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Neha Malcom Francis
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feat(linux): Add documentation for dynamic DDR refresh rate change
Add driver documentation for kernel DDR driver and how to enable DDR temperature monitoring. Signed-off-by: Neha Malcom Francis <n-francis@ti.com>
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‎configs/AM62AX/AM62AX_linux_toc.txt‎

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@@ -55,6 +55,7 @@ linux/Foundational_Components_Kernel_Drivers
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linux/Foundational_Components/Kernel/Kernel_Drivers/Audio
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linux/Foundational_Components/Kernel/Kernel_Drivers/Camera/CSI2RX
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linux/Foundational_Components/Kernel/Kernel_Drivers/Crypto/SA2UL_OMAP
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linux/Foundational_Components/Kernel/Kernel_Drivers/DDR
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linux/Foundational_Components/Kernel/Kernel_Drivers/Display/DSS7
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linux/Foundational_Components/Kernel/Kernel_Drivers/DM-Timer
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linux/Foundational_Components/Kernel/Kernel_Drivers/EQEP

‎configs/AM62PX/AM62PX_linux_toc.txt‎

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linux/Foundational_Components/Kernel/Kernel_Drivers/Audio
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linux/Foundational_Components/Kernel/Kernel_Drivers/Camera/CSI2RX
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linux/Foundational_Components/Kernel/Kernel_Drivers/Crypto/SA2UL_OMAP
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linux/Foundational_Components/Kernel/Kernel_Drivers/DDR
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linux/Foundational_Components/Kernel/Kernel_Drivers/Display/DSS7
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linux/Foundational_Components/Kernel/Kernel_Drivers/DM-Timer
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linux/Foundational_Components/Kernel/Kernel_Drivers/EQEP

‎configs/AM62X/AM62X_linux_toc.txt‎

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linux/Foundational_Components/Kernel/Kernel_Drivers/Audio
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linux/Foundational_Components/Kernel/Kernel_Drivers/Camera/CSI2RX
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linux/Foundational_Components/Kernel/Kernel_Drivers/Crypto/SA2UL_OMAP
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linux/Foundational_Components/Kernel/Kernel_Drivers/DDR
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linux/Foundational_Components/Kernel/Kernel_Drivers/Display/DSS7
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linux/Foundational_Components/Kernel/Kernel_Drivers/DM-Timer
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linux/Foundational_Components/Kernel/Kernel_Drivers/EQEP

‎configs/AM64X/AM64X_linux_toc.txt‎

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linux/Foundational_Components_Kernel_Drivers
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linux/Foundational_Components/Kernel/Kernel_Drivers/ADC
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linux/Foundational_Components/Kernel/Kernel_Drivers/Crypto/SA2UL_OMAP
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linux/Foundational_Components/Kernel/Kernel_Drivers/DDR
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linux/Foundational_Components/Kernel/Kernel_Drivers/DM-Timer
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linux/Foundational_Components/Kernel/Kernel_Drivers/EQEP
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linux/Foundational_Components/Kernel/Kernel_Drivers/GPIO

‎configs/J7200/J7200_linux_toc.txt‎

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linux/Foundational_Components_Kernel_Drivers
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linux/Foundational_Components/Kernel/Kernel_Drivers/ADC
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linux/Foundational_Components/Kernel/Kernel_Drivers/Crypto/SA2UL_OMAP
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linux/Foundational_Components/Kernel/Kernel_Drivers/DDR
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linux/Foundational_Components/Kernel/Kernel_Drivers/DM-Timer
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linux/Foundational_Components/Kernel/Kernel_Drivers/MCAN
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linux/Foundational_Components/Kernel/Kernel_Drivers/GPIO

‎configs/J721E/J721E_linux_toc.txt‎

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linux/Foundational_Components/Kernel/Kernel_Drivers/Audio
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linux/Foundational_Components/Kernel/Kernel_Drivers/Camera/CSI2RX
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linux/Foundational_Components/Kernel/Kernel_Drivers/Crypto/SA2UL_OMAP
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linux/Foundational_Components/Kernel/Kernel_Drivers/DDR
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linux/Foundational_Components/Kernel/Kernel_Drivers/Display/DSS7
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linux/Foundational_Components/Kernel/Kernel_Drivers/DM-Timer
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linux/Foundational_Components/Kernel/Kernel_Drivers/GPIO

‎source/linux/Foundational_Components/Kernel/Kernel_Drivers/DDR.rst‎

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.. _K3-DDR-Driver:
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.. _ddr-driver:
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######
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K3 DDR
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######
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************
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Introduction
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************
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The K3 DDR driver provides management and monitoring capabilities for DDR memory
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subsystems on Texas Instruments K3 SoCs.
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The following is a list of supported K3 DDR driver features by device family:
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.. list-table:: K3 DDR Driver Feature Support
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:header-rows: 1
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* - Device Family
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- Temperature Monitoring
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* - J7200
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- Yes
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* - AM62x LP SK/ AM62Ax / AM62Px
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- Yes
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********************************
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Building and Enabling the Driver
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********************************
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.. rubric:: Kernel Configuration
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The following kernel configuration enables the K3 DDR driver:
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.. code-block:: kconfig
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CONFIG_K3_DDR_TEMP=y
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CONFIG_HWMON=y
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.. _ddr-temperature-monitoring-linux:
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************************************
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Using the DDR Temperature Monitoring
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************************************
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By default, the DDR subsystem keeps temperature polling turned off. For allowing
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the kernel driver to monitor temperature, the user must enable polling during
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DDR configuration and initialization at boot time.
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See :ref:`ddr-temperature-monitoring-uboot` in U-Boot documentation.
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The K3 DDR driver creates a hwmon device that provides temperature status
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information through sysfs. The driver registers as ``k3_ddr`` in the hwmon
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subsystem for temperature monitoring functionality.
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The driver reports temperature status according to LPDDR4 specification:
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.. list-table::
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:header-rows: 1
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:stub-columns: 1
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* - Value
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- Temperature Status
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* - 0
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- Low temperature
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* - 1
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- 4x refresh interval
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* - 2
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- 2x refresh interval
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* - 3
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- 1x refresh interval (nominal)
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* - 4
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- 0.5x refresh interval
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* - 5
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- 0.25x refresh interval
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* - 6
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- 0.25x refresh interval with derating
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* - 7
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- High temperature
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The hwmon device should now show up in the filesystem.
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.. code-block:: console
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root@evm:~# ls -l /sys/class/hwmon/
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hwmon0
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Check the current DDR temperature status:
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.. code-block:: console
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root@evm:~# cat /sys/class/hwmon/hwmon0/device/k3_ddr_temp_status
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1x refresh interval

‎source/linux/Foundational_Components/U-Boot/UG-DDRSS-J7.rst‎

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@@ -11,6 +11,8 @@ integrate these blocks in the device. The K3 DDRSS driver
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(:file:`drivers/ram/k3-ddrss/k3-ddrss.c`) runs during the R5 SPL stage and is
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responsible for initializing and configuring the DDR subsystem.
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.. _ddr-init:
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******************
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DDR Initialization
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******************
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selecting the software product as "DDR Configuration for \*" as well as the
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required device.
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.. _ddr-temperature-monitoring-uboot:
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**************************
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DDR Temperature Monitoring
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**************************
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For enabling temperature polling in the DDR subsystem the configuration DTSI
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(see :ref:`ddr-init`) must be regenerated after selecting 'Yes'
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for LPDDR > DDRSS x > Enable DRAM Temperature Polling and also changing the DRAM
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Timing Parameters as prompted by the tool.
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.. ifconfig:: CONFIG_part_variant in ('J7200', 'J721E')
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The kernel DDR driver utilizes this polling feature to provide base support for
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dynamic DDR refresh rate changes (see :ref:`ddr-temperature-monitoring-linux`)
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**********
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Inline ECC
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**********

‎source/linux/Foundational_Components/U-Boot/UG-DDRSS.rst‎

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(:file:`drivers/ram/k3-ddrss/k3-ddrss.c`) runs during the R5 SPL stage and is
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responsible for initializing and configuring the DDR subsystem.
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.. _ddr-init:
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******************
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DDR Initialization
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******************
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selecting the software product as "DDR Configuration for \*" as well as the
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required device.
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.. _ddr-temperature-monitoring-uboot:
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**************************
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Error Correction Code (ECC)
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DDR Temperature Monitoring
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**************************
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For enabling temperature polling in the DDR subsystem the configuration DTSI
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(see :ref:`ddr-init`) must be regenerated after selecting 'Yes'
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for LPDDR > DDRSS x > Enable DRAM Temperature Polling and also changing the DRAM
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Timing Parameters as prompted by the tool.
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The kernel DDR driver utilizes this polling feature to provide base support for
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dynamic DDR refresh rate changes (see :ref:`ddr-temperature-monitoring-linux`)
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***************************
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Error Correction Code (ECC)
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***************************
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For SDRAM data integrity, the DDRSS bridge supports inline ECC on the data
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written to or read from the SDRAM. ECC is stored together with the data so that
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a dedicated SDRAM device for ECC is not required. The 8-bit single error

‎source/linux/Foundational_Components_Kernel_Drivers.rst‎

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Foundational_Components/Kernel/Kernel_Drivers/MCAN
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Foundational_Components/Kernel/Kernel_Drivers/MCRC64
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Foundational_Components/Kernel/Kernel_Drivers/DCAN
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Foundational_Components/Kernel/Kernel_Drivers/DDR
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Foundational_Components/Kernel/Kernel_Drivers/Display/DSS
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Foundational_Components/Kernel/Kernel_Drivers/Display/DSS7
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Foundational_Components/Kernel/Kernel_Drivers/Display/LCDC

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