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From: James Clark <james.clark@arm.com>
To: suzuki.poulose@arm.com, mathieu.poirier@linaro.org,
	coresight@lists.linaro.org, leo.yan@linaro.com,
	mike.leach@linaro.org
Cc: James Clark <james.clark@arm.com>, Leo Yan <leo.yan@linaro.org>,
	John Garry <john.garry@huawei.com>, Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: [PATCH v2 6/6] Documentation: coresight: Expand branch broadcast documentation
Date: Thu, 13 Jan 2022 09:10:55 +0000	[thread overview]
Message-ID: <20220113091056.1297982-7-james.clark@arm.com> (raw)
In-Reply-To: <20220113091056.1297982-1-james.clark@arm.com>

Now that there is a way of enabling branch broadcast via perf, mention
the possible use cases and known limitations.

Signed-off-by: James Clark <james.clark@arm.com>
---
 .../trace/coresight/coresight-etm4x-reference.rst      | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Documentation/trace/coresight/coresight-etm4x-reference.rst b/Documentation/trace/coresight/coresight-etm4x-reference.rst
index 0439b4006227..ec336575919c 100644
--- a/Documentation/trace/coresight/coresight-etm4x-reference.rst
+++ b/Documentation/trace/coresight/coresight-etm4x-reference.rst
@@ -656,7 +656,15 @@ Bit assignments shown below:-
     ETM_MODE_BB
 
 **description:**
-    Set to enable branch broadcast if supported in hardware [IDR0].
+    Set to enable branch broadcast if supported in hardware [IDR0]. The primary use for this feature
+    is when code is patched dynamically at run time and the full program flow may not be able to be
+    reconstructed using only conditional branches.
+
+    Choosing this option will result in a significant increase in the amount of trace generated -
+    possible danger of overflows, or fewer instructions covered. Note, that this option also
+    overrides any setting of :ref:`ETM_MODE_RETURNSTACK <coresight-return-stack>`, so where a branch
+    broadcast range overlaps a return stack range, return stacks will not be available for that
+    range.
 
 .. _coresight-cycle-accurate:
 
-- 
2.28.0


WARNING: multiple messages have this Message-ID (diff)
From: James Clark <james.clark@arm.com>
To: suzuki.poulose@arm.com, mathieu.poirier@linaro.org,
	coresight@lists.linaro.org, leo.yan@linaro.com,
	mike.leach@linaro.org
Cc: James Clark <james.clark@arm.com>, Leo Yan <leo.yan@linaro.org>,
	John Garry <john.garry@huawei.com>, Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: [PATCH v2 6/6] Documentation: coresight: Expand branch broadcast documentation
Date: Thu, 13 Jan 2022 09:10:55 +0000	[thread overview]
Message-ID: <20220113091056.1297982-7-james.clark@arm.com> (raw)
In-Reply-To: <20220113091056.1297982-1-james.clark@arm.com>

Now that there is a way of enabling branch broadcast via perf, mention
the possible use cases and known limitations.

Signed-off-by: James Clark <james.clark@arm.com>
---
 .../trace/coresight/coresight-etm4x-reference.rst      | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Documentation/trace/coresight/coresight-etm4x-reference.rst b/Documentation/trace/coresight/coresight-etm4x-reference.rst
index 0439b4006227..ec336575919c 100644
--- a/Documentation/trace/coresight/coresight-etm4x-reference.rst
+++ b/Documentation/trace/coresight/coresight-etm4x-reference.rst
@@ -656,7 +656,15 @@ Bit assignments shown below:-
     ETM_MODE_BB
 
 **description:**
-    Set to enable branch broadcast if supported in hardware [IDR0].
+    Set to enable branch broadcast if supported in hardware [IDR0]. The primary use for this feature
+    is when code is patched dynamically at run time and the full program flow may not be able to be
+    reconstructed using only conditional branches.
+
+    Choosing this option will result in a significant increase in the amount of trace generated -
+    possible danger of overflows, or fewer instructions covered. Note, that this option also
+    overrides any setting of :ref:`ETM_MODE_RETURNSTACK <coresight-return-stack>`, so where a branch
+    broadcast range overlaps a return stack range, return stacks will not be available for that
+    range.
 
 .. _coresight-cycle-accurate:
 
-- 
2.28.0


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2022-01-13  9:11 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-13  9:10 [PATCH v2 0/6] coresight: Add config flag to enable branch broadcast James Clark
2022-01-13  9:10 ` James Clark
2022-01-13  9:10 ` [PATCH v2 1/6] " James Clark
2022-01-13  9:10   ` James Clark
2022-01-21 12:43   ` Mike Leach
2022-01-21 12:43     ` Mike Leach
2022-01-28 11:19   ` Suzuki K Poulose
2022-01-28 11:19     ` Suzuki K Poulose
2022-02-02 20:25     ` Mike Leach
2022-02-02 20:25       ` Mike Leach
2022-03-11 14:58       ` James Clark
2022-03-11 14:58         ` James Clark
2022-03-11 15:56         ` Mike Leach
2022-03-11 15:56           ` Mike Leach
2022-04-22 10:18           ` James Clark
2022-04-22 10:18             ` James Clark
2022-05-04  9:46             ` Suzuki K Poulose
2022-05-04  9:46               ` Suzuki K Poulose
2022-01-13  9:10 ` [PATCH v2 2/6] coresight: Fail to open with return stacks if they are unavailable James Clark
2022-01-13  9:10   ` James Clark
2022-01-21 12:42   ` Mike Leach
2022-01-21 12:42     ` Mike Leach
2022-01-28 11:24   ` Suzuki K Poulose
2022-01-28 11:24     ` Suzuki K Poulose
2022-03-11 14:52     ` James Clark
2022-03-11 14:52       ` James Clark
2022-03-11 15:53       ` Mike Leach
2022-03-11 15:53         ` Mike Leach
2022-04-22 10:09         ` James Clark
2022-04-22 10:09           ` James Clark
2022-01-13  9:10 ` [PATCH v2 3/6] perf cs-etm: Update deduction of TRCCONFIGR register for branch broadcast James Clark
2022-01-13  9:10   ` James Clark
2022-01-21 12:44   ` Mike Leach
2022-01-21 12:44     ` Mike Leach
2022-01-28 11:25   ` Suzuki K Poulose
2022-01-28 11:25     ` Suzuki K Poulose
2022-02-15 14:52     ` Arnaldo Carvalho de Melo
2022-02-15 14:52       ` Arnaldo Carvalho de Melo
2022-01-13  9:10 ` [PATCH v2 4/6] Documentation: coresight: Turn numbered subsections into real subsections James Clark
2022-01-13  9:10   ` James Clark
2022-01-21 12:47   ` Mike Leach
2022-01-21 12:47     ` Mike Leach
2022-01-28 11:26   ` Suzuki K Poulose
2022-01-28 11:26     ` Suzuki K Poulose
2022-01-13  9:10 ` [PATCH v2 5/6] Documentation: coresight: Link config options to existing documentation James Clark
2022-01-13  9:10   ` James Clark
2022-01-21 12:49   ` Mike Leach
2022-01-21 12:49     ` Mike Leach
2022-01-13  9:10 ` James Clark [this message]
2022-01-13  9:10   ` [PATCH v2 6/6] Documentation: coresight: Expand branch broadcast documentation James Clark
2022-01-21 12:50   ` Mike Leach
2022-01-21 12:50     ` Mike Leach
2022-01-27 20:26 ` [PATCH v2 0/6] coresight: Add config flag to enable branch broadcast Mathieu Poirier
2022-01-27 20:26   ` Mathieu Poirier

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