Forcing TX2 PCIe bus to remain powered on

I found this discussion about keep the pcie bus powered on.

https://devtalk.nvidia.com/default/topic/1049932/jetson-tx2/pcie-signal-connections-for-help/post/5356731/#5356731

Can you please provide the patch to enable power on for rel 32.3.1.

I have a custom carrier card with TX2i which does not recognize an Intel e1000e based NIC.
The pcie bus remains powered off, so we cannot use a scope to analyze the bus.

[ 1.237945] e1000e: Intel® PRO/1000 Network Driver - 3.2.6-k
[ 1.237950] e1000e: Copyright© 1999 - 2015 Intel Corporation.
[ 1.238009] igb: Intel® Gigabit Ethernet Network Driver - version 5.4.0-k
[ 1.238014] igb: Copyright © 2007-2014 Intel Corporation.
The eval board recognizes the NIC at this point and brings up the connections

[ 1.238049] igbvf: Intel® Gigabit Virtual Function Network Driver - version 2.4.0-k
[ 1.238053] igbvf: Copyright © 2009 - 2012 Intel Corporation.
[ 1.238092] Intel® 10GbE PCI Express Linux Network Driver - version 4.6.4
[ 1.238096] Copyright© 1999 - 2017 Intel Corporation.

I found this older comment that provides a patch for an unspecified release

https://devtalk.nvidia.com/default/topic/1038787/jetson-tx2/question-about-pcie-reset/post/5279969/#5279969

The R32.3.1 code is

list_for_each_entry_safe(port, tmp, &pcie->ports, list) {
                if (tegra_pcie_port_check_link(port)) {
                        port->status = 1;
                        port->ep_status = 1;
                        pcie->num_ports++;
                        tegra_pcie_update_lane_width(port);
                        tegra_pcie_update_pads2plle(port);
                        continue;
                }
                port->ep_status = 0;
                dev_info(pcie->dev, "link %u down, ignoring\n", port->index);
                tegra_pcie_port_disable(port);
        }

I have no knowledge of Linux PCI drivers, but would seem that the code should be changed so tegra_pcie_port_disable(port); is not called.

Are you saying that you are not able to apply the above patch?

I had two questions:

  1. Can you provide the patch referenced https://devtalk.nvidia.com/default/topic/1049932/jetson-tx2/pcie-signal-connections-for-help/post/5356731/#5356731
  2. Is my proposed patch the correct approach to have the pcei bus remain enabled?
    i.e. need information on how the drivers works.

Please use the below patch and recompile the kernel

diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
index 63c0e343d388..52c46b68981e 100644
--- a/drivers/pci/host/pci-tegra.c
+++ b/drivers/pci/host/pci-tegra.c
@@ -2194,7 +2194,7 @@ static bool tegra_pcie_port_check_link(struct tegra_pcie_port *port)
                tegra_pcie_port_reset(port);
        } while (--retries);
 
-       return false;
+       return true;
 }
 
 static void tegra_pcie_apply_sw_war(struct tegra_pcie_port *port,

Copy the updated Image to /boot/Image on the target. With this, you should be able to have root ports alive even without PCIe link up.