Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

fix: Update the how_to_check_device_tree_info guide #89

Merged
merged 1 commit into from
Dec 13, 2024
Merged

fix: Update the how_to_check_device_tree_info guide #89

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
191 changes: 131 additions & 60 deletions source/linux/How_to_Guides/FAQ/How_to_Check_Device_Tree_Info.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -9,81 +9,152 @@ using the entries in /proc/device-tree.
In the command prompt of Linux, you should see something similar to the
following in the /proc/device-tree directory:

::

root@j721e-evm:~# ls /proc/device-tree/
#address-cells firmware l3-cache0
#size-cells fixedregulator-evm12v0 main_r5fss_cpsw9g_virt_mac0
__symbols__ fixedregulator-sd memory@80000000
aliases fixedregulator-vsys3v3 model
chosen fixedregulator-vsys5v0 name
compatible gpio-keys pmu
connector interconnect@100000 reserved-memory
cpus interrupt-parent serial-number
dma_buf_phys ion sound@0
dummy-panel l2-cache0 timer-cl0-cpu0
.. code-block:: console

root@j721e-evm:~# ls /proc/device-tree/
#address-cells firmware l3-cache0
#size-cells fixedregulator-evm12v0 main_r5fss_cpsw9g_virt_mac0
__symbols__ fixedregulator-sd memory@80000000
aliases fixedregulator-vsys3v3 model
chosen fixedregulator-vsys5v0 name
compatible gpio-keys pmu
connector interconnect@100000 reserved-memory
cpus interrupt-parent serial-number
dma_buf_phys ion sound@0
dummy-panel l2-cache0 timer-cl0-cpu0

Following are some typical usages you might need:

- Let's say you don't know the exact path of the device tree entry you are
trying to check. There is a __symbol__ directory in /proc/device-tree, which
is very helpful in such cases. It has an entry for each symbol label in the
device tree. You can find the exact path for that symbol by running ``cat``
command on that entry. Following is an example demonstrating the use:
Let's say you don't know the exact path of the device tree entry you are
trying to check. There is a :file:`__symbols__` directory in /proc/device-tree, which
is very helpful in such cases. It has an entry for each symbol label in the
device tree. You can find the exact path for that symbol by running :command:`cat`
command on that entry. Following is an example demonstrating the use:

::
.. ifconfig:: CONFIG_part_variant not in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')

root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_i2c0
/interconnect@100000/i2c@2000000
.. code-block:: console

root@j721e-evm:~# ls /proc/device-tree/interconnect@100000/i2c@2000000/
#address-cells clock-names gpio@20 name pinctrl-names
#size-cells clocks gpio@22 phandle power-domains
clock-frequency compatible interrupts pinctrl-0 reg
root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_i2c0
/interconnect@100000/i2c@2000000

- You can check the value of a device tree entry using ``cat`` command if it is a
string. But if the value is an integer or some numeric data, you will have to
run the ``xxd`` command instead of ``cat``, to get output in a readable format.
Following is an example demonstrating the use:
root@j721e-evm:~# ls /proc/device-tree/interconnect@100000/i2c@2000000/
#address-cells clock-names gpio@20 name pinctrl-names
#size-cells clocks gpio@22 phandle power-domains
clock-frequency compatible interrupts pinctrl-0 reg

::
.. ifconfig:: CONFIG_part_variant in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')

# Example for a string value
root@j721e-evm:~# cat /proc/device-tree/interconnect@100000/i2c@2000000/compatible
ti,j721e-i2cti,omap4-i2c
.. code-block:: console

# Example for an integer value
root@j721e-evm:~# xxd -g4 /proc/device-tree/interconnect@100000/i2c@2000000/clock-frequency
00000000: 00061a80 ....
root@am62xx-evm:~# cat /proc/device-tree/__symbols__/main_i2c0
/bus@f0000/i2c@20000000

# The above value is in hexadecimal. You can calculate it's value in decimal by using following command
root@j721e-evm:~# echo $((0x00061a80))
400000
root@am62xx-evm:~# ls /proc/device-tree/bus@f0000/i2c@20000000/
'#address-cells' clock-names eeprom@51 phandle power-domains tps6598x@3f
'#size-cells' clocks interrupts pinctrl-0 reg
clock-frequency compatible name pinctrl-names status

- One common scenario of a device tree change is tweaking the memory for
remoteproc processors like R5F. You can check if it got updated correctly, by
running a command similar to following for the specific processor core.
You can check the value of a device tree entry using :command:`cat` command if it is a
string. But if the value is an integer or some numeric data, you will have to
run the :command:`hexdump` command instead to get output in a readable format.
Following is an example demonstrating the use:

::
.. ifconfig:: CONFIG_part_variant not in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')

# Finding symbols for R5Fs
root@j721e-evm:~# ls /proc/device-tree/__symbols__/main_r5fss*
/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
/proc/device-tree/__symbols__/main_r5fss0_core0 /proc/device-tree/__symbols__/main_r5fss0_core1_memory_region /proc/device-tree/__symbols__/main_r5fss1_core1
/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
/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
/proc/device-tree/__symbols__/main_r5fss0_core1 /proc/device-tree/__symbols__/main_r5fss1_core0_dma_memory_region
.. code-block:: console

# Finding location from the symbols
root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_r5fss0_core0_memory_region
/reserved-memory/r5f-memory@a2100000
# Example for a string value
root@j721e-evm:~# cat /proc/device-tree/interconnect@100000/i2c@2000000/compatible
ti,j721e-i2cti,omap4-i2c

root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_r5fss0_core0_dma_memory_region
/reserved-memory/r5f-dma-memory@a2000000
# Example for an integer value where the first column represents input offsets
root@j721e-evm:~# hexdump -C /proc/device-tree/interconnect@100000/i2c@2000000/clock-frequency
00000000 00 06 1a 80 |....|
00000004

# Checking the values
root@j721e-evm:~# xxd -g4 /proc/device-tree/reserved-memory/r5f-memory@a2100000/reg
00000000: 00000000 a2100000 00000000 01f00000 ................
# The above value is in hexadecimal. You can calculate it's value in decimal by using following command
root@j721e-evm:~# echo $((0x00061a80))
400000

root@j721e-evm:~# xxd -g4 /proc/device-tree/reserved-memory/r5f-dma-memory@a2000000/reg
00000000: 00000000 a2000000 00000000 00100000 ................
.. ifconfig:: CONFIG_part_variant in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')

.. code-block:: console

# Example for a string value
root@am62xx-evm:~# cat /proc/device-tree/bus@f0000/i2c@20000000/compatible
ti,am64-i2cti,omap4-i2c

# Example for an integer value where the first column represents input offsets
root@am62xx-evm:~# hexdump -C /proc/device-tree/bus@f0000/i2c@20000000/clock-frequency
00000000 00 06 1a 80 |....|
00000004

# The above value is in hexadecimal. You can calculate it's value in decimal by using following command
root@am62xx-evm:~# echo $((0x00061a80))
400000

One common scenario of a device tree change is tweaking the memory for
remoteproc processors like R5F. You can check if it got updated correctly, by
running a command similar to following for the specific processor core.

.. ifconfig:: CONFIG_part_variant not in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')

.. code-block:: console

# Finding symbols for R5Fs
root@j721e-evm:~# ls /proc/device-tree/__symbols__/main_r5fss*
/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
/proc/device-tree/__symbols__/main_r5fss0_core0 /proc/device-tree/__symbols__/main_r5fss0_core1_memory_region /proc/device-tree/__symbols__/main_r5fss1_core1
/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
/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
/proc/device-tree/__symbols__/main_r5fss0_core1 /proc/device-tree/__symbols__/main_r5fss1_core0_dma_memory_region

# Finding location from the symbols
root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_r5fss0_core0_memory_region
/reserved-memory/r5f-memory@a2100000

root@j721e-evm:~# cat /proc/device-tree/__symbols__/main_r5fss0_core0_dma_memory_region
/reserved-memory/r5f-dma-memory@a2000000

# Checking the values
root@j721e-evm:~# hexdump -C /proc/device-tree/reserved-memory/r5f-memory@a2100000/reg
00000000: 00000000 a2100000 00000000 01<address>0 ................

root@j721e-evm:~# hexdump -C /proc/device-tree/reserved-memory/r5f-dma-memory@a2000000/reg
00000000: 00000000 a2000000 00000000 00100000 ................

.. ifconfig:: CONFIG_part_variant in ('AM62X', 'AM62PX', 'AM62AX', 'AM64X', 'AM65X')

.. code-block:: console

# Finding symbols for remote cores
root@am62xx-evm:~# ls /proc/device-tree/__symbols__/ | grep "r5f"; ls /proc/device-tree/__symbols__/ | grep "m4f"; ls /proc/device-tree/__symbols__/ | grep "c7x";
wkup_r5fss0
wkup_r5fss0_core0
wkup_r5fss0_core0_dma_memory_region
wkup_r5fss0_core0_memory_region
mcu_m4fss
mcu_m4fss_dma_memory_region
mcu_m4fss_memory_region

# Finding location from the symbols
root@am62xx-evm:~# cat /proc/device-tree/__symbols__/mcu_m4fss_memory_region
/reserved-memory/m4f-memory@9cc00000

root@am62xx-evm:~# cat /proc/device-tree/__symbols__/mcu_m4fss_dma_memory_region
/reserved-memory/m4f-dma-memory@9cb00000

# Checking the values
root@am62xx-evm:~# hexdump -C /proc/device-tree/reserved-memory/m4f-memory@9cc00000/reg
00000000 00 00 00 00 9c c0 00 00 00 00 00 00 00 e0 00 00 |................|
00000010

root@am62xx-evm:~# hexdump -C /proc/device-tree/reserved-memory/m4f-dma-memory@9cb00000/reg
00000000 00 00 00 00 9c b0 00 00 00 00 00 00 00 10 00 00 |................|
00000010

.. warning::

Before tweaking the memory for remote processors, please verify that the memory
can be modified since some remote processors can be running firmware like DM firmware.
Loading