linux-kernel - Re: [PATCH v4 03/10] coresight: tmc: add etr_buf_list to store allocated etr

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Message-ID: <CAJ9a7VijwFKiaZzKsSKPynWapA3ik9d7JLeE+yVNFB0T62iH-Q@mail.gmail.com>
Date: Tue, 5 Aug 2025 11:15:10 +0100
From: Mike Leach <mike.leach@...aro.org>
To: Jie Gan <jie.gan@....qualcomm.com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>, James Clark <james.clark@...aro.org>, 
	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>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
	Tingwei Zhang <tingwei.zhang@....qualcomm.com>, Jinlong Mao <jinlong.mao@....qualcomm.com>, 
	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, Jie Gan <quic_jiegan@...cinc.com>
Subject: Re: [PATCH v4 03/10] coresight: tmc: add etr_buf_list to store
 allocated etr_buf

Hi

On Fri, 25 Jul 2025 at 11:08, Jie Gan <jie.gan@....qualcomm.com> 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>
> ---
>  .../hwtracing/coresight/coresight-tmc-core.c  |  1 +
>  drivers/hwtracing/coresight/coresight-tmc.h   | 19 +++++++++++++++++++
>  2 files changed, 20 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..52ee5f8efe8c 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -208,6 +208,21 @@ struct tmc_resrv_buf {
>         s64             len;
>  };
>
> +/**
> + * @sysfs_buf: Allocated sysfs_buf.
> + * @is_free:   Indicates whether the buffer is free to choose.
> + * @reading:   Indicates whether the buffer is reading.
> + * @pos:       Position of the buffer.
> + * @node:      Node in etr_buf_list.
> + */
> +struct etr_buf_node {
> +       struct etr_buf          *sysfs_buf;
> +       bool                    is_free;
> +       bool                    reading;
> +       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 +257,8 @@ 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 +288,8 @@ 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;

Potential simplification:-
do you need both reading_node here and reading in the etr_buf_node?
reading_node handles the logic for which buffer is being read, while
is_free handles the empty/full logic - reading seems unneeded?

>  };
>
>  struct etr_buf_operations {
> --
> 2.34.1
>

regards

Mike

-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK