AM5728: PCIe PHY link issue

allen.zhang

Part Number: AM5728

Hello,

I want to implement communication between AM5728 and fpga using pcie: the arm is configured in RC mode, and fpga is used as the endpoint device.

I have only just begun to contact pcie these days. The SDK documentation doesn't describe much about Pcie Root Complex, and it is based on keystone.

Sdk document link: http://software-dl.ti.com/processor-sdk-linux/esd/docs/05_02_00_10/linux/Foundational_Components_Kernel_Drivers.html#pcie-root-complex

Here is my environment:

platform : am5728-idk

sdk : processor-sdk-linux 05.02.00.10

rootfs : tisdk-rootfs-image-am57xx-evm

devicetree : am572x-idk-lcd-osd101t2587.dts

&pcie1_rc {
status = "okay";
gpios = <&gpio3 23 GPIO_ACTIVE_HIGH>;
};

&pcie1_ep {
gpios = <&gpio3 23 GPIO_ACTIVE_HIGH>;
};

kernel config : am57xx_evm_defconfig

I can't find the pci device corresponding to fpga using lscpi command.

This is the kernel boot log:

Found that pcie waited for link up time out: "phy link never came up".How to fix it?

There are 3 modprobe errors in the log. Are there any effects?

Assuming the fpga endpoint device is detected, how do I communicate? Are there any examples for reference? .

Best Regards,

Allen

over 5 years ago

0 Bin Liu over 5 years ago

TI__Guru**** 171821 points

Hi Allen,

I didn't see such modprobe errors before, but assume they indicate some issues in PCIe.

How the PERST signal on the PCIe BUS (pin #11) is implemented on your board?

The AM572x IDK board uses a GPIO for this PCIe PERST signal, and it is defined in pcie1_rc node in am572x-idk-common.dtsi. Then the Linux PCIe driver will use the GPIO to reset the PCIe bus before scanning it.

0 allen.zhang over 5 years ago in reply to Bin Liu

Intellectual 365 points

Hi Bin,

The board I use is am572x-idk. As you described, it uses gpio for PCIe PERST.

I was able to capture this reset signal on the endpoint device (fpga).

Best Regards,

Allen

0 Bin Liu over 5 years ago in reply to allen.zhang

TI__Guru**** 171821 points

Hi Allen,

Sorry I missed the point that you use the IDK evm, then the PCIe RC hardware and software should be ready to enumerate any EP attached to the bus. Please ensure the FPGA EP is fully powered up and ready to be scanned before Linux boots up on AM5728.

0 allen.zhang over 5 years ago in reply to Bin Liu

Intellectual 365 points

Hi Bin,

Yes, fpga is fully powered up before linux boots . I checked the LTSSM STATE of ARM and fpga, both are in the state of POLL_ACTIVE.

Best Regards,
Allen

0 Bin Liu over 5 years ago in reply to allen.zhang

TI__Guru**** 171821 points

Hi Allen,

Did you change anything in the kernel config or device tree other than using tisdk_am57xx-evm_defconfig compiling the kernel?

Can the FPGA be enumerated on other platform for example a PC?

0 allen.zhang over 5 years ago in reply to Bin Liu

Intellectual 365 points

Hi Bin,

I using tisdk_am57xx-evm_defconfig and am572x-idk-lcd-osd101t2587.dts compiling the kernel and dtb, without any change.

I just connected fpga to a PC and it was not enumerated. I'm looking for the reason now. Thanks for your suggestion.

Best Regards,
Allen

0 Bin Liu over 5 years ago in reply to allen.zhang

TI__Guru**** 171821 points

Hi Allen,

Thanks for the update. I am closing this thread for now. Once you find the root cause and need assistance on AM57 side, please just post a reply below (or create a new thread if the thread has locked due to time-out). thanks.

0 allen.zhang over 5 years ago in reply to Bin Liu

Intellectual 365 points

Hi Bin,

On my custom board, fpga is always loaded after kernel boot.However the pcie driver does not seem to compile as a module, it can only be compiled into the kernel, so fpga cannot be detected.Does pcie support Hotplug?

Best Regards,

Allen

0 Bin Liu over 5 years ago in reply to allen.zhang

TI__Guru**** 171821 points

Hi Allen,

No, PCIe hotplug is not supported.

0 allen.zhang over 5 years ago in reply to Bin Liu

Intellectual 365 points

Hi Bin,

Sorry for late update.
Due to the following reasons, PCI cannot be properly initialized and enumerated:
1. AM57XX_PCIE_REF_CLKP / N on my board is provided by pll, which is initialized after linux boot up.
2.Fpga is loaded after linux boot up.

Is there any way to do pcie's probe or enumeration process after linux boot up?
Is it possible to compile pcie as a module? Including its dependent modules.
Or implement a pcie enumeration interface for user?

If there is no way, I can only load fpga and initialize pll in the boot, although this is not a good way.

Best Regards,

Allen

0 Bin Liu over 5 years ago in reply to allen.zhang

TI__Guru**** 171821 points

Hi Allen,

Kernel doesn't allow any PCIe driver to be built as module. And I am not aware of any way to manualy delay the PCIe enumeration process. But please try the rescan method mentioned in the e2e thread linked below.

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AM5728: PCIe PHY link issue