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Message-ID: <f78f72ec-9b57-4373-a7f0-a9295326832b@arm.com>
Date: Thu, 22 Jan 2026 10:07:59 +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>,
Mao Jinlong <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 v10 3/8] coresight: tmc: Introduce sysfs_read_ops to wrap
sysfs read operations
On 22/01/2026 02:08, Jie Gan wrote:
> Introduce sysfs_read_ops as a wrapper, wrap sysfs read operations, for reading
> trace data from the TMC buffer.
>
> Reviewed-by: Mike Leach <mike.leach@...aro.org>
> Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>
> ---
> drivers/hwtracing/coresight/coresight-tmc-core.c | 50 +++++++++++-------------
> drivers/hwtracing/coresight/coresight-tmc.h | 17 ++++++++
> 2 files changed, 40 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
> index 1ea255ffa67c..8b0397a77e57 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
> @@ -232,17 +232,10 @@ static int tmc_read_prepare(struct tmc_drvdata *drvdata)
> {
> int ret = 0;
>
> - switch (drvdata->config_type) {
> - case TMC_CONFIG_TYPE_ETB:
> - case TMC_CONFIG_TYPE_ETF:
> - ret = tmc_read_prepare_etb(drvdata);
> - break;
> - case TMC_CONFIG_TYPE_ETR:
> - ret = tmc_read_prepare_etr(drvdata);
> - break;
> - default:
> + if (drvdata->sysfs_ops)
> + ret = drvdata->sysfs_ops->read_prepare(drvdata);
> + else
> ret = -EINVAL;
> - }
>
> if (!ret)
> dev_dbg(&drvdata->csdev->dev, "TMC read start\n");
> @@ -254,17 +247,10 @@ static int tmc_read_unprepare(struct tmc_drvdata *drvdata)
> {
> int ret = 0;
>
> - switch (drvdata->config_type) {
> - case TMC_CONFIG_TYPE_ETB:
> - case TMC_CONFIG_TYPE_ETF:
> - ret = tmc_read_unprepare_etb(drvdata);
> - break;
> - case TMC_CONFIG_TYPE_ETR:
> - ret = tmc_read_unprepare_etr(drvdata);
> - break;
> - default:
> + if (drvdata->sysfs_ops)
> + ret = drvdata->sysfs_ops->read_unprepare(drvdata);
> + else
> ret = -EINVAL;
> - }
>
> if (!ret)
> dev_dbg(&drvdata->csdev->dev, "TMC read end\n");
> @@ -291,13 +277,8 @@ static int tmc_open(struct inode *inode, struct file *file)
> static ssize_t tmc_get_sysfs_trace(struct tmc_drvdata *drvdata, loff_t pos, size_t len,
> char **bufpp)
> {
> - switch (drvdata->config_type) {
> - case TMC_CONFIG_TYPE_ETB:
> - case TMC_CONFIG_TYPE_ETF:
> - return tmc_etb_get_sysfs_trace(drvdata, pos, len, bufpp);
> - case TMC_CONFIG_TYPE_ETR:
> - return tmc_etr_get_sysfs_trace(drvdata, pos, len, bufpp);
> - }
> + if (drvdata->sysfs_ops)
> + return drvdata->sysfs_ops->get_trace_data(drvdata, pos, len, bufpp);
minor nit: Please could we bail out in tmc_open() if the
drvdata->sysfs_ops is not set. That way, we don't have to sprinkle it
everywhere. And also, we don't expect to see this case anyways.
>
> return -EINVAL;
> }
> @@ -769,6 +750,18 @@ static void register_crash_dev_interface(struct tmc_drvdata *drvdata,
> "Valid crash tracedata found\n");
> }
>
> +static const struct sysfs_read_ops tmc_etb_sysfs_read_ops = {
minor nit: please could we rename the struct type to :
struct tmc_sysfs_ops
and then use
etb_sysfs_ops = {}
etr_sysfs_ops = {}
Rest looks fine to me
Suzuki
> + .read_prepare = tmc_read_prepare_etb,
> + .read_unprepare = tmc_read_unprepare_etb,
> + .get_trace_data = tmc_etb_get_sysfs_trace,
> +};
> +
> +static const struct sysfs_read_ops tmc_etr_sysfs_read_ops = {
> + .read_prepare = tmc_read_prepare_etr,
> + .read_unprepare = tmc_read_unprepare_etr,
> + .get_trace_data = tmc_etr_get_sysfs_trace,
> +};
> +
> static int __tmc_probe(struct device *dev, struct resource *res)
> {
> int ret = 0;
> @@ -828,6 +821,7 @@ static int __tmc_probe(struct device *dev, struct resource *res)
> desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
> desc.ops = &tmc_etb_cs_ops;
> dev_list = &etb_devs;
> + drvdata->sysfs_ops = &tmc_etb_sysfs_read_ops;
> break;
> case TMC_CONFIG_TYPE_ETR:
> desc.groups = coresight_etr_groups;
> @@ -841,6 +835,7 @@ static int __tmc_probe(struct device *dev, struct resource *res)
> mutex_init(&drvdata->idr_mutex);
> dev_list = &etr_devs;
> INIT_LIST_HEAD(&drvdata->etr_buf_list);
> + drvdata->sysfs_ops = &tmc_etr_sysfs_read_ops;
> break;
> case TMC_CONFIG_TYPE_ETF:
> desc.groups = coresight_etf_groups;
> @@ -849,6 +844,7 @@ static int __tmc_probe(struct device *dev, struct resource *res)
> desc.subtype.link_subtype = CORESIGHT_DEV_SUBTYPE_LINK_FIFO;
> desc.ops = &tmc_etf_cs_ops;
> dev_list = &etf_devs;
> + drvdata->sysfs_ops = &tmc_etb_sysfs_read_ops;
> break;
> default:
> pr_err("%s: Unsupported TMC config\n", desc.name);
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
> index 9b3c4e6f0a5e..c9a82ff6cd00 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -221,6 +221,8 @@ struct etr_buf_node {
> struct list_head node;
> };
>
> +struct sysfs_read_ops;
> +
> /**
> * struct tmc_drvdata - specifics associated to an TMC component
> * @atclk: optional clock for the core parts of the TMC.
> @@ -258,6 +260,7 @@ struct etr_buf_node {
> * Used by ETR/ETF.
> * @etr_buf_list: List that is used to manage allocated etr_buf.
> * @reading_node: Available buffer_node for byte-cntr reading.
> + * @sysfs_ops: Read operations for sysfs mode.
> */
> struct tmc_drvdata {
> struct clk *atclk;
> @@ -290,6 +293,20 @@ struct tmc_drvdata {
> struct tmc_resrv_buf crash_mdata;
> struct list_head etr_buf_list;
> struct etr_buf_node *reading_node;
> + const struct sysfs_read_ops *sysfs_ops;
> +};
> +
> +/**
> + * struct sysfs_read_ops - read operations for TMC and its helper devices
> + * @read_prepare: prepare operation.
> + * @read_unprepare: unprepare operation.
> + * @get_trace_data: read operation.
> + */
> +struct sysfs_read_ops {
> + int (*read_prepare)(struct tmc_drvdata *drvdata);
> + int (*read_unprepare)(struct tmc_drvdata *drvdata);
> + ssize_t (*get_trace_data)(struct tmc_drvdata *drvdata, loff_t pos,
> + size_t len, char **bufpp);
> };
>
> struct etr_buf_operations {
>
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