linux-kernel - Re: [PATCH v5] stm: class: Add MIPI OST protocol support

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Message-ID: <9ed4124e-a6f4-4994-a80e-860a1123c8ba@infradead.org>
Date: Thu, 29 Jan 2026 10:38:50 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Yingchao Deng <yingchao.deng@....qualcomm.com>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Jonathan Corbet <corbet@....net>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, quic_yingdeng@...cinc.com,
 Tingwei Zhang <tingwei.zhang@....qualcomm.com>,
 Yuanfang Zhang <yuanfang.zhang@....qualcomm.com>,
 Jinlong Mao <jinlong.mao@....qualcomm.com>
Subject: Re: [PATCH v5] stm: class: Add MIPI OST protocol support



On 1/29/26 10:31 AM, Randy Dunlap wrote:
> diff --git a/Documentation/trace/p_ost.rst b/Documentation/trace/p_ost.rst
> new file mode 100644
> index 000000000000..df93b889eb4c
> --- /dev/null
> +++ b/Documentation/trace/p_ost.rst
> @@ -0,0 +1,36 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +===================
> +MIPI OST over STP
> +===================
> +
> +The OST(Open System Trace) driver is used with STM class devices to

   The OST (Open System Trace) driver

> +generate standardized trace stream. Trace sources can be identified
> +by different entity ids.
> +
> +CONFIG_STM_PROTO_OST is for p_ost driver enablement. Once this config
> +is enabled, you can select the p_ost protocol by command below:
> +
> +# mkdir /sys/kernel/config/stp-policy/stm0:p_ost.policy
> +
> +The policy name format is extended like this:
> +    <device_name>:<protocol_name>.<policy_name>
> +
> +With coresight-stm device, it will be look like "stm0:p_ost.policy".

   With {a | the} coresight-stm device,

> +
> +With MIPI OST protocol driver, the attributes for each protocol node is:

   With the MIPI OST protocol driver,                                   are:

> +# mkdir /sys/kernel/config/stp-policy/stm0:p_ost.policy/default
> +# ls /sys/kernel/config/stp-policy/stm0:p_ost.policy/default
> +channels  entity    masters
> +
> +The entity here is the set the entity that p_ost supports. Currently

                   is the set of {entities | features} that p_ost supports. Currently

> +p_ost supports ftrace, console and diag entity.

                                           entities.

> +
> +Set entity:
> +# echo 'ftrace' > /sys/kernel/config/stp-policy/stm0:p_ost.policy/default/entity
> +
> +Get available and currently selected (shown in square brackets) entity that p_ost supports:
> +# cat /sys/kernel/config/stp-policy/stm0:p_ost.policy/default/entity
> +[ftrace] console diag
> +
> +See Documentation/ABI/testing/configfs-stp-policy-p_ost for more details.


-- 
~Randy