On 8/18/23 13:51, 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.
- FLAT mode with or without IOMMU
- TMC-ETR-SG (scatter gather) mode when available
- 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
This applies on v6.5-rc6
Changes in V2:
Hi Suzuki,
This patch still applies cleanly on current coresight/for-next/queue. But in case, this needs any changes, please do let me know. Thanks !
- Anshuman