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fix: Update the how_to_check_device_tree_info guide
Fix the examples in this guide by implementing the following: - Switch from xxd to hexdump since xxd is no longer packaged in fs - Add examples and logs for am62* devices - Update code blocks to .. code-block:: console format - Make the document more generic by using <machine> for device in logs Signed-off-by: Judith Mendez <[email protected]>
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‎source/linux/How_to_Guides/FAQ/How_to_Check_Device_Tree_Info.rst‎

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@@ -9,81 +9,152 @@ using the entries in /proc/device-tree.
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In the command prompt of Linux, you should see something similar to the
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following in the /proc/device-tree directory:
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::
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root@j721e-evm:~# ls /proc/device-tree/
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#address-cells firmware l3-cache0
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#size-cells fixedregulator-evm12v0 main_r5fss_cpsw9g_virt_mac0
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__symbols__ fixedregulator-sd memory@80000000
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aliases fixedregulator-vsys3v3 model
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chosen fixedregulator-vsys5v0 name
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compatible gpio-keys pmu
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connector interconnect@100000 reserved-memory
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cpus interrupt-parent serial-number
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dma_buf_phys ion sound@0
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dummy-panel l2-cache0 timer-cl0-cpu0
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.. code-block:: console
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root@j721e-evm:~# ls /proc/device-tree/
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#address-cells firmware l3-cache0
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#size-cells fixedregulator-evm12v0 main_r5fss_cpsw9g_virt_mac0
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__symbols__ fixedregulator-sd memory@80000000
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aliases fixedregulator-vsys3v3 model
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chosen fixedregulator-vsys5v0 name
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compatible gpio-keys pmu
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connector interconnect@100000 reserved-memory
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cpus interrupt-parent serial-number
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dma_buf_phys ion sound@0
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dummy-panel l2-cache0 timer-cl0-cpu0
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Following are some typical usages you might need:
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- Let's say you don't know the exact path of the device tree entry you are
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trying to check. There is a __symbol__ directory in /proc/device-tree, which
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is very helpful in such cases. It has an entry for each symbol label in the
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device tree. You can find the exact path for that symbol by running ``cat``
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command on that entry. Following is an example demonstrating the use:
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Let's say you don't know the exact path of the device tree entry you are
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trying to check. There is a :file:`__symbols__` directory in /proc/device-tree, which
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is very helpful in such cases. It has an entry for each symbol label in the
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device tree. You can find the exact path for that symbol by running :command:`cat`
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command on that entry. Following is an example demonstrating the use:
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::
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.. ifconfig:: CONFIG_part_variant not in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')
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root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_i2c0
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/interconnect@100000/i2c@2000000
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.. code-block:: console
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root@j721e-evm:~# ls /proc/device-tree/interconnect@100000/i2c@2000000/
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#address-cells clock-names gpio@20 name pinctrl-names
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#size-cells clocks gpio@22 phandle power-domains
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clock-frequency compatible interrupts pinctrl-0 reg
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root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_i2c0
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/interconnect@100000/i2c@2000000
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- You can check the value of a device tree entry using ``cat`` command if it is a
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string. But if the value is an integer or some numeric data, you will have to
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run the ``xxd`` command instead of ``cat``, to get output in a readable format.
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Following is an example demonstrating the use:
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root@j721e-evm:~# ls /proc/device-tree/interconnect@100000/i2c@2000000/
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#address-cells clock-names gpio@20 name pinctrl-names
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#size-cells clocks gpio@22 phandle power-domains
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clock-frequency compatible interrupts pinctrl-0 reg
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::
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.. ifconfig:: CONFIG_part_variant in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')
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# Example for a string value
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root@j721e-evm:~# cat /proc/device-tree/interconnect@100000/i2c@2000000/compatible
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ti,j721e-i2cti,omap4-i2c
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.. code-block:: console
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# Example for an integer value
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root@j721e-evm:~# xxd -g4 /proc/device-tree/interconnect@100000/i2c@2000000/clock-frequency
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00000000: 00061a80 ....
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root@am62xx-evm:~# cat /proc/device-tree/__symbols__/main_i2c0
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/bus@f0000/i2c@20000000
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# The above value is in hexadecimal. You can calculate it's value in decimal by using following command
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root@j721e-evm:~# echo $((0x00061a80))
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400000
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root@am62xx-evm:~# ls /proc/device-tree/bus@f0000/i2c@20000000/
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'#address-cells' clock-names eeprom@51 phandle power-domains tps6598x@3f
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'#size-cells' clocks interrupts pinctrl-0 reg
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clock-frequency compatible name pinctrl-names status
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- One common scenario of a device tree change is tweaking the memory for
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remoteproc processors like R5F. You can check if it got updated correctly, by
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running a command similar to following for the specific processor core.
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You can check the value of a device tree entry using :command:`cat` command if it is a
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string. But if the value is an integer or some numeric data, you will have to
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run the :command:`hexdump` command instead to get output in a readable format.
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Following is an example demonstrating the use:
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::
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.. ifconfig:: CONFIG_part_variant not in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')
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# Finding symbols for R5Fs
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root@j721e-evm:~# ls /proc/device-tree/__symbols__/main_r5fss*
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/proc/device-tree/__symbols__/main_r5fss0 /proc/device-tree/__symbols__/main_r5fss0_core1_dma_memory_region /proc/device-tree/__symbols__/main_r5fss1_core0_memory_region
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/proc/device-tree/__symbols__/main_r5fss0_core0 /proc/device-tree/__symbols__/main_r5fss0_core1_memory_region /proc/device-tree/__symbols__/main_r5fss1_core1
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/proc/device-tree/__symbols__/main_r5fss0_core0_dma_memory_region /proc/device-tree/__symbols__/main_r5fss1 /proc/device-tree/__symbols__/main_r5fss1_core1_dma_memory_region
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/proc/device-tree/__symbols__/main_r5fss0_core0_memory_region /proc/device-tree/__symbols__/main_r5fss1_core0 /proc/device-tree/__symbols__/main_r5fss1_core1_memory_region
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/proc/device-tree/__symbols__/main_r5fss0_core1 /proc/device-tree/__symbols__/main_r5fss1_core0_dma_memory_region
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.. code-block:: console
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# Finding location from the symbols
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root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_r5fss0_core0_memory_region
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/reserved-memory/r5f-memory@a2100000
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# Example for a string value
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root@j721e-evm:~# cat /proc/device-tree/interconnect@100000/i2c@2000000/compatible
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ti,j721e-i2cti,omap4-i2c
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root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_r5fss0_core0_dma_memory_region
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/reserved-memory/r5f-dma-memory@a2000000
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# Example for an integer value where the first column represents input offsets
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root@j721e-evm:~# hexdump -C /proc/device-tree/interconnect@100000/i2c@2000000/clock-frequency
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00000000 00 06 1a 80 |....|
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00000004
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# Checking the values
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root@j721e-evm:~# xxd -g4 /proc/device-tree/reserved-memory/r5f-memory@a2100000/reg
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00000000: 00000000 a2100000 00000000 01f00000 ................
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# The above value is in hexadecimal. You can calculate it's value in decimal by using following command
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root@j721e-evm:~# echo $((0x00061a80))
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400000
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root@j721e-evm:~# xxd -g4 /proc/device-tree/reserved-memory/r5f-dma-memory@a2000000/reg
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00000000: 00000000 a2000000 00000000 00100000 ................
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.. ifconfig:: CONFIG_part_variant in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')
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.. code-block:: console
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# Example for a string value
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root@am62xx-evm:~# cat /proc/device-tree/bus@f0000/i2c@20000000/compatible
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ti,am64-i2cti,omap4-i2c
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# Example for an integer value where the first column represents input offsets
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root@am62xx-evm:~# hexdump -C /proc/device-tree/bus@f0000/i2c@20000000/clock-frequency
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00000000 00 06 1a 80 |....|
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00000004
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# The above value is in hexadecimal. You can calculate it's value in decimal by using following command
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root@am62xx-evm:~# echo $((0x00061a80))
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400000
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One common scenario of a device tree change is tweaking the memory for
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remoteproc processors like R5F. You can check if it got updated correctly, by
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running a command similar to following for the specific processor core.
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.. ifconfig:: CONFIG_part_variant not in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')
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.. code-block:: console
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# Finding symbols for R5Fs
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root@j721e-evm:~# ls /proc/device-tree/__symbols__/main_r5fss*
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/proc/device-tree/__symbols__/main_r5fss0 /proc/device-tree/__symbols__/main_r5fss0_core1_dma_memory_region /proc/device-tree/__symbols__/main_r5fss1_core0_memory_region
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/proc/device-tree/__symbols__/main_r5fss0_core0 /proc/device-tree/__symbols__/main_r5fss0_core1_memory_region /proc/device-tree/__symbols__/main_r5fss1_core1
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/proc/device-tree/__symbols__/main_r5fss0_core0_dma_memory_region /proc/device-tree/__symbols__/main_r5fss1 /proc/device-tree/__symbols__/main_r5fss1_core1_dma_memory_region
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/proc/device-tree/__symbols__/main_r5fss0_core0_memory_region /proc/device-tree/__symbols__/main_r5fss1_core0 /proc/device-tree/__symbols__/main_r5fss1_core1_memory_region
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/proc/device-tree/__symbols__/main_r5fss0_core1 /proc/device-tree/__symbols__/main_r5fss1_core0_dma_memory_region
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# Finding location from the symbols
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root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_r5fss0_core0_memory_region
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/reserved-memory/r5f-memory@a2100000
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root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_r5fss0_core0_dma_memory_region
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/reserved-memory/r5f-dma-memory@a2000000
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# Checking the values
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root@j721e-evm:~# hexdump -C /proc/device-tree/reserved-memory/r5f-memory@a2100000/reg
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00000000: 00000000 a2100000 00000000 01<address>0 ................
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root@j721e-evm:~# hexdump -C /proc/device-tree/reserved-memory/r5f-dma-memory@a2000000/reg
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00000000: 00000000 a2000000 00000000 00100000 ................
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.. ifconfig:: CONFIG_part_variant in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')
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.. code-block:: console
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# Finding symbols for remote cores
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root@am62xx-evm:~# ls /proc/device-tree/__symbols__/ | grep "r5f"; ls /proc/device-tree/__symbols__/ | grep "m4f"; ls /proc/device-tree/__symbols__/ | grep "c7x";
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wkup_r5fss0
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wkup_r5fss0_core0
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wkup_r5fss0_core0_dma_memory_region
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wkup_r5fss0_core0_memory_region
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mcu_m4fss
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mcu_m4fss_dma_memory_region
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mcu_m4fss_memory_region
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# Finding location from the symbols
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root@am62xx-evm:~# cat /proc/device-tree/__symbols__/mcu_m4fss_memory_region
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/reserved-memory/m4f-memory@9cc00000
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root@am62xx-evm:~# cat /proc/device-tree/__symbols__/mcu_m4fss_dma_memory_region
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/reserved-memory/m4f-dma-memory@9cb00000
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# Checking the values
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root@am62xx-evm:~# hexdump -C /proc/device-tree/reserved-memory/m4f-memory@9cc00000/reg
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00000000 00 00 00 00 9c c0 00 00 00 00 00 00 00 e0 00 00 |................|
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00000010
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root@am62xx-evm:~# hexdump -C /proc/device-tree/reserved-memory/m4f-dma-memory@9cb00000/reg
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00000000 00 00 00 00 9c b0 00 00 00 00 00 00 00 10 00 00 |................|
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00000010
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.. warning::
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Before tweaking the memory for remote processors, please verify that the memory
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can be modified since some remote processors can be running firmware like DM firmware.

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