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Dss ds docs #732

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d91a376
feat(pm_low_power_modes): add DSS plus Deep Sleep mode for AM62LX
akashdeep-ti Jul 3, 2026
9d9ef33
feat(linux): add DSS plus Deep Sleep power measurements
akashdeep-ti Jul 3, 2026
f7d3760
feat(linux): add DSS plus Deep Sleep mode to release notes
akashdeep-ti Jul 3, 2026
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14 changes: 13 additions & 1 deletion source/devices/AM62LX/linux/Linux_Performance_Guide.rst
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Expand Up @@ -854,7 +854,19 @@ Power Performance
^^^^^^^^^^^^^^^^^

These are power measurements taken while the device is in various low power modes like
Deep Sleep, RTC Only + DDR, and RTC Only.
DSS plus Deep Sleep, Deep Sleep, RTC Only + DDR, and RTC Only.

.. csv-table:: DSS plus Deep Sleep Power Performance
:header: "Rail name","Rail voltage(V)","Power (mW)"

"vdd_core", "0.75", "44.66"
"soc_dvdd_1v8", "1.80", "1.77"
"soc_dvdd_3v3", "3.30", "3.64"
"vdda_1v8", "1.80", "18.82"
"vdd_lpddr4_pmic2", "1.10", "1.06"
"vdd_rtc", "0.75", "0.03"
"vdd_rtc_1v8", "1.80", "0.01"
"Total"," ","69.99"

.. csv-table:: Deep Sleep Power Performance
:header: "Rail name","Rail voltage(V)","Power (mW)"
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1 change: 1 addition & 0 deletions source/devices/AM62LX/linux/Release_Specific_Release_Notes.rst
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Expand Up @@ -83,6 +83,7 @@ What's new
- U-Boot: :ref:`Key writer lite Programming <key-writer-lite-label>`
- Kernel: :ref:`DTHEv2 Crypto Accelerator <DTHEv2-Crypto-Accelerator>`
- RT Kernel : Real-Time Linux Interrupt Latency numbers here - :ref:`RT Interrupt Latencies <RT-linux-performance>`
- Power Management: DSS plus Deep Sleep mode - Display subsystem self-refresh with static image during suspend - :ref:`Low Power Modes <lpm_modes>`
- Support for Wifi with M2 CC33xx cards - :ref:`How to Enable M.2-CC33xx in Linux <enable_m2cc3301>`
- Out-of-Box experience based on LVGL (Light and Versatile Graphics Library) - :ref:`TI LVGL Demo - User Guide <TI-LVGL-Demo-User-Guide-label>`
- Security: Post Quantum Cryptography using Module Lattice (ML) Key Encapsulation Mechanism (KEM) or ML-KEM, ML Digital Signature Algorithm (DSA) or ML-DSA, and Stateless Hash-Based (SLH) DSA or SLH-DSA - :ref:`Post Quantum Cryptography <post_quantum_cryptography>`
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207 changes: 180 additions & 27 deletions ...ce/linux/Foundational_Components/Power_Management/pm_am62lx_low_power_modes.rst
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Expand Up @@ -18,6 +18,7 @@ to highest power consumption):
#. RTC Only
#. RTC Only Plus DDR
#. Deep Sleep
#. DSS plus Deep Sleep

RTC Only
********
Expand Down Expand Up @@ -172,36 +173,188 @@ In order to enter DeepSleep,
[ 88.649913] PM: suspend exit
root@am62lxx-evm:~#

DSS plus Deep Sleep
*******************

DSS plus Deep Sleep is a low-power mode where the Display Subsystem (DSS) is kept on to display
a static image while the rest of the system enters Deep Sleep. This mode is useful for
applications that need to maintain visual output during system suspend, such as displaying
status information, warnings, or other static content while minimizing overall power consumption.

In DSS plus Deep Sleep mode, the system state is retained in RAM with DDR in self-refresh,
similar to standard Deep Sleep. The key difference is that the DSS remains active and
powered to continue driving the display with a static framebuffer. The DSS has a self-refresh
feature that allows it to fetch the framebuffer from its internal memory instead of accessing
DDR, which helps reduce power consumption while maintaining display output.

How It Works
============

DSS plus Deep Sleep requires two display properties to be enabled together:

**SELF_REFRESH**

This property enables the DSS hardware to replay the last displayed frame from its internal
on-chip memory (a small FIFO buffer) instead of continuously fetching from DDR. This
significantly reduces memory bandwidth and power consumption during suspend.

The AM62L-DSS has a 20 KB FIFO buffer. For the self-refresh feature to work, your static
image must fit within this buffer. The size is calculated as:

**Frame Size = Width × Height × Bytes-per-pixel**

For RGB format (3 bytes per pixel), this means:

**Width × Height × 3 ≤ 20,480 bytes**

For example, a 50×50 RGB image requires 50 × 50 × 3 = 7,500 bytes, which fits comfortably
within the limit. If your frame is too large, self-refresh will not activate.

**ALWAYS_ON_DISPLAY**

This property keeps the display pipeline powered on during system suspend. Without this,
the display would be powered off even if self-refresh is enabled. Together with self-refresh,
it ensures the static frame remains visible throughout the suspend period.

Using both properties together enables DSS plus Deep Sleep mode: the display stays on showing
a static frame from internal memory while the rest of the system is suspended.

Entering DSS plus Deep Sleep Mode
=================================

Entering DSS plus Deep Sleep requires several steps to configure the display subsystem properly.
First, stop any display manager service that may be actively managing the display:

.. code-block:: console

root@am62lxx-evm:~# systemctl stop emptty.service

Next, enable the DSS self-refresh feature. This configures the display controller to fetch
the framebuffer from its internal memory instead of accessing DDR. The property ID 35
corresponds to the SELF_REFRESH plane property:

.. code-block:: console

root@am62lxx-evm:~# modetest -M tidss -w 35:SELF_REFRESH:1 # 35 is the SELF_REFRESH plane property ID
opened device `TI Keystone DSS` on driver `tidss` (version 1.0.0 at 0)

Display a static image on the screen that will remain visible during suspend. This example
uses GStreamer to display a test pattern:

.. code-block:: console

root@am62lxx-evm:~# gst-launch-1.0 videotestsrc pattern=ball ! video/x-raw, width=50, height=50, framerate=60/1, format=RGB ! fpsdisplaysink text-overlay=false video-sink="kmssink can-scale=false sync=false" sync=false -v
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0/GstKMSSink:kmssink0: display-width = 800
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0/GstKMSSink:kmssink0: display-height = 480
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0/GstKMSSink:kmssink0: sync = false
/GstPipeline:pipeline0/GstVideoTestSrc:videotestsrc0.GstPad:src: caps = video/x-raw, format=(string)RGB, width=(int)50, height=(int)50, framerate=(fraction)60/1, multiview-mode=(string)mono, pixel-aspect-ratio=(fraction)16/15, interlace-mode=(string)progressive
/GstPipeline:pipeline0/GstCapsFilter:capsfilter0.GstPad:src: caps = video/x-raw, format=(string)RGB, width=(int)50, height=(int)50, framerate=(fraction)60/1, multiview-mode=(string)mono, pixel-aspect-ratio=(fraction)16/15, interlace-mode=(string)progressive
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0.GstGhostPad:sink.GstProxyPad:proxypad0: caps = video/x-raw, format=(string)RGB, width=(int)50, height=(int)50, framerate=(fraction)60/1, multiview-mode=(string)mono, pixel-aspect-ratio=(fraction)16/15, interlace-mode=(string)progressive
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0/GstKMSSink:kmssink0.GstPad:sink: caps = video/x-raw, format=(string)RGB, width=(int)50, height=(int)50, framerate=(fraction)60/1, multiview-mode=(string)mono, pixel-aspect-ratio=(fraction)16/15, interlace-mode=(string)progressive
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0.GstGhostPad:sink: caps = video/x-raw, format=(string)RGB, width=(int)50, height=(int)50, framerate=(fraction)60/1, multiview-mode=(string)mono, pixel-aspect-ratio=(fraction)16/15, interlace-mode=(string)progressive
/GstPipeline:pipeline0/GstCapsFilter:capsfilter0.GstPad:sink: caps = video/x-raw, format=(string)RGB, width=(int)50, height=(int)50, framerate=(fraction)60/1, multiview-mode=(string)mono, pixel-aspect-ratio=(fraction)16/15, interlace-mode=(string)progressive
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
Redistribute latency...
New clock: GstSystemClock
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0/GstKMSSink:kmssink0: sync = false
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0: last-message = rendered: 16, dropped: 0, current: 30.68, average: 30.68
/GstPipeline:pipeline0/GstFPSDisplaySink:fpsdisplaysink0: last-message = rendered: 32, dropped: 0, current: 30.05, average: 30.36
handling interrupt.:99.
Interrupt: Stopping pipeline ...
Execution ended after 0:00:01.497017765
Setting pipeline to NULL ...
Freeing pipeline ...

After the GStreamer pipeline terminates, the last displayed frame remains on the screen.
Enable the ALWAYS_ON_DISPLAY property to keep the display pipeline powered during suspend.
The property ID 42 corresponds to the ALWAYS_ON_DISPLAY CRTC property:

.. code-block:: console

root@am62lxx-evm:~# modetest -M tidss -w 42:ALWAYS_ON_DISPLAY:1 # 42 is the ALWAYS_ON_DISPLAY CRTC property ID

Configure the system to use s2idle suspend mode, which allows the display to remain powered:

.. code-block:: console

root@am62lxx-evm:~# echo s2idle > /sys/power/mem_sleep

Now the SoC can be suspended using the following command:

.. code-block:: console

root@am62lxx-evm:~# echo mem > /sys/power/state
[ 101.964352] PM: suspend entry (s2idle)
[ 101.968392] Filesystems sync: 0.000 seconds
[ 101.973713] Freezing user space processes
[ 101.980059] Freezing user space processes completed (elapsed 0.002 seconds)
[ 101.987068] OOM killer disabled.
[ 101.990296] Freezing remaining freezable tasks
[ 101.996139] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
[ 102.027260] k3_wkup_src_notify wkup-src-notify: wakeup source:0x10000, pin:0x6d, mode:0x8
[ 102.060012] am65-cpsw-nuss 8000000.ethernet: set new flow-id-base 96
[ 102.080175] am65-cpsw-nuss 8000000.ethernet eth0: PHY [8000f00.mdio:00] driver [TI DP83867] (irq=POLL)
[ 102.090380] am65-cpsw-nuss 8000000.ethernet eth0: configuring for phy/rgmii-rxid link mode
[ 102.112383] am65-cpsw-nuss 8000000.ethernet eth1: PHY [8000f00.mdio:01] driver [TI DP83867] (irq=POLL)
[ 102.122586] am65-cpsw-nuss 8000000.ethernet eth1: configuring for phy/rgmii-rxid link mode
[ 102.474090] OOM killer enabled.
[ 102.477363] Restarting tasks: Starting
[ 102.499994] Restarting tasks: Done
[ 102.503505] random: crng reseeded on system resumption
[ 102.509008] PM: suspend exit
root@am62lxx-evm:~#

Resuming from DSS plus Deep Sleep
=================================

After the system resumes from DSS plus Deep Sleep, the static frame continues to be displayed
from the FIFO. The display does **not** automatically transition back to dynamic content.
To return to normal display operation, you must manually disable the SELF_REFRESH and
ALWAYS_ON_DISPLAY properties:

.. code-block:: console

root@am62lxx-evm:~# modetest -M tidss -w 35:SELF_REFRESH:0 # Disable FIFO replay
root@am62lxx-evm:~# modetest -M tidss -w 42:ALWAYS_ON_DISPLAY:0 # Allow display pipeline to be powered off

Once these properties are disabled, the display subsystem returns to fetching framebuffers
from DDR and can display dynamic content normally. Any display manager or application can
then take control of the display again.

Memory Usage
************

The following table summarizes the usage of memory in different modes of
operation of the device.

+--------+-------------+----------------------+------------------+------------+-------------------+
| Domain | Memory | Boot Operation | Normal Operation | Deep Sleep | RTC Only + DDR |
+========+=============+======================+==================+============+===================+
| WKUP | TIFS SRAM | TIFS load (144 KB) | TIFS (144 KB) | TIFS | TIFS (144 KB) |
| | (196 KB) | + Sec ROM (20 KB) | | (144 KB) | |
| | | | | | SEC ROM (20 KB) |
| | | | | | |
| | | | | | TIFS_STUB (32 KB) |
+--------+-------------+----------------------+------------------+------------+-------------------+
| WKUP | WKUP PSRAM | Pub ROM (64 KB) | | A53 Stub, | Pub ROM (64 KB) |
| | (512 KB) | or (exclusively) | | TF-A Stub | |
| | | PreBL Stack & | | (64 KB) | |
| | | runtime data (64 KB) | | | |
+--------+-------------+----------------------+------------------+------------+-------------------+
| Main | MAIN MSRAM | PreBL (64 KB) | TIFS IPC (24 KB) | TIFS IPC | PreBL (64 KB) |
| | (96 KB) | DDR initialization | | (24 KB) | Non-destructive |
| | | | | | DDR initializtion |
| | | Pub ROM (8 KB) | | | |
| | | | | | TIFS IPC + |
| | | ROM IPC (8 KB) | | | ROM IPC (24 KB) |
| | | | | | |
| | | | | | Pub ROM (8 KB) |
+--------+-------------+----------------------+------------------+------------+-------------------+
| Main | DDR | Linux | Linux | Linux | Linux |
| | | | | | |
| | | TF-A | TF-A | TF-A | TF-A |
+--------+-------------+----------------------+------------------+------------+-------------------+
+--------+-------------+----------------------+------------------+-------------------------+-------------------+
| Domain | Memory | Boot Operation | Normal Operation | Deep Sleep / | RTC Only + DDR |
| | | | | DSS plus Deep Sleep | |
+========+=============+======================+==================+=========================+===================+
| WKUP | TIFS SRAM | TIFS load (144 KB) | TIFS (144 KB) | TIFS | TIFS (144 KB) |
| | (196 KB) | + Sec ROM (20 KB) | | (144 KB) | |
| | | | | | SEC ROM (20 KB) |
| | | | | | |
| | | | | | TIFS_STUB (32 KB) |
+--------+-------------+----------------------+------------------+-------------------------+-------------------+
| WKUP | WKUP PSRAM | Pub ROM (64 KB) | | A53 Stub, | Pub ROM (64 KB) |
| | (512 KB) | or (exclusively) | | TF-A Stub | |
| | | PreBL Stack & | | (64 KB) | |
| | | runtime data (64 KB) | | | |
+--------+-------------+----------------------+------------------+-------------------------+-------------------+
| Main | MAIN MSRAM | PreBL (64 KB) | TIFS IPC (24 KB) | TIFS IPC | PreBL (64 KB) |
| | (96 KB) | DDR initialization | | (24 KB) | Non-destructive |
| | | | | | DDR initializtion |
| | | Pub ROM (8 KB) | | | |
| | | | | | TIFS IPC + |
| | | ROM IPC (8 KB) | | | ROM IPC (24 KB) |
| | | | | | |
| | | | | | Pub ROM (8 KB) |
+--------+-------------+----------------------+------------------+-------------------------+-------------------+
| Main | DDR | Linux | Linux | Linux | Linux |
| | | | | | |
| | | TF-A | TF-A | TF-A | TF-A |
+--------+-------------+----------------------+------------------+-------------------------+-------------------+
1 change: 1 addition & 0 deletions source/linux/Foundational_Components/Power_Management/pm_overview.rst
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Expand Up @@ -72,3 +72,4 @@ supported by the Linux kernel.
#. RTC Only
#. RTC Only Plus DDR
#. Deep Sleep
#. DSS plus Deep Sleep
30 changes: 15 additions & 15 deletions source/linux/Foundational_Components/Power_Management/pm_wakeup_sources.rst
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Expand Up @@ -53,21 +53,21 @@ valid for given low power modes:

.. ifconfig:: CONFIG_part_variant in ('AM62LX')

+------------------------------------------------+------------+----------------+----------+
| Wakeup Source | Deep Sleep | RTC Only + DDR | RTC Only |
+================================================+============+================+==========+
| Real-Time Clock (RTC) | Yes | Yes | Yes |
+------------------------------------------------+------------+----------------+----------+
| WKUP GPIO | Yes | No | No |
+------------------------------------------------+------------+----------------+----------+
| Main I/O Daisy Chain (Main GPIO and Main UART) | Yes | No | No |
+------------------------------------------------+------------+----------------+----------+
| WKUP UART | Yes | No | No |
+------------------------------------------------+------------+----------------+----------+
| USB Wakeup | Yes | No | No |
+------------------------------------------------+------------+----------------+----------+
| RTC Ext Pin | Yes | Yes | Yes |
+------------------------------------------------+------------+----------------+----------+
+------------------------------------------------+---------------------+------------+----------------+----------+
| Wakeup Source | DSS plus Deep Sleep | Deep Sleep | RTC Only + DDR | RTC Only |
+================================================+=====================+============+================+==========+
| Real-Time Clock (RTC) | Yes | Yes | Yes | Yes |
+------------------------------------------------+---------------------+------------+----------------+----------+
| WKUP GPIO | Yes | Yes | No | No |
+------------------------------------------------+---------------------+------------+----------------+----------+
| Main I/O Daisy Chain (Main GPIO and Main UART) | Yes | Yes | No | No |
+------------------------------------------------+---------------------+------------+----------------+----------+
| WKUP UART | Yes | Yes | No | No |
+------------------------------------------------+---------------------+------------+----------------+----------+
| USB Wakeup | Yes | Yes | No | No |
+------------------------------------------------+---------------------+------------+----------------+----------+
| RTC Ext Pin | Yes | Yes | Yes | Yes |
+------------------------------------------------+---------------------+------------+----------------+----------+

*********************
Real-Time Clock (RTC)
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