linux-kernel - Re: [PATCH v11 0/7] Coresight: Add Coresight TMC Control Unit driver

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Message-ID: <44123d40-aae3-4248-95c9-21fb9335020a@linaro.org>
Date: Fri, 14 Feb 2025 11:10:57 +0000
From: James Clark <james.clark@...aro.org>
To: Jie Gan <quic_jiegan@...cinc.com>
Cc: Tingwei Zhang <quic_tingweiz@...cinc.com>,
 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, linux-arm-msm@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach
 <mike.leach@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH v11 0/7] Coresight: Add Coresight TMC Control Unit driver



On 14/02/2025 2:40 am, Jie Gan wrote:
> From: Jie Gan <jie.gan@....qualcomm.com>
> 
> The Coresight TMC Control Unit(CTCU) device hosts miscellaneous configuration
> registers to control various features related to TMC ETR device.
> 
> The CTCU device works as a helper device physically connected to the TMC ETR device.
> ---------------------------------------------------------
>               |ETR0|             |ETR1|
>                . \                 / .
>                .  \               /  .
>                .   \             /   .
>                .    \           /    .
> ---------------------------------------------------
> ETR0ATID0-ETR0ATID3     CTCU    ETR1ATID0-ETR1ATID3
> ---------------------------------------------------
> Each ETR has four ATID registers with 128 bits long in total.
> e.g. ETR0ATID0-ETR0ATID3 registers are used by ETR0 device.
> 
> Based on the trace id which is programed in CTCU ATID register of
> specific ETR, trace data with that trace id can get into ETR's buffer
> while other trace data gets ignored. The number of CTCU ATID registers
> depends on the number of defined TMC ETR devices. For example, two TMC
> ETR devices need eight ATID registers. ETR0 with ETR0ATID0-ETR0ATID3
> and ETR1 with ETR1ATID0-ETRATID3.
> 
> The significant challenge in enabling the data filter function is how
> to collect the trace ID of the source device. The introduction of
> trace_id callback function addresses this challenge. The callback function
> collects trace ID of the device and return it back. The trace ID will be
> stored in the structure called coresight_path and transmitted to helper
> and sink devices.
> 
> The coresight_path structure is created to address how to transmit
> parameters needs by coresight_enable_path/coresight_disbale_path
> functions.
> 
> Here is the definition of the struct coresight_path:
> /**
>   * struct coresight_path - data needed by enable/disable path
>   * @path:               path from source to sink.
>   * @trace_id:           trace_id of the whole path.
>   */
> struct coresight_path {
>          struct list_head                *path;
>          u8                              trace_id;
> };
> 
> The atid_offset mentioned before is the offset to ATID register in CTCU
> device.
> 
> Enabling the source device will configure one bit in the ATID register based
> on its trace ID.
> Disabling the source devices will reset the bit in the AITD register
> based on its trace ID.
> 
> Useage:
> Enable:
> STM device with trace ID 5 and ETR0 is activated.
> Bitmap before the enablement:
> ETR0ATID0:
> 31..................543210
> ==========================
> 0000000000000000000000...0
> ==========================
> 
> Bitmap after the enablement:
> 31..................543210
> ==========================
> 0000000000000...0000100000
> ==========================
> 
> The bit 5 of the ETR0ATID0 register is configured to 1 when enabling the
> STM device.
> 
> Disable:
> STM device with trace ID 5 and ETR0 is activated.
> Bitmap before the disablement:
> ETR0ATID0:
> 31................6543210
> =========================
> 000000000010111...0100000
> =========================
> 
> Bitmap after the disablement
> ETR0ATID0:
> 31................6543210
> =========================
> 000000000010111...0000000
> =========================
> 
> The bit 5 of the ETR0ATID0 register is reset to 0 when disabling the STM
> device.
> 
> Sincere thanks to James Clark for providing an excellent idea to handle
> the trace_id of the path.
> 

No worries! Thanks for working on Coresight too.