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Update PRU UART documentation #708

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2be58f6
fix(linux): Remove PRU SW UART from TOC
jmenti May 14, 2026
c232eab
fix(linux): Enable PRU HW UART doc for am62x and am64x
jmenti May 14, 2026
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1 change: 0 additions & 1 deletion configs/AM335X/AM335X_linux_toc.txt
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Expand Up @@ -88,7 +88,6 @@ linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RemoteProc
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RPMsg
linux/Foundational_Components/PRU-ICSS/RPMsg_Quick_Start_Guide
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/PRU-ICSS_Ethernet
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pru-sw-uart
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart
linux/Foundational_Components/PRU-ICSS-Hardware
linux/Foundational_Components/PRU-ICSS/PRU-EVMs
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1 change: 0 additions & 1 deletion configs/AM437X/AM437X_linux_toc.txt
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Expand Up @@ -89,7 +89,6 @@ linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RemoteProc
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RPMsg
linux/Foundational_Components/PRU-ICSS/RPMsg_Quick_Start_Guide
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/PRU-ICSS_Ethernet
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pru-sw-uart
linux/Foundational_Components/PRU-ICSS-Hardware
linux/Foundational_Components/PRU-ICSS/PRU-EVMs
linux/Foundational_Components/PRU-ICSS-Training
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1 change: 0 additions & 1 deletion configs/AM57X/AM57X_linux_toc.txt
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Expand Up @@ -94,7 +94,6 @@ linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RemoteProc
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RPMsg
linux/Foundational_Components/PRU-ICSS/RPMsg_Quick_Start_Guide
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/PRU-ICSS_Ethernet
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pru-sw-uart
linux/Foundational_Components/PRU-ICSS-Hardware
linux/Foundational_Components/PRU-ICSS/PRU-EVMs
linux/Foundational_Components/PRU-ICSS-Training
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1 change: 1 addition & 0 deletions configs/AM62X/AM62X_linux_toc.txt
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Expand Up @@ -108,6 +108,7 @@ linux/Foundational_Components_PRU_Subsystem
linux/Foundational_Components/PRU-ICSS-Linux-Drivers
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RemoteProc
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RPMsg
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart
linux/Foundational_Components/PRU-ICSS/RPMsg_Quick_Start_Guide
linux/Foundational_Components/PRU-ICSS-Hardware
linux/Foundational_Components/PRU-ICSS/PRU-EVMs
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1 change: 1 addition & 0 deletions configs/AM64X/AM64X_linux_toc.txt
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Expand Up @@ -112,6 +112,7 @@ linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RemoteProc
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/PRU_ICSSG_Ethernet
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/PRU_ICSSG_Ethernet_Switch
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/RPMsg
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart
linux/Foundational_Components/PRU-ICSS/Linux_Drivers/PRU_ICSSG_XDP
linux/Foundational_Components/PRU-ICSS/RPMsg_Quick_Start_Guide
linux/Foundational_Components/PRU-ICSS-Hardware
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79 changes: 0 additions & 79 deletions source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pru-sw-uart.rst
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35 changes: 19 additions & 16 deletions source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst
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Expand Up @@ -3,27 +3,34 @@

.. rubric:: Introduction

As of Processor SDK v7.1, Linux supports the PRU UART peripheral within the
PRU-ICSS, which is based on the industry standard TL16C550.
The kernel driver is at drivers/tty/serial/8250/8250_pruss.c.
.. ifconfig:: CONFIG_part_variant in ('AM62X')

Linux supports the PRU HW UART peripheral within the Programmable Real-Time Unit Subsystem
(PRUSS), which is based on the industry standard TL16C550.

.. rubric:: Support Devices
.. ifconfig:: CONFIG_part_variant in ('AM64X')

- |__PART_FAMILY_DEVICE_NAMES__|
Linux supports the PRU HW UART peripheral within the Programmable Real-Time Unit (PRU) and

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[RedHat.Definitions] Define acronyms and abbreviations (such as 'UART') on first occurrence if they're likely to be unfamiliar.

Raw Output:
{"message": "[RedHat.Definitions] Define acronyms and abbreviations (such as 'UART') on first occurrence if they're likely to be unfamiliar.", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 13, "column": 30}}}, "severity": "INFO"}
Industrial Communication Subsystem - Gigabit (ICSSG) or PRU-ICSSG, which is based on the
industry standard TL16C550.

.. ifconfig:: CONFIG_part_variant in ('AM335X', 'AM437X', 'AM57XX')

Linux supports the PRU HW UART peripheral within the Programmable Real-Time Unit Subsystem
and Industrial Communication Subsystem (PRU-ICSS), which is based on the industry standard
TL16C550.

The kernel driver is at :file:`drivers/tty/serial/8250/8250_pruss.c`.

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[vale] reported by reviewdog 🐶
[RedHat.Slash] Use either 'or' or 'and' in 'drivers/tty'

Raw Output:
{"message": "[RedHat.Slash] Use either 'or' or 'and' in 'drivers/tty'", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 23, "column": 32}}}, "severity": "WARNING"}

.. rubric:: Supported Driver Features

- Baud rates up to 12Mbps
- Hardware flow control


.. rubric:: Unsupported Driver Features

- DMA support


.. rubric:: Kernel Config

The PRUSS UART Linux kernel driver depends on the PRU-ICSS kernel drivers. So
Expand All @@ -46,7 +53,6 @@
Serial drivers --->
<M> TI PRU-ICSS UART support


.. rubric:: Example DT configuration

From am335x-evmsk.dts
Expand All @@ -61,7 +67,6 @@
status = "okay";
};


.. rubric:: Driver Usage

Once the driver is probed, kernel log shows the following message.
Expand All @@ -70,13 +75,11 @@

[ 28.617700] 4a328000.serial: ttyS1 at MMIO 0x4a328000 (irq = 77, base_baud = 12000000) is a 16550A

Therefore the device node /dev/ttyS1 is associated to the PRUSS UART, user
space application can read/write this serial port. For detalls please refer
to :ref:`kernel uart driver usage <linux-kernel-omap-uart-driver-usage>`.
Therefore the device node /dev/ttyS1 is associated with PRUSS UART and

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[RedHat.Definitions] Define acronyms and abbreviations (such as 'UART') on first occurrence if they're likely to be unfamiliar.

Raw Output:
{"message": "[RedHat.Definitions] Define acronyms and abbreviations (such as 'UART') on first occurrence if they're likely to be unfamiliar.", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 78, "column": 63}}}, "severity": "INFO"}

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[vale] reported by reviewdog 🐶
[RedHat.Definitions] Define acronyms and abbreviations (such as 'PRUSS') on first occurrence if they're likely to be unfamiliar.

Raw Output:
{"message": "[RedHat.Definitions] Define acronyms and abbreviations (such as 'PRUSS') on first occurrence if they're likely to be unfamiliar.", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 78, "column": 57}}}, "severity": "INFO"}

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[vale] reported by reviewdog 🐶
[RedHat.PassiveVoice] 'is associated' is passive voice. In general, use active voice. Consult the style guide for acceptable use of passive voice.

Raw Output:
{"message": "[RedHat.PassiveVoice] 'is associated' is passive voice. In general, use active voice. Consult the style guide for acceptable use of passive voice.", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 78, "column": 38}}}, "severity": "INFO"}
user-space applications can read/write to this serial port. For details,
please refer to :ref:`kernel uart driver usage <linux-kernel-omap-uart-driver-usage>`.

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[vale] reported by reviewdog 🐶
[RedHat.CaseSensitiveTerms] Use 'Linux' rather than 'linux'.

Raw Output:
{"message": "[RedHat.CaseSensitiveTerms] Use 'Linux' rather than 'linux'.", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 80, "column": 49}}}, "severity": "WARNING"}

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[vale] reported by reviewdog 🐶
[RedHat.UserReplacedValues] Separate words by underscores in user-replaced values.

Raw Output:
{"message": "[RedHat.UserReplacedValues] Separate words by underscores in user-replaced values.", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 80, "column": 48}}}, "severity": "INFO"}

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[vale] reported by reviewdog 🐶
[RedHat.Spelling] Verify the word 'uart'. It is not in the American English or Red Hat terminology spelling dictionaries used by Vale.

Raw Output:
{"message": "[RedHat.Spelling] Verify the word 'uart'. It is not in the American English or Red Hat terminology spelling dictionaries used by Vale.", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 80, "column": 30}}}, "severity": "WARNING"}

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[vale] reported by reviewdog 🐶
[RedHat.TermsSuggestions] Depending on the context, consider using 'see' rather than 'refer to'.

Raw Output:
{"message": "[RedHat.TermsSuggestions] Depending on the context, consider using 'see' rather than 'refer to'.", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 80, "column": 8}}}, "severity": "INFO"}

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GitHub Actions / vale 

[vale] reported by reviewdog 🐶
[RedHat.DoNotUseTerms] Do not use "please" in technical documentation.

Raw Output:
{"message": "[RedHat.DoNotUseTerms] Do not use \"please\" in technical documentation.", "location": {"path": "source/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.rst", "range": {"start": {"line": 80, "column": 1}}}, "severity": "WARNING"}

.. note::

The index in ttyS1 could vary depending on the serial alias configuration
in the device tree.


The index in ttyS1 could vary depending on the serial alias configuration
in the device tree.
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