Messages in this thread | | | Date | Wed, 30 Aug 2023 17:04:57 +0100 | Subject | Re: [PATCH V2] coresight: tmc: Make etr buffer mode user configurable from sysfs | From | Suzuki K Poulose <> |
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Cc: Sudeep
Hi Steve
On 28/08/2023 17:35, Steve Clevenger wrote: > > Hi Suzuki, > > On 8/27/2023 2:35 PM, Suzuki K Poulose wrote: >> Hi Steve >> >> On 26/08/2023 01:14, Steve Clevenger wrote: >>> >>> Unfortunately, I tested with the original patch not [PATCH V2]. I've >>> remedied this. My results below: >>> >>> [root@sut01sys-b212 linux]# cat >>> /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_modes_available >>> auto flat catu >>> [root@sut01sys-b212 linux]# cat >>> /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_mode_preferred >>> auto >>> [root@sut01sys-b212 linux]# echo "catu" > >>> /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_mode_preferred >>> [root@sut01sys-b212 linux]# cat >>> /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_mode_preferred >>> catu >>> >>> As with the V1 patch, auto defaults to catu. >>> >>> I expected to see tmc-sg (former default) as an available mode, but do >>> not. As I recall, the buffer mode defaulted to ETR scatter-gather prior >>> to this patch. Must this capability now be explicitly advertised? I've >>> seen this done as "arm,scatter-gather" in device trees, but not used by >>> Ampere. Perhaps someone can enlighten me. >> >> Yes, you must add that property to the TMC-ETR node (for both DT and >> ACPI). In the past, almost all of the TMC-ETRs (except Juno board) >> locked up the system while using the SG mode (due to the interconnect >> issues, something to do with the transaction). Thus, we decided to >> add a property explicitly enabling this for a given platform. >> >> When you mentioned, it was using TMC-ETR SG mode, how did you verify >> this ? Please be aware that the table allocation code etc are shared >> by both TMC-SG and CATU. >> > > You might recall how this started. I had no way to test the CATU due to > the order the ETR modes defaulted (Flat, ETR-SG, CATU). For test > purposes, I programmatically swapped the ETR-SG/CATU order and could > then verify CATU operation by the driver calling into CATU code. This
So, were you using the DT based boot for the above runs ?
> suggests Flat mode was bypassed, and the driver defaulted to ETR-SG > prior to this hack. This didn't offer the user any control, hence my > feature request. Note that most of the early Ampere self-hosted trace > collection used ETR-SG. Now I can't select it.
> > How is this property described in the ACPI? The "ACPI for CoreSight™ 1.1 > Platform Design Document" (DEN0067) doesn't describe this.
This is not specified in the ACPI platform design document. I can get it fixed. Ideally we need a property describing that the scatter-gather mode is safe to use.
DT uses "arm,scatter-gather" property [0] and this is what we now expect in the ACPI based systems too.
https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/arm/arm,coresight-tmc.yaml#:~:text=71-,72,-73
Does it sound fine ?
Suzuki
> > Thanks, > Steve > > >> Kind regards >> Suzuki >> >>> >>> Steve C. >>> >>> On 8/23/2023 4:10 PM, Steve Clevenger wrote: >>>> >>>> Here's some quick feedback. My system shows two modes available; auto >>>> catu >>>> >>>> etr_buf_mode_current is writable. I expected to see tmc-sg (former >>>> default) listed in etr_buf_modes_available but it doesn't show up. >>>> >>>> Note that both the auto and catu etr_buf_mode_current settings default >>>> to catu. My understanding is auto should revert to the default behavior. >>>> On my system the default was tmc-sg. >>>> >>>> More later. >>>> >>>> [root@sut01sys-b212 kernel]# cat >>>> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_modes_available >>>> >>>> auto catu >>>> [root@sut01sys-b212 kernel]# cat >>>> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_mode_current >>>> catu >>>> [root@sut01sys-b212 kernel]# echo "catu" > >>>> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_mode_current >>>> [root@sut01sys-b212 kernel]# cat >>>> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_mode_current >>>> catu >>>> >>>> Steve C. >>>> >>>> >>>> On 8/21/2023 12:40 PM, Steve Clevenger wrote: >>>>> >>>>> Hi Suzuki, >>>>> >>>>> I may be able to test it this week. You've already pointed me at the >>>>> patch thread(s). The main holdup is I need to merge the 6.6 pending >>>>> platform work in order to use the Ampere ACPI. I couldn't get these >>>>> patches to apply directly to 6.4 last I tried. >>>>> >>>>> Steve C. >>>>> >>>>> On 8/18/2023 2:39 AM, Suzuki K Poulose wrote: >>>>>> 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@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: >>>>>>> >>>>>>> - 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@arm.com/ >>>>>>> >>>>>>> .../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 >>>>>> >>>>>> >>
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