PCIE_NVME.md

NVMe Timeout Issue

Currently the SSD NVMe is not detected at boot by default due to a Kernel bug:

[    3.150189] rockchip-pcie f8000000.pcie: PCIe link training gen1 timeout!

This is caused by too short PCI-E link training time:

	/* 500ms timeout value should be enough for Gen1/2 training */
	err = readl_poll_timeout(rockchip->apb_base + PCIE_CLIENT_BASIC_STATUS1,
				 status, PCIE_LINK_UP(status), 20,
				 500 * USEC_PER_MSEC);
	if (err) {
		dev_err(dev, "PCIe link training gen1 timeout!\n");
		goto err_power_off_phy;
	}

https://github.com/torvalds/linux/blob/4b0986a3/drivers/pci/controller/pcie-rockchip-host.c#L330-L339

This causes system to not be bootable without patching or special configuration.

Kernel Configuration

To make the NVMe SSD be detected you will need to compile some modules directly into the kernel:

PHY_ROCKCHIP_PCIE y
PCIE_ROCKCHIP_HOST y

To do this in NixOS configuration use:

{
  boot.kernelPackages = pkgs.linuxPackages_5_18;
  boot.kernelPatches = [{
    name = "pcie-rockchip-config.patch";
    patch = null;
    extraConfig = ''
      PHY_ROCKCHIP_PCIE y
      PCIE_ROCKCHIP_HOST y
    '';
  }];
}

It's a good idea to also lock the kernel verison to avoid rebuilds.

Kernel Patch

The other way is to include the patch that adds support for the pcie_rk_bus_scan_delay kernel parameter:

• https://github.com/ayufan-rock64/linux-mainline-kernel/commit/005d53f6519887c24d73e8542be1d258be633169

But that patch is only for 5.9 version of Linux Kernel.