct amba_device *adev, const struct amba_id *id)
 	if (!drvdata->buf)
 		return -ENOMEM;
 
+	/* This device is not associated with a session */
+	drvdata->pid = -1;
+
 	desc.type = CORESIGHT_DEV_TYPE_SINK;
 	desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
 	desc.ops = &etb_cs_ops;
-- 
2.17.1