PROCESSOR-SDK-J721E: PCIe setup Initial Questions for J721E EVM with TDA4VMx/DRA829Vx SoM

Hi Michelle,

Here are some clarifications on the software-side for questions 2, 3 and 4.

2. J721E is another common name used for TDA4VM/DRA829 SoCs. The Linux dts files all follow this name. So, please follow the steps referring to J721E or J7ES from the SDK documentation.

3. Do you know which version of the J721E EVM you have? Please refer to the J721E EVM Hardware Setup section of the SDK documentation to identify your EVM version. The following are the dtbs used:

    Beta EVM: k3-j721e-common-proc-board.dtb

    Alpha EVM: k3-j721e-proc-board-tps65917.dtb

The steps listed under 7.x SDK (5.4 kernel) should apply for 8.x SDK (5.10 kernel as well). The Alpha EVM dts file includes the Beta EVM dts file, so changes in k3-j721e-common-proc-board.dts file will be reflected in both dtbs.

4. The config_type refers to the interface you want to use for doing the kernel configuration. The Linux kernel provides couple of interfaces for this like menuconfig, xconfig, gconfig etc. I recommend you to stick with "menuconfig", the most common usage. 

You can browse and select the different configs under the appropriate menuitem. PCI options all are under Device Drivers->PCI Support.

The J721E specific options are under Device Drivers->PCI Support->PCI Controller Drivers->Cadence PCIe controllers support

Press the backslash key to search for different CONFIG symbols. (/)

regards

Suman

Hi Suman,

Thanks for your response.

To double check, you said:

Suman Anna said:

2. J721E is another common name used for TDA4VM/DRA829 SoCs. The Linux dts files all follow this name. So, please follow the steps referring to J721E or J7ES from the SDK documentation.

However, the dts files are named as dra7-evm, dra72-evm, am572x-idk, am65x-evm, and am65x-idk. These don't contain J721E or J7ES, can you clarify which one I should be downloading? And is the directory I should be calling the diff --git command <SDK INSTALL DIR>/board-support/linux-5.10.41+gitAUTOINC+4c2eade9f7-g4c2eade9f7?

In regards to your response to #4:

Suman Anna said:

4. The config_type refers to the interface you want to use for doing the kernel configuration. The Linux kernel provides couple of interfaces for this like menuconfig, xconfig, gconfig etc. I recommend you to stick with "menuconfig", the most common usage. 

I called the command "make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu- menuconfig" in the directory <SDK INSTALL DIR>/board-support/linux-5.10.41+gitAUTOINC+4c2eade9f7-g4c2eade9f7. An error came up, saying "scripts/Kconfig.include:39: compiler 'aarch64-none-linux-gnu-gcc' not found".

I followed the steps in the Linux SDK here  and downloaded the GCC tools from the links in the table and extracted them in my Downloads folder. However, how do I install these tools into the appropriate directory? My understanding was that we can source the environment setup script to have everything set up, but when reading section 3.2.1.3 Preparing to Build, it says to: "that you do NOT source the environment-setup file included with the toolchain when building the kernel. Doing so will cause the compilation of host side components within the kernel tree to fail."

This is my first time building/configuring the Linux Kernel, so any help will be appreciated. Thanks!

Hi Michelle,

Also, w.r.t question #1, you need cross over cables. RX of one EVM should be connected to TX of other EVM. So, you would need the -CX versions of the cables.

regards

Suman

Hi Suman,

Thank you, I will try the suggestions and follow up if I run into other questions.

As for the cables, is there any way/ modification to use none-cross over cables instead of buying the CX version? Thanks.

Hi Michelle,

I don't think there are any workarounds, since the PCIe pins and connector layout is the same on both boards, and we need the Tx and Rx to be swapped.

regards

Suman

Hi Suman,

Thank you, we will address the cable issue.

As for the patches, based on information I gathered from the Internet, the steps for creating a patch file and applying said patch is as follows? Please correct any wrong steps.

1. Create a patch file (with extension .patch). I made it in my Downloads folder and named it pcie_ep_patchfile.patch with the following content (from Linux SDK):

@@ -813,6 +813,7 @@
        phys = <&serdes0_pcie_link>;
        phy-names = "pcie_phy";
        num-lanes = <1>;
+       status = "disabled";
 }; &pcie1_rc {
@@ -833,7 +834,6 @@
        phys = <&serdes0_pcie_link>;
        phy-names = "pcie_phy";
        num-lanes = <1>;
-       status = "disabled";
 }; &pcie1_ep {

2. 

patch -u arch/arm64/boot/dts/ti/k3-j721e-common-proc-board.dts -i /home/user/Downloads/pcie_ep_patchfile.patch

3. Double check the patch is applied using 

git diff arch/arm64/boot/dts/ti/k3-j721e-common-proc-board.dts

Hi Michelle,

Yeah, above steps are ok, that's manually creating a patch file but can be prone to some issues. You need not create a patch file and then apply it. You could have just directly modified the dts files as well based on the + (addition) and - (deletion) from the reference.

The default dtb has the end-point node disabled. And the modifications disable the root-complex node and enable the end-point node. This modified dtb is to be used only on one board while the other board will continue to use the unmodified dtb.

regards

Suman