diff options
Diffstat (limited to 'Documentation/arch/arm64')
| -rw-r--r-- | Documentation/arch/arm64/arm-acpi.rst | 2 | ||||
| -rw-r--r-- | Documentation/arch/arm64/perf.rst | 72 | ||||
| -rw-r--r-- | Documentation/arch/arm64/silicon-errata.rst | 12 |
3 files changed, 83 insertions, 3 deletions
diff --git a/Documentation/arch/arm64/arm-acpi.rst b/Documentation/arch/arm64/arm-acpi.rst index a46c34fa96..e59e4505d0 100644 --- a/Documentation/arch/arm64/arm-acpi.rst +++ b/Documentation/arch/arm64/arm-acpi.rst @@ -130,7 +130,7 @@ When an Arm system boots, it can either have DT information, ACPI tables, or in some very unusual cases, both. If no command line parameters are used, the kernel will try to use DT for device enumeration; if there is no DT present, the kernel will try to use ACPI tables, but only if they are present. -In neither is available, the kernel will not boot. If acpi=force is used +If neither is available, the kernel will not boot. If acpi=force is used on the command line, the kernel will attempt to use ACPI tables first, but fall back to DT if there are no ACPI tables present. The basic idea is that the kernel will not fail to boot unless it absolutely has no other choice. diff --git a/Documentation/arch/arm64/perf.rst b/Documentation/arch/arm64/perf.rst index 1f87b57c23..997fd716b8 100644 --- a/Documentation/arch/arm64/perf.rst +++ b/Documentation/arch/arm64/perf.rst @@ -164,3 +164,75 @@ and should be used to mask the upper bits as needed. https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/arch/arm64/tests/user-events.c .. _tools/lib/perf/tests/test-evsel.c: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/lib/perf/tests/test-evsel.c + +Event Counting Threshold +========================================== + +Overview +-------- + +FEAT_PMUv3_TH (Armv8.8) permits a PMU counter to increment only on +events whose count meets a specified threshold condition. For example if +threshold_compare is set to 2 ('Greater than or equal'), and the +threshold is set to 2, then the PMU counter will now only increment by +when an event would have previously incremented the PMU counter by 2 or +more on a single processor cycle. + +To increment by 1 after passing the threshold condition instead of the +number of events on that cycle, add the 'threshold_count' option to the +commandline. + +How-to +------ + +These are the parameters for controlling the feature: + +.. list-table:: + :header-rows: 1 + + * - Parameter + - Description + * - threshold + - Value to threshold the event by. A value of 0 means that + thresholding is disabled and the other parameters have no effect. + * - threshold_compare + - | Comparison function to use, with the following values supported: + | + | 0: Not-equal + | 1: Equals + | 2: Greater-than-or-equal + | 3: Less-than + * - threshold_count + - If this is set, count by 1 after passing the threshold condition + instead of the value of the event on this cycle. + +The threshold, threshold_compare and threshold_count values can be +provided per event, for example: + +.. code-block:: sh + + perf stat -e stall_slot/threshold=2,threshold_compare=2/ \ + -e dtlb_walk/threshold=10,threshold_compare=3,threshold_count/ + +In this example the stall_slot event will count by 2 or more on every +cycle where 2 or more stalls happen. And dtlb_walk will count by 1 on +every cycle where the number of dtlb walks were less than 10. + +The maximum supported threshold value can be read from the caps of each +PMU, for example: + +.. code-block:: sh + + cat /sys/bus/event_source/devices/armv8_pmuv3/caps/threshold_max + + 0x000000ff + +If a value higher than this is given, then opening the event will result +in an error. The highest possible maximum is 4095, as the config field +for threshold is limited to 12 bits, and the Perf tool will refuse to +parse higher values. + +If the PMU doesn't support FEAT_PMUv3_TH, then threshold_max will read +0, and attempting to set a threshold value will also result in an error. +threshold_max will also read as 0 on aarch32 guests, even if the host +is running on hardware with the feature. diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst index 29fd5213ee..45a7f4932f 100644 --- a/Documentation/arch/arm64/silicon-errata.rst +++ b/Documentation/arch/arm64/silicon-errata.rst @@ -119,6 +119,10 @@ stable kernels. +----------------+-----------------+-----------------+-----------------------------+ | ARM | Cortex-A76 | #1463225 | ARM64_ERRATUM_1463225 | +----------------+-----------------+-----------------+-----------------------------+ +| ARM | Cortex-A76 | #1490853 | N/A | ++----------------+-----------------+-----------------+-----------------------------+ +| ARM | Cortex-A77 | #1491015 | N/A | ++----------------+-----------------+-----------------+-----------------------------+ | ARM | Cortex-A77 | #1508412 | ARM64_ERRATUM_1508412 | +----------------+-----------------+-----------------+-----------------------------+ | ARM | Cortex-A710 | #2119858 | ARM64_ERRATUM_2119858 | @@ -129,6 +133,8 @@ stable kernels. +----------------+-----------------+-----------------+-----------------------------+ | ARM | Cortex-A715 | #2645198 | ARM64_ERRATUM_2645198 | +----------------+-----------------+-----------------+-----------------------------+ +| ARM | Cortex-X1 | #1502854 | N/A | ++----------------+-----------------+-----------------+-----------------------------+ | ARM | Cortex-X2 | #2119858 | ARM64_ERRATUM_2119858 | +----------------+-----------------+-----------------+-----------------------------+ | ARM | Cortex-X2 | #2224489 | ARM64_ERRATUM_2224489 | @@ -137,6 +143,8 @@ stable kernels. +----------------+-----------------+-----------------+-----------------------------+ | ARM | Neoverse-N1 | #1349291 | N/A | +----------------+-----------------+-----------------+-----------------------------+ +| ARM | Neoverse-N1 | #1490853 | N/A | ++----------------+-----------------+-----------------+-----------------------------+ | ARM | Neoverse-N1 | #1542419 | ARM64_ERRATUM_1542419 | +----------------+-----------------+-----------------+-----------------------------+ | ARM | Neoverse-N2 | #2139208 | ARM64_ERRATUM_2139208 | @@ -145,6 +153,8 @@ stable kernels. +----------------+-----------------+-----------------+-----------------------------+ | ARM | Neoverse-N2 | #2253138 | ARM64_ERRATUM_2253138 | +----------------+-----------------+-----------------+-----------------------------+ +| ARM | Neoverse-V1 | #1619801 | N/A | ++----------------+-----------------+-----------------+-----------------------------+ | ARM | MMU-500 | #841119,826419 | N/A | +----------------+-----------------+-----------------+-----------------------------+ | ARM | MMU-600 | #1076982,1209401| N/A | @@ -227,11 +237,9 @@ stable kernels. +----------------+-----------------+-----------------+-----------------------------+ | Rockchip | RK3588 | #3588001 | ROCKCHIP_ERRATUM_3588001 | +----------------+-----------------+-----------------+-----------------------------+ - +----------------+-----------------+-----------------+-----------------------------+ | Fujitsu | A64FX | E#010001 | FUJITSU_ERRATUM_010001 | +----------------+-----------------+-----------------+-----------------------------+ - +----------------+-----------------+-----------------+-----------------------------+ | ASR | ASR8601 | #8601001 | N/A | +----------------+-----------------+-----------------+-----------------------------+ |