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| author | Anshuman Khandual <anshuman.khandual@arm.com> | 2023-08-18 13:51:12 +0530 |
|---|---|---|
| committer | Suzuki K Poulose <suzuki.poulose@arm.com> | 2023-11-16 11:35:12 +0000 |
| commit | 2373699a3505061cd21625c3f3b70dc3d03a3d8c (patch) | |
| tree | 38dd7dc4f7fafe932ba2e0d368c5e58fde60554e /Documentation/ABI | |
| parent | e5d207b24c54af25fb763af44e2db35347a0f7ee (diff) | |
| download | linux-2373699a3505061cd21625c3f3b70dc3d03a3d8c.tar.gz | |
coresight: tmc: Make etr buffer mode user configurable from sysfs
Currently TMC-ETR automatically selects the buffer mode from all available
methods in the following sequentially fallback manner - also in that order.
1. FLAT mode with or without IOMMU
2. TMC-ETR-SG (scatter gather) mode when available
3. CATU mode when available
But this order might not be ideal for all situations. For example if there
is a CATU connected to ETR, it may be better to use TMC-ETR scatter gather
method, rather than CATU. But hard coding such order changes will prevent
us from testing or using a particular mode. This change provides following
new sysfs tunables for the user to control TMC-ETR buffer mode explicitly,
if required. This adds following new sysfs files for buffer mode selection
purpose explicitly in the user space.
/sys/bus/coresight/devices/tmc_etr<N>/buf_modes_available
/sys/bus/coresight/devices/tmc_etr<N>/buf_mode_preferred
$ cat buf_modes_available
auto flat tmc-sg catu ------------------> Supported TMC-ETR buffer modes
$ echo catu > buf_mode_preferred -------> Explicit buffer mode request
But explicit user request has to be within supported ETR buffer modes only.
These sysfs interface files are exclussive to ETR, and hence these are not
available for other TMC devices such as ETB or ETF etc.
A new auto' mode (i.e ETR_MODE_AUTO) has been added to help fallback to the
existing default behaviour, when user provided preferred buffer mode fails.
ETR_MODE_FLAT and ETR_MODE_AUTO are always available as preferred modes.
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: James Clark <james.clark@arm.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
[Fixup year in sysfs ABI documentation]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230818082112.554638-1-anshuman.khandual@arm.com
Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc index 6aa527296c710..96aafa66b4a58 100644 --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc @@ -91,3 +91,19 @@ Contact: Mathieu Poirier <mathieu.poirier@linaro.org> Description: (RW) Size of the trace buffer for TMC-ETR when used in SYSFS mode. Writable only for TMC-ETR configurations. The value should be aligned to the kernel pagesize. + +What: /sys/bus/coresight/devices/<memory_map>.tmc/buf_modes_available +Date: August 2023 +KernelVersion: 6.7 +Contact: Anshuman Khandual <anshuman.khandual@arm.com> +Description: (Read) Shows all supported Coresight TMC-ETR buffer modes available + for the users to configure explicitly. This file is avaialble only + for TMC ETR devices. + +What: /sys/bus/coresight/devices/<memory_map>.tmc/buf_mode_preferred +Date: August 2023 +KernelVersion: 6.7 +Contact: Anshuman Khandual <anshuman.khandual@arm.com> +Description: (RW) Current Coresight TMC-ETR buffer mode selected. But user could + only provide a mode which is supported for a given ETR device. This + file is available only for TMC ETR devices. |