Re: [PATCH V2] coresight: tmc: Make etr buffer mode user configurable from sysfs

[Suzuki K Poulose]

Cc: Steve

Steve,

Are you able to test this with CATU ?


On 18/08/2023 09:21, Anshuman Khandual wrote:
> 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@xxxxxxx>
> Cc: Mike Leach <mike.leach@xxxxxxxxxx>
> Cc: James Clark <james.clark@xxxxxxx>
> Cc: Leo Yan <leo.yan@xxxxxxxxxx>
> Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> Cc: coresight@xxxxxxxxxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> This applies on v6.5-rc6
>
> Changes in V2:
>
> - Renamed sysfs file etr_buf_modes_available as buf_modes_available
> - Renamed sysfs file buf_mode_current as buf_mode_preferred
> - Renamed etr_supports_flat_mode() as etr_can_use_flat_mode()
> - Renamed coresight_tmc_groups[] as coresight_etf_groups[]
> - Reused coresight_tmc_group[] for trigger_cntr and buffer_size
> - Fallback trying ETR_MODE_AUTO when user preferred mode fails
> - Moved ETR sysfs details into coresight-tmc-etr.c
> - Dropped etr_can_use_flat_mode() check while offering ETR_MODE_FLAT in sysfs
> - Moved struct etr_buf_hw inside coresight-tmc-etr.c
> - Moved get_etr_buf_hw() and etr_can_use_flat_mode() inside coresight-tmc-etr.c
> - Updated month in Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc
>
> Changes in V1:
>
> https://lore.kernel.org/all/20230728084837.276551-1-anshuman.khandual@xxxxxxx/
>
>   .../testing/sysfs-bus-coresight-devices-tmc   |  16 +++
>   .../hwtracing/coresight/coresight-tmc-core.c  |  15 ++-
>   .../hwtracing/coresight/coresight-tmc-etr.c   | 111 ++++++++++++++++--
>   drivers/hwtracing/coresight/coresight-tmc.h   |   3 +
>   4 files changed, 131 insertions(+), 14 deletions(-)


Looks good to me.

Suzuki