This patch series is rebased on coresight-next-v6.12.rc4
* Patches 1 & 2 adds support for allocation of trace buffer pages from
reserved RAM
* Patches 3 & 4 adds support for saving metadata at the time of kernel panic
* Patch 5 adds support for reading trace data captured at the time of panic
* Patches 6 & 7 adds support for disabling coresight blocks at the time of panic
* Patch 8: Gives the full description about this feature as part of documentation
v12 is posted here,
https://lore.kernel.org/linux-arm-kernel/20241129084714.3057080-1-lcherian@…
Changelog from v12:
* Fixed wrong buffer pointer passed to coresigh_insert_barrier_packet
* tmc_read_prepare/unprepare_crashdata need to be called only once and
hence removed from read path and added to tmc_probe
* tmc_read_prepare_crashdata renamed to tmc_prepare_crashdata and
avoid taking locks as its moved to probe function.
* Introduced read status flag, "reading" specific to reserved buffer to keep the
reserved buffer reading independent of the regular buffer.
* open/release ops for reserved buffer has to take care only about the
set/unset the "reading" status flag as the reserved buffer is prepared
during the probe time itself.
* Few other trivial changes
Changelog from v11:
Convert all commands to literal code blocks, that was missed out in v11.
No other code changes.
Changelog from v10:
* Converted all csdev_access_* to readl functions in tmc_panic_sync_*
* Added "tmc" prefix for register snapshots in struct tmc_crash_metadata
* Converted dev_info to dev_dbg in panic handlers
* Converted dsb to dmb in panic handlers
* Fixed marking metadata as invalid when a user is trying to use the
reserved buffer. Earlier this was wrongly set at the time of reading
reserved trace buffer.
* Moved common validation checks to is_tmc_crashdata_valid and minor
code rearrangements for efficiency
* Got rid of sink specific prepare/unprepare invocations
* Got rid of full from struct tmc_resrv_buf
* While reading crashdata, size is now calculated from metadata instead
of relying on reserved buffer size populated by dtb
* Minor documenation fixes
Changelog from v9:
* Add common helper function of_tmc_get_reserved_resource_by_name
for better code reuse
* Reserved buffer validity and crashdata validity has been separated to
avoid interdependence
* New fields added to crash metadata: version, ffcr, ffsr, mode
* Version checks added for metadata validation
* Special file /dev/crash_tmc_xxx would be available only when
crash metadata is valid
* Removed READ_CRASHDATA mode meant for special casing crashdata reads.
Instead, dedicated read function added for crashdata reads from reserved
buffer which is common for both ETR and ETF sinks as well.
* Documentation added to Documentation/tracing/coresight/panic.rst
Changelog from v8:
* Added missing exit path on error in __tmc_probe.
* Few whitespace fixes, checkpatch fixes.
* With perf sessions honouring stop_on_flush sysfs attribute,
removed redundant variable stop_on_flush_en.
Changelog from v7:
* Fixed breakage on perf test -vvvv "arm coresight".
No issues seen with and without "resrv" buffer mode
* Moved the crashdev registration into a separate function.
* Removed redundant variable in tmc_etr_setup_crashdata_buf
* Avoided a redundant memcpy in tmc_panic_sync_etf.
* Tested kernel panic with trace session started uisng perf.
Please see the title "Perf based testing" below for details.
For this, stop_on_flush sysfs attribute is taken into
consideration while starting perf sessions as well.
Changelog from v6:
* Added special device files for reading crashdata, so that
read_prevboot mode flag is removed.
* Added new sysfs TMC device attribute, stop_on_flush.
Stop on flush trigger event is disabled by default.
User need to explicitly enable this from sysfs for panic stop
to work.
* Address parameter for panicstop ETM configuration is
chosen as kernel "panic" address by default.
* Added missing tmc_wait_for_tmcready during panic handling
* Few other misc code rearrangements.
Changelog from v5:
* Fixed issues reported by CONFIG_DEBUG_ATOMIC_SLEEP
* Fixed a memory leak while reading data from /dev/tmc_etrx in
READ_PREVBOOT mode
* Tested reading trace data from crashdump kernel
Changelog from v4:
* Device tree binding
- Description is made more explicit on the usage of reserved memory
region
- Mismatch in memory region names in dts binding and driver fixed
- Removed "mem" suffix from the memory region names
* Rename "struct tmc_register_snapshot" -> "struct tmc_crash_metadata",
since it contains more than register snapshot.
Related variables are named accordingly.
* Rename struct tmc_drvdata members
resrv_buf -> crash_tbuf
metadata -> crash_mdata
* Size field in metadata refers to RSZ register and hence indicates the
size in 32 bit words. ETR metadata follows this convention, the same
has been extended to ETF metadata as well.
* Added crc32 for more robust metadata and tracedata validation.
* Added/modified dev_dbg messages during metadata validation
* Fixed a typo in patch 5 commit description
Changelog from v3:
* Converted the Coresight ETM driver change to a named configuration.
RFC tag has been removed with this change.
* Fixed yaml issues reported by "make dt_binding_check"
* Added names for reserved memory regions 0 and 1
* Added prevalidation checks for metadata processing
* Fixed a regression introduced in RFC v3
- TMC Status register was getting saved wrongly
* Reverted memremap attribute changes from _WB to _WC to match
with the dma map attributes
* Introduced reserved buffer mode specific .sync op.
This fixes a possible crash when reserved buffer mode was used in
normal trace capture, due to unwanted dma maintenance operations.
Linu Cherian (8):
dt-bindings: arm: coresight-tmc: Add "memory-region" property
coresight: tmc-etr: Add support to use reserved trace memory
coresight: core: Add provision for panic callbacks
coresight: tmc: Enable panic sync handling
coresight: tmc: Add support for reading crash data
coresight: tmc: Stop trace capture on FlIn
coresight: config: Add preloaded configuration
Documentation: coresight: Panic support
.../bindings/arm/arm,coresight-tmc.yaml | 26 ++
Documentation/trace/coresight/panic.rst | 362 ++++++++++++++++++
drivers/hwtracing/coresight/Makefile | 2 +-
.../coresight/coresight-cfg-preload.c | 2 +
.../coresight/coresight-cfg-preload.h | 2 +
.../hwtracing/coresight/coresight-cfg-pstop.c | 83 ++++
drivers/hwtracing/coresight/coresight-core.c | 42 ++
.../hwtracing/coresight/coresight-tmc-core.c | 308 ++++++++++++++-
.../hwtracing/coresight/coresight-tmc-etf.c | 92 ++++-
.../hwtracing/coresight/coresight-tmc-etr.c | 184 ++++++++-
drivers/hwtracing/coresight/coresight-tmc.h | 105 +++++
include/linux/coresight.h | 12 +
12 files changed, 1208 insertions(+), 12 deletions(-)
create mode 100644 Documentation/trace/coresight/panic.rst
create mode 100644 drivers/hwtracing/coresight/coresight-cfg-pstop.c
--
2.34.1
When multiple ETMs are enabled simultaneously, the time required
to complete a flush in the process of reading the TMC device node
may exceed the default wait time of 100us. If the TMC capture is
stopped while any ETM has not completed its flush, it can cause
the corresponding CPU to hang.
Fix the by checking the TMCReady bit after the flush. If TMCReady
bit is set, TraceCaptEn bit can be clear; otherwise, return directly
and stop the TMC read.
Signed-off-by: Yuanfang Zhang <quic_yuanfang(a)quicinc.com>
---
drivers/hwtracing/coresight/coresight-tmc-etf.c | 17 +++++++++++++++--
drivers/hwtracing/coresight/coresight-tmc-etr.c | 22 +++++++++++++++++-----
2 files changed, 32 insertions(+), 7 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index d4f641cd9de69488fe3d1c1dc9b5a9eafb55ed59..bded290c42891d782344d9a6e63ebdbed6719133 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -80,11 +80,21 @@ static void tmc_etb_dump_hw(struct tmc_drvdata *drvdata)
return;
}
-static void __tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
+static int __tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
{
+ int rc;
+
CS_UNLOCK(drvdata->base);
tmc_flush_and_stop(drvdata);
+
+ rc = tmc_wait_for_tmcready(drvdata);
+ if (rc) {
+ dev_err(&drvdata->csdev->dev,
+ "Failed to disable : TMC is not ready\n");
+ CS_LOCK(drvdata->base);
+ return rc;
+ }
/*
* When operating in sysFS mode the content of the buffer needs to be
* read before the TMC is disabled.
@@ -94,6 +104,7 @@ static void __tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
tmc_disable_hw(drvdata);
CS_LOCK(drvdata->base);
+ return 0;
}
static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
@@ -650,7 +661,9 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
ret = -EINVAL;
goto out;
}
- __tmc_etb_disable_hw(drvdata);
+ ret = __tmc_etb_disable_hw(drvdata);
+ if (ret)
+ goto out;
}
drvdata->reading = true;
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index a48bb85d0e7f44a25b813f3c828cc3d705d16012..63a1f7501562fa0b5c2fe6ea53dce4d82842bec3 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1135,11 +1135,21 @@ static void tmc_etr_sync_sysfs_buf(struct tmc_drvdata *drvdata)
}
}
-static void __tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
+static int __tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
{
+ int rc;
+
CS_UNLOCK(drvdata->base);
tmc_flush_and_stop(drvdata);
+
+ rc = tmc_wait_for_tmcready(drvdata);
+ if (rc) {
+ dev_err(&drvdata->csdev->dev,
+ "Failed to disable : TMC is not ready\n");
+ CS_LOCK(drvdata->base);
+ return rc;
+ }
/*
* When operating in sysFS mode the content of the buffer needs to be
* read before the TMC is disabled.
@@ -1150,7 +1160,7 @@ static void __tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
tmc_disable_hw(drvdata);
CS_LOCK(drvdata->base);
-
+ return 0;
}
void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
@@ -1779,9 +1789,11 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
}
/* Disable the TMC if we are trying to read from a running session. */
- if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS)
- __tmc_etr_disable_hw(drvdata);
-
+ if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS) {
+ ret = __tmc_etr_disable_hw(drvdata);
+ if (ret)
+ goto out;
+ }
drvdata->reading = true;
out:
spin_unlock_irqrestore(&drvdata->spinlock, flags);
---
base-commit: fac04efc5c793dccbd07e2d59af9f90b7fc0dca4
change-id: 20250103-fix_cpu_hung-b5a95179ada4
Best regards,
--
Yuanfang Zhang <quic_yuanfang(a)quicinc.com>
On 24/01/2025 7:25 am, Jie Gan wrote:
> Add 'struct coresight_path' to store the data that is needed by
> coresight_enable_path/coresight_disable_path. The structure
> will be transmitted to the helper and sink device to enable
> related funcationalities.
>
> Signed-off-by: Jie Gan <quic_jiegan(a)quicinc.com>
> ---
[...]
> /*
> * If we still have access to the event_data via handle,
> @@ -595,11 +599,11 @@ static void etm_event_stop(struct perf_event *event, int mode)
> if (!csdev)
> return;
>
> - path = etm_event_cpu_path(event_data, cpu);
> - if (!path)
> + cs_path = etm_event_cpu_path(event_data, cpu);
> + if (!cs_path)
I don't think renaming 'path' to 'cs_path' is worth the churn. It's in a
lot of places in this change, but I think path is already good enough.
> return;
>
> - sink = coresight_get_sink(path);
> + sink = coresight_get_sink(cs_path->path);
coresight_get_sink() is always called with cs_path->path, so we might as
well make it take a whole path struct. The same with any of the other
functions that operate on path like coresight_get_source().
Proof of concept to support CTCU device. Applies to Jie's patchset in
the parent email. I think this would be a good simplification, it
removes some code and makes things a bit clearer, and works for both the
old and new CTCU requirements. It will require merging into the parent
patchset somehow as it undoes some of those changes.
James Clark (3):
coresight: Don't save handle in path
coresight: Export coresight_get_sink()
coresight: Alloc trace ID after building the path
drivers/hwtracing/coresight/coresight-core.c | 107 +++++++++++++-----
drivers/hwtracing/coresight/coresight-dummy.c | 9 +-
drivers/hwtracing/coresight/coresight-etb10.c | 8 +-
.../hwtracing/coresight/coresight-etm-perf.c | 20 ++--
drivers/hwtracing/coresight/coresight-etm.h | 1 -
.../coresight/coresight-etm3x-core.c | 84 ++------------
.../coresight/coresight-etm3x-sysfs.c | 3 +-
.../coresight/coresight-etm4x-core.c | 83 ++------------
.../coresight/coresight-etm4x-sysfs.c | 4 +-
drivers/hwtracing/coresight/coresight-etm4x.h | 1 -
drivers/hwtracing/coresight/coresight-priv.h | 17 +--
drivers/hwtracing/coresight/coresight-stm.c | 5 +-
drivers/hwtracing/coresight/coresight-sysfs.c | 6 +-
.../hwtracing/coresight/coresight-tmc-etf.c | 9 +-
.../hwtracing/coresight/coresight-tmc-etr.c | 13 +--
drivers/hwtracing/coresight/coresight-tmc.h | 2 +-
drivers/hwtracing/coresight/coresight-tpda.c | 3 +-
drivers/hwtracing/coresight/coresight-tpdm.c | 3 +-
drivers/hwtracing/coresight/coresight-tpiu.c | 2 +-
drivers/hwtracing/coresight/coresight-trbe.c | 4 +-
drivers/hwtracing/coresight/ultrasoc-smb.c | 8 +-
include/linux/coresight.h | 25 +++-
22 files changed, 159 insertions(+), 258 deletions(-)
--
2.34.1
On 29/01/2025 1:02 pm, Jie Gan wrote:
>
>
> On 1/29/2025 6:35 PM, James Clark wrote:
>>
>>
>> On 29/01/2025 12:46 am, Jie Gan wrote:
>>>
>>>
>>> On 1/28/2025 7:55 PM, James Clark wrote:
>>>>
>>>>
>>>> On 24/01/2025 7:25 am, Jie Gan wrote:
>>>>> The Coresight TMC Control Unit hosts miscellaneous configuration
>>>>> registers
>>>>> which control various features related to TMC ETR sink.
>>>>>
>>>>> Based on the trace ID, which is programmed in the related CTCU ATID
>>>>> register of a specific ETR, trace data with that trace ID gets into
>>>>> the ETR buffer, while other trace data gets dropped.
>>>>>
>>>>> Enabling source device sets one bit of the ATID register based on
>>>>> source device's trace ID.
>>>>> Disabling source device resets the bit according to the source
>>>>> device's trace ID.
>>>>>
>>>>> Signed-off-by: Jie Gan <quic_jiegan(a)quicinc.com>
>>>>> ---
>>>>> drivers/hwtracing/coresight/Kconfig | 12 +
>>>>> drivers/hwtracing/coresight/Makefile | 1 +
>>>>> drivers/hwtracing/coresight/coresight-ctcu.c | 276 ++++++++++++++
>>>>> + ++++
>>>>> drivers/hwtracing/coresight/coresight-ctcu.h | 30 ++
>>>>> include/linux/coresight.h | 3 +-
>>>>> 5 files changed, 321 insertions(+), 1 deletion(-)
>>>>> create mode 100644 drivers/hwtracing/coresight/coresight-ctcu.c
>>>>> create mode 100644 drivers/hwtracing/coresight/coresight-ctcu.h
>>>> >
>>>>
>>>> [...]
>>>>
>>>>> +/*
>>>>> + * ctcu_set_etr_traceid: Retrieve the ATID offset and trace ID.
>>>>> + *
>>>>> + * Returns 0 indicates success. None-zero result means failure.
>>>>> + */
>>>>> +static int ctcu_set_etr_traceid(struct coresight_device *csdev,
>>>>> struct coresight_path *cs_path,
>>>>> + bool enable)
>>>>> +{
>>>>> + struct coresight_device *sink = coresight_get_sink(cs_path-
>>>>> >path);
>>>>> + struct ctcu_drvdata *drvdata = dev_get_drvdata(csdev-
>>>>> >dev.parent);
>>>>> + u8 trace_id = cs_path->trace_id;
>>>>> + int port_num;
>>>>> +
>>>>> + if ((sink == NULL) || !IS_VALID_CS_TRACE_ID(trace_id) ||
>>>>> IS_ERR_OR_NULL(drvdata)) {
>>>>> + dev_err(&csdev->dev, "Invalid parameters\n");
>>>>> + return -EINVAL;
>>>>> + }
>>>>> +
>>>>> + port_num = ctcu_get_active_port(sink, csdev);
>>>>> + if (port_num < 0)
>>>>> + return -EINVAL;
>>>>> +
>>>>> + /*
>>>>> + * Skip the disable session if more than one TPDM device that
>>>>> + * connected to the same TPDA device has been enabled.
>>>>> + */
>>>>> + if (enable)
>>>>> + atomic_inc(&drvdata->traceid_refcnt[port_num][trace_id]);
>>>>> + else {
>>>>> + if (atomic_dec_return(&drvdata->traceid_refcnt[port_num]
>>>>> [trace_id]) > 0) {
>>>>> + dev_dbg(&csdev->dev, "Skip the disable session\n");
>>>>> + return 0;
>>>>> + }
>>>>> + }
>>>>> +
>>>>> + dev_dbg(&csdev->dev, "traceid is %d\n", cs_path->trace_id);
>>>>> +
>>>>> + return __ctcu_set_etr_traceid(csdev, trace_id, port_num, enable);
>>>>
>>>> Hi Jie,
>>>>
>>>> Using atomic_dec_return() here doesn't prevent
>>>> __ctcu_set_etr_traceid() from running concurrent enable and
>>>> disables. Once you pass the atomic_dec_return() a second call to
>>>> enable it will mess it up.
>>>>
>>>> I think you need a spinlock around the whole thing and then the
>>>> refcounts don't need to be atomics.
>>>>
>>> Hi, James
>>> Thanks for comment. I may not fully tested my codes here. What I was
>>> thinking is there's no way the refcnt could become a negative number
>>> under current framework. So I just added spinlock in
>>> __ctcu_set_etr_traceid() to ensure concurrent sessions correctly
>>> manipulate the register.
>>>
>>> As the trace_id related to the bit of the ATID register, I think the
>>> concurrent processes are working fine with spinlock around read/write
>>> register.
>>>
>>> I may not fully got your point here. Please help me to correct it.
>>>
>>> Thanks,
>>> Jie
>>>
>>>
>>
>> No it can't become negative, but the refcount can be a different state
>> to the one that was actually written:
>>
>>
>> CPU0 CPU1
>> ---- ----
>> ctcu_set_etr_traceid(enable)
>> ctcu_set_etr_traceid(disable)
>> atomic_inc()
>> recount == 1
>> atomic_dec()
>> recount == 0
>>
>> __ctcu_set_etr_traceid(disable)
>> Lock and write disable state to
>> device
>>
>> __ctcu_set_etr_traceid(enable)
>> Lock and write enable state to
>> device
>>
>>
>> As you can see this leaves the device in an enabled state but the
>> refcount is 0.
> Yes, you are right. I didnt consider this scenario. We definitely need
> spinlock here.
>
>>
>> This is also quite large if you use atomic types:
>>
>> /* refcnt for each traceid of each sink */
>> atomic_t traceid_refcnt[ATID_MAX_NUM][CORESIGHT_TRACE_ID_RES_TOP];
>>
>> Presumably you can't have the refcount for each ID be higher than the
>> max number of TPDMs connected? If you make the locked area a bit wider
>> you don't need atomic types and also solve the above problem. So you
>> could do u8, or DECLARE_BITMAP() and bitmap_read() etc to read 3 bit
>> values. Or however wide it needs to be.
> The original purpose of using atomic here is trying to narrow the locked
> area.
>
> I think u8 is ok here.
> u8 traceid_refcnt[ATID_MAX_NUM][CORESIGHT_TRACE_ID_RES_TOP] will cost
> 224 bytes, I think it's acceptable here.
>
> Thanks,
> Jie
>
Yep u8 sounds ok then
On 29/01/2025 12:46 am, Jie Gan wrote:
>
>
> On 1/28/2025 7:55 PM, James Clark wrote:
>>
>>
>> On 24/01/2025 7:25 am, Jie Gan wrote:
>>> The Coresight TMC Control Unit hosts miscellaneous configuration
>>> registers
>>> which control various features related to TMC ETR sink.
>>>
>>> Based on the trace ID, which is programmed in the related CTCU ATID
>>> register of a specific ETR, trace data with that trace ID gets into
>>> the ETR buffer, while other trace data gets dropped.
>>>
>>> Enabling source device sets one bit of the ATID register based on
>>> source device's trace ID.
>>> Disabling source device resets the bit according to the source
>>> device's trace ID.
>>>
>>> Signed-off-by: Jie Gan <quic_jiegan(a)quicinc.com>
>>> ---
>>> drivers/hwtracing/coresight/Kconfig | 12 +
>>> drivers/hwtracing/coresight/Makefile | 1 +
>>> drivers/hwtracing/coresight/coresight-ctcu.c | 276 +++++++++++++++++++
>>> drivers/hwtracing/coresight/coresight-ctcu.h | 30 ++
>>> include/linux/coresight.h | 3 +-
>>> 5 files changed, 321 insertions(+), 1 deletion(-)
>>> create mode 100644 drivers/hwtracing/coresight/coresight-ctcu.c
>>> create mode 100644 drivers/hwtracing/coresight/coresight-ctcu.h
>> >
>>
>> [...]
>>
>>> +/*
>>> + * ctcu_set_etr_traceid: Retrieve the ATID offset and trace ID.
>>> + *
>>> + * Returns 0 indicates success. None-zero result means failure.
>>> + */
>>> +static int ctcu_set_etr_traceid(struct coresight_device *csdev,
>>> struct coresight_path *cs_path,
>>> + bool enable)
>>> +{
>>> + struct coresight_device *sink = coresight_get_sink(cs_path->path);
>>> + struct ctcu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
>>> + u8 trace_id = cs_path->trace_id;
>>> + int port_num;
>>> +
>>> + if ((sink == NULL) || !IS_VALID_CS_TRACE_ID(trace_id) ||
>>> IS_ERR_OR_NULL(drvdata)) {
>>> + dev_err(&csdev->dev, "Invalid parameters\n");
>>> + return -EINVAL;
>>> + }
>>> +
>>> + port_num = ctcu_get_active_port(sink, csdev);
>>> + if (port_num < 0)
>>> + return -EINVAL;
>>> +
>>> + /*
>>> + * Skip the disable session if more than one TPDM device that
>>> + * connected to the same TPDA device has been enabled.
>>> + */
>>> + if (enable)
>>> + atomic_inc(&drvdata->traceid_refcnt[port_num][trace_id]);
>>> + else {
>>> + if (atomic_dec_return(&drvdata->traceid_refcnt[port_num]
>>> [trace_id]) > 0) {
>>> + dev_dbg(&csdev->dev, "Skip the disable session\n");
>>> + return 0;
>>> + }
>>> + }
>>> +
>>> + dev_dbg(&csdev->dev, "traceid is %d\n", cs_path->trace_id);
>>> +
>>> + return __ctcu_set_etr_traceid(csdev, trace_id, port_num, enable);
>>
>> Hi Jie,
>>
>> Using atomic_dec_return() here doesn't prevent
>> __ctcu_set_etr_traceid() from running concurrent enable and disables.
>> Once you pass the atomic_dec_return() a second call to enable it will
>> mess it up.
>>
>> I think you need a spinlock around the whole thing and then the
>> refcounts don't need to be atomics.
>>
> Hi, James
> Thanks for comment. I may not fully tested my codes here. What I was
> thinking is there's no way the refcnt could become a negative number
> under current framework. So I just added spinlock in
> __ctcu_set_etr_traceid() to ensure concurrent sessions correctly
> manipulate the register.
>
> As the trace_id related to the bit of the ATID register, I think the
> concurrent processes are working fine with spinlock around read/write
> register.
>
> I may not fully got your point here. Please help me to correct it.
>
> Thanks,
> Jie
>
>
No it can't become negative, but the refcount can be a different state
to the one that was actually written:
CPU0 CPU1
---- ----
ctcu_set_etr_traceid(enable)
ctcu_set_etr_traceid(disable)
atomic_inc()
recount == 1
atomic_dec()
recount == 0
__ctcu_set_etr_traceid(disable)
Lock and write disable state to
device
__ctcu_set_etr_traceid(enable)
Lock and write enable state to
device
As you can see this leaves the device in an enabled state but the
refcount is 0.
This is also quite large if you use atomic types:
/* refcnt for each traceid of each sink */
atomic_t traceid_refcnt[ATID_MAX_NUM][CORESIGHT_TRACE_ID_RES_TOP];
Presumably you can't have the refcount for each ID be higher than the
max number of TPDMs connected? If you make the locked area a bit wider
you don't need atomic types and also solve the above problem. So you
could do u8, or DECLARE_BITMAP() and bitmap_read() etc to read 3 bit
values. Or however wide it needs to be.
On 24/01/2025 7:25 am, Jie Gan wrote:
> The Coresight TMC Control Unit hosts miscellaneous configuration registers
> which control various features related to TMC ETR sink.
>
> Based on the trace ID, which is programmed in the related CTCU ATID
> register of a specific ETR, trace data with that trace ID gets into
> the ETR buffer, while other trace data gets dropped.
>
> Enabling source device sets one bit of the ATID register based on
> source device's trace ID.
> Disabling source device resets the bit according to the source
> device's trace ID.
>
> Signed-off-by: Jie Gan <quic_jiegan(a)quicinc.com>
> ---
> drivers/hwtracing/coresight/Kconfig | 12 +
> drivers/hwtracing/coresight/Makefile | 1 +
> drivers/hwtracing/coresight/coresight-ctcu.c | 276 +++++++++++++++++++
> drivers/hwtracing/coresight/coresight-ctcu.h | 30 ++
> include/linux/coresight.h | 3 +-
> 5 files changed, 321 insertions(+), 1 deletion(-)
> create mode 100644 drivers/hwtracing/coresight/coresight-ctcu.c
> create mode 100644 drivers/hwtracing/coresight/coresight-ctcu.h
>
[...]
> +/*
> + * ctcu_set_etr_traceid: Retrieve the ATID offset and trace ID.
> + *
> + * Returns 0 indicates success. None-zero result means failure.
> + */
> +static int ctcu_set_etr_traceid(struct coresight_device *csdev, struct coresight_path *cs_path,
> + bool enable)
> +{
> + struct coresight_device *sink = coresight_get_sink(cs_path->path);
> + struct ctcu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> + u8 trace_id = cs_path->trace_id;
> + int port_num;
> +
> + if ((sink == NULL) || !IS_VALID_CS_TRACE_ID(trace_id) || IS_ERR_OR_NULL(drvdata)) {
> + dev_err(&csdev->dev, "Invalid parameters\n");
> + return -EINVAL;
> + }
> +
> + port_num = ctcu_get_active_port(sink, csdev);
> + if (port_num < 0)
> + return -EINVAL;
> +
> + /*
> + * Skip the disable session if more than one TPDM device that
> + * connected to the same TPDA device has been enabled.
> + */
> + if (enable)
> + atomic_inc(&drvdata->traceid_refcnt[port_num][trace_id]);
> + else {
> + if (atomic_dec_return(&drvdata->traceid_refcnt[port_num][trace_id]) > 0) {
> + dev_dbg(&csdev->dev, "Skip the disable session\n");
> + return 0;
> + }
> + }
> +
> + dev_dbg(&csdev->dev, "traceid is %d\n", cs_path->trace_id);
> +
> + return __ctcu_set_etr_traceid(csdev, trace_id, port_num, enable);
Hi Jie,
Using atomic_dec_return() here doesn't prevent __ctcu_set_etr_traceid()
from running concurrent enable and disables. Once you pass the
atomic_dec_return() a second call to enable it will mess it up.
I think you need a spinlock around the whole thing and then the
refcounts don't need to be atomics.