Hi all,
When there is some small packet sent from STM to ETR, the small packet could be stuck between source and sink even if manual flush is set when disable ETR. So there is requirement that flush the STM trace periodically after enabling STM to ETR.
STM can generate TRIG_TS packet by writing to offset 0xF0 of the driver STM stimulus port. ETR has ability to initiate a flush on seeing a TRIG_TS packet.
For this requirement, I want to create a sysfs node like trig_ts for STM. When writing 1 to this sysfs node, a timer with 1 second periodicity in STM will start to generate the trig_ts packet to ETR. Once ETR receive the TRIG_TS packet, it will initiate a flush.
Could you please help to provide your comments on this requirement ?
Thanks Jinlong Mao
On 21/02/2023 06:53, Jinlong Mao wrote:
Hi all,
When there is some small packet sent from STM to ETR, the small packet could be stuck between source and sink even if manual flush is set when disable ETR.
Why ? The manual flush should trigger a flush request upstream and eventually cause a flush ? If this doesn't work as expected we should try to get to the bottom of that first, before jumping into "software work arounds".
So there is requirement that flush the STM trace periodically after enabling STM to ETR.
STM can generate TRIG_TS packet by writing to offset 0xF0 of the driver STM stimulus port. ETR has ability to initiate a flush on seeing a TRIG_TS packet.
Why is this different from the "manual flush" and how does it help ? Is it because one of the components doesn't respond properly to the flush request ?
Kind regards Suzuki
For this requirement, I want to create a sysfs node like trig_ts for STM. When writing 1 to this sysfs node, a timer with 1 second periodicity in STM will start to generate the trig_ts packet to ETR. Once ETR receive the TRIG_TS packet, it will initiate a flush.
Could you please help to provide your comments on this requirement ?
Thanks Jinlong Mao
Hi
A couple additional points...
On Wed, 22 Feb 2023 at 11:00, Suzuki K Poulose suzuki.poulose@arm.com wrote:
On 21/02/2023 06:53, Jinlong Mao wrote:
Hi all,
When there is some small packet sent from STM to ETR, the small packet could be stuck between source and sink even if manual flush is set when disable ETR.
Why ? The manual flush should trigger a flush request upstream and eventually cause a flush ? If this doesn't work as expected we should try to get to the bottom of that first, before jumping into "software work arounds".
So there is requirement that flush the STM trace periodically after enabling STM to ETR.
STM can generate TRIG_TS packet by writing to offset 0xF0 of the driver STM stimulus port. ETR has ability to initiate a flush on seeing a TRIG_TS packet.
Why is this different from the "manual flush" and how does it help ? Is it because one of the components doesn't respond properly to the flush request ?
Kind regards Suzuki
For this requirement, I want to create a sysfs node like trig_ts for STM. When writing 1 to this sysfs node, a timer with 1 second periodicity in STM will start to generate the trig_ts packet to ETR.
If this is really needed, then the source writing the data you wish to flush should write to the relevant STM stimulus port. There is no justification for a polling mechanism when the client itself can do the write at a time you believe it to be needed.
Once ETR receive the TRIG_TS packet, it will initiate a flush.
The ETR does not interpret STM packets - this alone will not initiate a flush.
It is possible to program the ETR to respond to the FLUSHIN or TRIGIN signals via the ECT/CTI network of signals, or a trigger event in the trace stream (ATID=0x7D) if a source (in this case the STM) is programmed to output these specific packets when it generates trigger packets in its own protocol. Programming bits in the FFCR control these operations, STM must be programmed separately to generate appropriate output responses on trigger packets.
Regards
Mike
Could you please help to provide your comments on this requirement ?
Thanks Jinlong Mao
On 2/22/2023 8:19 PM, Mike Leach wrote:
Hi
A couple additional points...
On Wed, 22 Feb 2023 at 11:00, Suzuki K Poulose suzuki.poulose@arm.com wrote:
On 21/02/2023 06:53, Jinlong Mao wrote:
Hi all,
When there is some small packet sent from STM to ETR, the small packet could be stuck between source and sink even if manual flush is set when disable ETR.
Why ? The manual flush should trigger a flush request upstream and eventually cause a flush ? If this doesn't work as expected we should try to get to the bottom of that first, before jumping into "software work arounds".
So there is requirement that flush the STM trace periodically after enabling STM to ETR.
STM can generate TRIG_TS packet by writing to offset 0xF0 of the driver STM stimulus port. ETR has ability to initiate a flush on seeing a TRIG_TS packet.
Why is this different from the "manual flush" and how does it help ? Is it because one of the components doesn't respond properly to the flush request ?
Kind regards Suzuki
For this requirement, I want to create a sysfs node like trig_ts for STM. When writing 1 to this sysfs node, a timer with 1 second periodicity in STM will start to generate the trig_ts packet to ETR.
If this is really needed, then the source writing the data you wish to flush should write to the relevant STM stimulus port. There is no justification for a polling mechanism when the client itself can do the write at a time you believe it to be needed.
Once ETR receive the TRIG_TS packet, it will initiate a flush.
The ETR does not interpret STM packets - this alone will not initiate a flush.
It is possible to program the ETR to respond to the FLUSHIN or TRIGIN signals via the ECT/CTI network of signals, or a trigger event in the trace stream (ATID=0x7D) if a source (in this case the STM) is programmed to output these specific packets when it generates trigger packets in its own protocol. Programming bits in the FFCR control these operations, STM must be programmed separately to generate appropriate output responses on trigger packets.
Regards
Mike
Hi Suzuki & Mike,
There is USB case support in our internal device. Data path is that STM data ---> ETR -----> USB ----> PC tool.
On PC tool, it can show the logs from ETR in real time.
When one small packet send from STM to ETR, it can be stuck between STM and ETR. When the packet stuck happens, it will be flushed to ETR only when some other packets generated from STM source or CTI flush commands are sent. If the time is too long to wait for next packets coming, user will consider that issue happens with previous small packet. And user's requirement is that packet from STM can be flushed to ETR automatically instead of sending commands manually.
Is it appropriate to add a sysfs node for STM to generate the trigger packet periodically for such case ?
Thanks Jinlong Mao
Could you please help to provide your comments on this requirement ?
Thanks Jinlong Mao
From: Jinlong Mao quic_jinlmao@quicinc.com Sent: 23 February 2023 06:41 On 2/22/2023 8:19 PM, Mike Leach wrote:
Hi
A couple additional points...
On Wed, 22 Feb 2023 at 11:00, Suzuki K Poulose suzuki.poulose@arm.com
wrote:
On 21/02/2023 06:53, Jinlong Mao wrote:
Hi all,
When there is some small packet sent from STM to ETR, the small packet could be stuck between source and sink even if manual flush is set when disable ETR.
Why ? The manual flush should trigger a flush request upstream and eventually cause a flush ? If this doesn't work as expected we should try to get to the bottom of that first, before jumping into "software work arounds".
So there is requirement that flush the STM trace periodically after enabling STM to ETR.
STM can generate TRIG_TS packet by writing to offset 0xF0 of the driver STM stimulus port. ETR has ability to initiate a flush on seeing a TRIG_TS packet.
Why is this different from the "manual flush" and how does it help ? Is it because one of the components doesn't respond properly to the flush request ?
Kind regards Suzuki
For this requirement, I want to create a sysfs node like trig_ts for STM. When writing 1 to this sysfs node, a timer with 1 second periodicity in STM will start to generate the trig_ts packet to ETR.
If this is really needed, then the source writing the data you wish to flush should write to the relevant STM stimulus port. There is no justification for a polling mechanism when the client itself can do the write at a time you believe it to be needed.
Once ETR receive the TRIG_TS packet, it will initiate a flush.
The ETR does not interpret STM packets - this alone will not initiate a flush.
It is possible to program the ETR to respond to the FLUSHIN or TRIGIN signals via the ECT/CTI network of signals, or a trigger event in the trace stream (ATID=0x7D) if a source (in this case the STM) is programmed to output these specific packets when it generates trigger packets in its own protocol. Programming bits in the FFCR control these operations, STM must be programmed separately to generate appropriate output responses on trigger packets.
Regards
Mike
Hi Suzuki & Mike,
There is USB case support in our internal device. Data path is that STM data ---> ETR -----> USB ----> PC tool.
On PC tool, it can show the logs from ETR in real time.
When one small packet send from STM to ETR, it can be stuck between STM and ETR. When the packet stuck happens, it will be flushed to ETR only when some other packets generated from STM source or CTI flush commands are sent. If the time is too long to wait for next packets coming, user will consider that issue happens with previous small packet. And user's requirement is that packet from STM can be flushed to ETR automatically instead of sending commands manually.
The point of initiating an ATB flush from the ETR is to flush out packets between upstream trace sources and the ETR. The ETR tells upstream sources to flush out their data and acknowledge when complete and this request is passed upwards to all trace sources. In effect the ETR is "pulling" data from all its sources. The mechanism is the same whether it is initiated manually (by writing FFCR) or in response to a trigger on the ATB stream. If it's not working (e.g. because some device between the STM and ETR is not passing on the flush request due to a hardware issue), it doesn't matter how you initiate it at the ETR. So if a manual flush doesn't work then it's not going to work if the flush is in response to an ATB trigger.
Maybe you are simply seeing the effect of sending more data from the STM, that bumps out whatever is ahead of it? So you could achieve the same effect by sending out any kind of data from the STM e.g. a padding packet.
Is it appropriate to add a sysfs node for STM to generate the trigger packet periodically for such case ?
It seems to be solving the problem at the wrong place. If it's useful for the ETR to do a periodic ATB flush, then that would be better done by the kernel periodically initiating the flush manually at the ETR, not by periodically telling one particular trace source (out of many) to send a trigger.
If ATB flush is broken, then a workaround would be to have each trace source periodically send a null packet of some kind - but in that case it there is nothing special about triggers, they could be any kind of padding, and for STM you might be able to generate that by stimulus.
Al
Thanks Jinlong Mao
Could you please help to provide your comments on this requirement ?
Thanks Jinlong Mao
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Hi,
On Thu, 23 Feb 2023 at 06:41, Jinlong Mao quic_jinlmao@quicinc.com wrote:
On 2/22/2023 8:19 PM, Mike Leach wrote:
Hi
A couple additional points...
On Wed, 22 Feb 2023 at 11:00, Suzuki K Poulose suzuki.poulose@arm.com wrote:
On 21/02/2023 06:53, Jinlong Mao wrote:
Hi all,
When there is some small packet sent from STM to ETR, the small packet could be stuck between source and sink even if manual flush is set when disable ETR.
Why ? The manual flush should trigger a flush request upstream and eventually cause a flush ? If this doesn't work as expected we should try to get to the bottom of that first, before jumping into "software work arounds".
So there is requirement that flush the STM trace periodically after enabling STM to ETR.
STM can generate TRIG_TS packet by writing to offset 0xF0 of the driver STM stimulus port. ETR has ability to initiate a flush on seeing a TRIG_TS packet.
Why is this different from the "manual flush" and how does it help ? Is it because one of the components doesn't respond properly to the flush request ?
Kind regards Suzuki
For this requirement, I want to create a sysfs node like trig_ts for STM. When writing 1 to this sysfs node, a timer with 1 second periodicity in STM will start to generate the trig_ts packet to ETR.
If this is really needed, then the source writing the data you wish to flush should write to the relevant STM stimulus port. There is no justification for a polling mechanism when the client itself can do the write at a time you believe it to be needed.
Once ETR receive the TRIG_TS packet, it will initiate a flush.
The ETR does not interpret STM packets - this alone will not initiate a flush.
It is possible to program the ETR to respond to the FLUSHIN or TRIGIN signals via the ECT/CTI network of signals, or a trigger event in the trace stream (ATID=0x7D) if a source (in this case the STM) is programmed to output these specific packets when it generates trigger packets in its own protocol. Programming bits in the FFCR control these operations, STM must be programmed separately to generate appropriate output responses on trigger packets.
Regards
Mike
Hi Suzuki & Mike,
There is USB case support in our internal device. Data path is that STM data ---> ETR -----> USB ----> PC tool.
On PC tool, it can show the logs from ETR in real time.
When one small packet send from STM to ETR, it can be stuck between STM and ETR. When the packet stuck happens, it will be flushed to ETR only when some other packets generated from STM source or CTI flush commands are sent. If the time is too long to wait for next packets coming, user will consider that issue happens with previous small packet. And user's requirement is that packet from STM can be flushed to ETR automatically instead of sending commands manually.
Is it appropriate to add a sysfs node for STM to generate the trigger packet periodically for such case ?
It is likely that the small amount of data is not sufficient to fill a 16byte packet in the ETR formatter, therefore is not being output. Therefore when you do add more data, or initiate a flush then this data will then be output - possibly with padding to complete the formatter frame.
As mentioned before, it should be sufficient to program the ETR to flush on trig in, the STM to emit a trigger packet into the ATB stream when protocol packets such as TRIG_TS is written, and use the STM client that is writing the data to write to the TRIG_TS offset when data needs flushing. This is no different than flushing any standard iostream.
A periodic write should not be needed.
Regards
Mike
Thanks Jinlong Mao
Could you please help to provide your comments on this requirement ?
Thanks Jinlong Mao
-- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK
-
Al Grant -
Jinlong Mao -
Mike Leach -
Suzuki K Poulose