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Problems with APU2 when using Mini PCI-Express Dual Gigabit Ethernet Controller Card

Problems

  1. When Ethernet Controller Card is placed in mPCIe1 slot (J14) placed extension cards is recognized by OS but standard Ethernet output placed on APU2 board can't receive correct IP adress. So it doesn't work correct.

  2. When Ethernet Controller Card is placed in mPCIe2 slot (J13) 2 additional Ethernet controller are not visible in OS. Standard Ethernet output placed on APU2 board works well.

Device detection has been checked using ip a, lspci and dmesg. The results are shown in the table below.

    +-----+-----------------------------+
    | dev |          visibility         |
    +-----+--------------+--------------+
    | eth | mPCIe1 (J14) | mPCIe2 (J13) |
    +-----+--------------+--------------+
    |  0  |     yes      |     yes      |
    |  1  |     yes      |     yes      |
    |  2  |     yes      |     yes      |
    |  3  |     yes      |     no       |
    |  4  |     yes      |     no       |
    +--------------------+--------------+

Solution of the problems

Changing the value from 0xA to 0xF of the part of variable named data (showed under the following line) fixed the problems described in this file. This modification enables the clock regardless of the CLKREQ line state.

Mini PCI-Express Dual Gigabit Ethernet Controller Card elements

On a board are located PCI bridge ASMedia Technology Inc. Device 1182 and 2 Ethernet controllers Realtek Semiconductor Co., Ltd. RTL8111/8168/8411.

Booting lags

When Ethernet Controller is placed in the mPCIe1 slot (J14) and booting is at network devices setup time occurs long lag. In this case eth0 device can not get correct IP. After this next booting processes take same normal time. The reason may be multiple failed attempts to obtain an IP address. That problem doesn't exist for the mPCIe2 slot (J13).

Reason of that was time out value for DHCP client set to few minutes. After disabling DHCP client for eth0 interface booting lag doesn't occurs. Mentioned booting lag is not a bug.

Boot logs comparison

Level of the detail of booting logs was set at 6:DEBUG.

The full list varies between logs is placed at the end file.

The most suspicious difference in logs is placed below.

For mPCIe2:

    PCI: Static device PCI: 00:02.5 not found, disabling it.
For mPCIe1:

    PCI: 00:02.5 subordinate bus PCI Express
    PCI: 00:02.5 [1022/1439] enabled

This suggests a problem with device recognition when Ethernet Controller is placed in the mPCIe1 slot (J14). The reason for this can be concurent access of devices or incorrectly configured interrupt system.

Surrounding the log of the case when Ethernet Controller is placed in the mPCIe1 slot (J14).

    scan_bus: scanning of bus CPU_CLUSTER: 0 took 15987 usecs
    PCI: pci_scan_bus for bus 00
    PCI: 00:00.0 [1022/1566] enabled
    PCI: 00:02.0 [1022/156b] enabled
    PCI: Static device PCI: 00:02.1 not found, disabling it.
    PCI: 00:02.2 subordinate bus PCI Express
    PCI: 00:02.2 [1022/1439] enabled
    PCI: 00:02.3 subordinate bus PCI Express
    PCI: 00:02.3 [1022/1439] enabled
    PCI: 00:02.4 subordinate bus PCI Express
    PCI: 00:02.4 [1022/1439] enabled
    PCI: Static device PCI: 00:02.5 not found, disabling it.
    PCI: 00:08.0 [1022/1537] enabled
    hudson_enable()
    PCI: 00:10.0 [1022/7814] enabled
    hudson_enable()

Situation occurs at the moment when PCI bus is being scanned.

Checked potencial reasons

Several possible reasons for problems have been checked, but the problems continued.

  1. Tried to modify apu2/PlatformGnbPcie.c file like below.

        -PCIE_ENGINE_DATA_INITIALIZER (PciePortEngine, 4, 7),
    +PCIE_ENGINE_DATA_INITIALIZER (PciePortEngine, 4, 4),

    After modification system worked as before. The problems still occur.

  2. Measured voltages at CLKREQ4#and PE4RST# pins. All the time there was occurring high states for listed pins.

    Voltage at CLKREQ4# was about 0.02 V lower than expansion Ethernet controller card power supply voltage and voltage at PE4RST# was about 0.02 V higher than Ethernet controller card power supply voltage. The difference can be considered a measurement error.

Diff files from boot logs

Full diff files from APU2 boot logs between Ethernet Controller placed in the mPCIe1 slot (J14) and it placed in mPCIe2 slot (J13):