linux-kernel - Re: [PATCH v3 3/5] dt-bindings: arm: Add Coresight TMC Control Unit hardware

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Message-ID: <ZsQ5aMkXnyX9mumz@jiegan-gv.ap.qualcomm.com>
Date: Tue, 20 Aug 2024 14:36:24 +0800
From: JieGan <quic_jiegan@...cinc.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
CC: Rob Herring <robh@...nel.org>, Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        James Clark <james.clark@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Maxime Coquelin
	<mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio
	<konrad.dybcio@...aro.org>,
        Jinlong Mao <quic_jinlmao@...cinc.com>, <coresight@...ts.linaro.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        Tingwei Zhang
	<quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        "Tao
 Zhang" <quic_taozha@...cinc.com>,
        Song Chai <quic_songchai@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>
Subject: Re: [PATCH v3 3/5] dt-bindings: arm: Add Coresight TMC Control Unit
 hardware

On Mon, Aug 19, 2024 at 11:51:41AM +0200, Krzysztof Kozlowski wrote:
> On 19/08/2024 10:51, JieGan wrote:
> > On Mon, Aug 19, 2024 at 08:25:33AM +0200, Krzysztof Kozlowski wrote:
> >> On 19/08/2024 03:49, JieGan wrote:
> >>> On Sun, Aug 18, 2024 at 08:28:34AM -0600, Rob Herring wrote:
> >>>> On Mon, Aug 12, 2024 at 10:41:39AM +0800, Jie Gan wrote:
> >>>>> Add binding file to specify how to define a Coresight TMC
> >>>>> Control Unit device in device tree.
> >>>>>
> >>>>> It is responsible for controlling the data filter function
> >>>>> based on the source device's Trace ID for TMC ETR device.
> >>>>> The trace data with that Trace id can get into ETR's buffer
> >>>>> while other trace data gets ignored.
> >>>>>
> >>>>> Signed-off-by: Jie Gan <quic_jiegan@...cinc.com>
> >>>>> ---
> >>>>>  .../bindings/arm/qcom,coresight-ctcu.yaml     | 79 +++++++++++++++++++
> >>>>>  1 file changed, 79 insertions(+)
> >>>>>  create mode 100644 Documentation/devicetree/bindings/arm/qcom,coresight-ctcu.yaml
> >>>>>
> >>>>> diff --git a/Documentation/devicetree/bindings/arm/qcom,coresight-ctcu.yaml b/Documentation/devicetree/bindings/arm/qcom,coresight-ctcu.yaml
> >>>>> new file mode 100644
> >>>>> index 000000000000..7a9580007942
> >>>>> --- /dev/null
> >>>>> +++ b/Documentation/devicetree/bindings/arm/qcom,coresight-ctcu.yaml
> >>>>> @@ -0,0 +1,79 @@
> >>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >>>>> +%YAML 1.2
> >>>>> +---
> >>>>> +$id: http://devicetree.org/schemas/arm/qcom,coresight-ctcu.yaml#
> >>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >>>>> +
> >>>>> +title: CoreSight TMC Control Unit
> >>>>> +
> >>>>> +maintainers:
> >>>>> +  - Yuanfang Zhang <quic_yuanfang@...cinc.com>
> >>>>> +  - Mao Jinlong <quic_jinlmao@...cinc.com>
> >>>>> +  - Jie Gan <quic_jiegan@...cinc.com>
> >>>>> +
> >>>>> +description:
> >>>>> +  The Coresight TMC Control unit controls various Coresight behaviors.
> >>>>> +  It works as a helper device when connected to TMC ETR device.
> >>>>> +  It is responsible for controlling the data filter function based on
> >>>>> +  the source device's Trace ID for TMC ETR device. The trace data with
> >>>>> +  that Trace id can get into ETR's buffer while other trace data gets
> >>>>> +  ignored.
> >>>>
> >>>> Nowhere is TMC defined.
> >>> The Coresight TMC control unit(CTCU) connected to Coresight TMC device via replicator and
> >>> works as a helper device to TMC device.
> >>
> >> Did you understand the feedback or just responding with whatever to get
> >> rid of reviewers?
> > 
> > Sorry for the insufficient clarity in my response, I am just misunderstood the feedback and try
> > to explain the relationship between TMC and CTCU device.
> > 
> > I will add the TMC description to explain what TMC is as shown below:
> > The Trace Memory Controller(TMC) is used for Embedded Trace Buffer(ETB), Embedded Trace FIFO(ETF)
> > and Embedded Trace Router(ETR) configurations. The configuration mode (ETB, ETF, ETR) is
> > discovered at boot time when the device is probed.
> 
> Thanks.
> 
> > 
> >>
> >>>
> >>> The in-ports listed below illustrate their connection to TMC devices.
> >>>
> >>>>
> >>>>> +
> >>>>> +properties:
> >>>>> +  compatible:
> >>>>> +    enum:
> >>>>> +      - qcom,sa8775p-ctcu
> >>>>> +
> >>>>> +  reg:
> >>>>> +    maxItems: 1
> >>>>> +
> >>>>> +  clocks:
> >>>>> +    maxItems: 1
> >>>>> +
> >>>>> +  clock-names:
> >>>>> +    items:
> >>>>> +      - const: apb
> >>>>> +
> >>>>> +  in-ports:
> >>>>
> >>>> Use 'ports' unless you have both in and out ports.
> >>> The ‘in-ports’ and ‘out-ports’ properties will be parsed by ‘of_coresight_get_port_parent’
> >>> and their relationships to other devices will be stored in the coresight_platform_data structure.
> >>>
> >>> for example:
> >>> struct coresight_platform_data {
> >>> 	int nr_inconns;
> >>> 	int nr_outconns;
> >>> 	struct coresight_connection **out_conns;
> >>> 	struct coresight_connection **in_conns;
> >>> };
> >>>
> >>> https://elixir.bootlin.com/linux/v6.11-rc4/source/drivers/hwtracing/coresight/coresight-platform.c#L147
> >>
> >> and? If you respond with some unrelated argument, we will respond with
> >> the same: Use 'ports' unless you have both in and out ports.
> > 
> > Sorry for the insufficient response.
> > 
> > The Coresight driver prefers using ‘in-ports’ and ‘out-ports’ instead of the ‘ports’ property, as each
> > Coresight component needs to specify its input and output directions.
> > 
> > The Coresight system operates by integrating all Coresight components and construting its data flow path
> > based on the defined directions. 
> > 
> > Consequently, the data flow direction cannot be determined when utilizing the ‘ports’ property in the
> > Coresight system.
> 
> It can be determined. Driver knows that there are only in-ports, so you
> cannot have here other direction. Maybe the drivers have somehow this
> hard-coded? But that's a bit annoying limitation.
> 
In Coresight platform driver, the of_coresight_get_port_parent function is used to retrieve the parent of the 'ports' node.
The function is specifically hard-coded to recognize 'in-ports' and 'out-ports'. I think that's the limitation for
'ports' property.

https://elixir.bootlin.com/linux/v6.11-rc4/source/drivers/hwtracing/coresight/coresight-platform.c#L147

Thnaks,
Jie