linux-kernel - Re: [PATCH v6 3/9] coresight: tmc: add etr_buf_list to store allocated etr

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Message-ID: <9d163813-068b-4921-87fe-8e229692ba2b@arm.com>
Date: Wed, 3 Dec 2025 16:20:47 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Jie Gan <jie.gan@....qualcomm.com>, Mike Leach <mike.leach@...aro.org>,
 James Clark <james.clark@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Tingwei Zhang <tingwei.zhang@....qualcomm.com>,
 Jinlong Mao <jinlong.mao@....qualcomm.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v6 3/9] coresight: tmc: add etr_buf_list to store
 allocated etr_buf

On 08/09/2025 03:01, Jie Gan wrote:
> Add a list to store allocated etr_buf.
> 
> The byte-cntr functionality requires two etr_buf to receive trace data.
> The active etr_buf collects the trace data from source device, while the
> byte-cntr reading function accesses the deactivated etr_buf after is
> has been filled and synced, transferring data to the userspace.
> 
> Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>

This patch alone doesn't make any sense. Please fold it with a proper 
user (i.e. later patches). I can't make any sense of how this will be
used TBH without the following patches and on its own, it doesn't do
much anyways.

Suzuki


> ---
>   drivers/hwtracing/coresight/coresight-tmc-core.c |  1 +
>   drivers/hwtracing/coresight/coresight-tmc.h      | 17 +++++++++++++++++
>   2 files changed, 18 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
> index be964656be93..4d249af93097 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
> @@ -830,6 +830,7 @@ static int __tmc_probe(struct device *dev, struct resource *res)
>   		idr_init(&drvdata->idr);
>   		mutex_init(&drvdata->idr_mutex);
>   		dev_list = &etr_devs;
> +		INIT_LIST_HEAD(&drvdata->etr_buf_list);
>   		break;
>   	case TMC_CONFIG_TYPE_ETF:
>   		desc.groups = coresight_etf_groups;
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
> index 6541a27a018e..292e25d82b62 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -208,6 +208,19 @@ struct tmc_resrv_buf {
>   	s64		len;
>   };
>   
> +/**
> + * @sysfs_buf:	Allocated sysfs_buf.
> + * @is_free:	Indicates whether the buffer is free to choose.
> + * @pos:	Position of the buffer.
> + * @node:	Node in etr_buf_list.
> + */
> +struct etr_buf_node {
> +	struct etr_buf		*sysfs_buf;
> +	bool			is_free;
> +	loff_t			pos;
> +	struct list_head	node;
> +};
> +
>   /**
>    * struct tmc_drvdata - specifics associated to an TMC component
>    * @pclk:	APB clock if present, otherwise NULL
> @@ -242,6 +255,8 @@ struct tmc_resrv_buf {
>    *		(after crash) by default.
>    * @crash_mdata: Reserved memory for storing tmc crash metadata.
>    *		 Used by ETR/ETF.
> + * @etr_buf_list: List that is used to manage allocated etr_buf.
> + * @reading_node: Available buffer for byte-cntr reading.
>    */
>   struct tmc_drvdata {
>   	struct clk		*pclk;
> @@ -271,6 +286,8 @@ struct tmc_drvdata {
>   	struct etr_buf		*perf_buf;
>   	struct tmc_resrv_buf	resrv_buf;
>   	struct tmc_resrv_buf	crash_mdata;
> +	struct list_head        etr_buf_list;
> +	struct etr_buf_node     *reading_node;
>   };
>   
>   struct etr_buf_operations {
>