Known hardware issues with your Developerbox

64-bit PCIe transactions

The current revision of SC2A11 contains PCIe bus integration logic that does not correctly split certain types of bus transaction. These transactions are commonly initiated to PCIe devices with on board RAM, such as graphics cards. It is possible for other types of device to be affected if their drivers explicitly initiate 64-bit transactions (thankfully a scan of the Linux kernel suggests such drivers are fairly uncommon).

The issue is deterministic and results in the system freezing either as soon as an affected PCIe card is initialized or when a specific feature of an affected PCIe card is used for the first time.

It is not possible to entirely workaround this issue but it can be partially mitigated in a variety of ways:

A firmware workaround is available. This will configure the virtualization hardware to prohibit certain types of memory mapping. The workaround is controlled using DSW3-2, and is enabled then the DIP switch is on.

The workaround has been tested heavily with the nVidia GT-710 graphics card found in the Developerbox kit. It allows an unmodified nouveau driver to run 3D accelerated programs.

The workaround is not sufficient to enable all GT-710 features. In particular hardware video decode acceleration does not work, although the workaround is sufficient to prevent a full system freeze (the video decoder application will crash but other applications are unaffected). Additionally there may be problems associated with the splash screen in some distros. Workarounds for splash screen problems are distro dependent, consult the list of third party operating systems for more information.

Finally, because the workaround is implemented using the virtualization hardware, deploying this workaround will automatically disable KVM support in the kernel.
A kernel patch can be applied. This implements the same workaround as the firmware workaround above but it does so without using the virtualization hardware which means KVM support will not be disabled. This approach requires you to patch and build the kernel yourself.

We recommend that #1 be used in order to complete the install process, it is then possible to transition to this workaround instead.
The nouveau driver can be disabled. When the nouveau driver is disabled the kernel will render graphics to the EFI framebuffer configured by the firmware. This reduces the graphics card to a dumb device that scans out from a fixed frame buffer. Depending on your distro, 3D operations will either by unavailable or emulated in software running the Cortex-A53 processors. In either case adopting a lightweight desktop environment with limited use of 3D hardware (e.g. LXDE, XFCE) is strongly recommended.

To deploy this workaround add the following to your kernel command line:
```
modprobe.blacklist=nouveau
```
It is possible to run Developerbox headless. If you wish to use your Developerbox as a build server or for some similar role, then you may prefer to remove the graphics card entirely. When the graphics card is removed all console activity (both EDK2 menus and the Linux console) will automatically switch from using the graphics card to using the debug UART. The debug UART is connected to the micro-USB socket behind the I/O shield on the back panel.

The automatic switching of the console means the system maintenance capabilities via the UART are equivalent to those available via the graphics card, and the power saved as a result of removing the graphics card is significant. For that reason we would recommend running Developerbox headless for edge or build server applications regardless of whether or not your board is impacted by this issue.

GT-710 display freeze

The GT-710 graphics card provided in the kit may occasionally freeze. This is a generic nouveau driver issue that affects many different kernel versions across both x86 and Arm platforms.

This issue is non-deterministic and the frequency of failure can vary from anywhere between a few minutes and several days.

It can be worked around by adding the following to your kernel command line.

nouveau.config=NvClkMode=auto

Detailed instructions on how to modify the kernel command line are distro dependent, consult the list of third party operating systems for more information.

Common software issues

DHCP failures and/or poor performance with on-board networking

Early versions of the kernel driver for the on-board networking card do not configure the interrupts correctly. This can result in DHCP failures and/or extremely poor performance when using the on-board networking. This is especially common in installers because they often configure networking in a subtly different way to the installed OS and also because they often do not upgrade the kernel as frequently as the underlying distro.

This is known to impact mainline v4.16(.0) kernels together with distro kernels that use backported drivers taken from this kernel.

It can be worked around by using an external network device during the install process. Both PCIe or USB network devices are suitable for this, although it is important to select a device that is already supported by your chosen operating system.

nouveau with 64k pages

The nouveau driver for the GT-710 graphics card included in the kit will not initialize successfully on systems with 64k pages.

This issue is deterministic and results in a freeze during boot.

It can be worked around either by rebuilding the kernel and switching to 4k pages or by disabling the nouveau driver. When the nouveau driver is disabled the kernel will render graphics to the EFI framebuffer configured by the firmware. This reduces the graphics card to a dumb device that scans out from a fixed frame buffer. Depending on your distro 3D operations will either by unavailable or emulated in software running the Cortex-A53 processors. In either case adopting a lightweight desktop environment with limited use of 3D hardware (e.g. LXDE, XFCE) is strongly recommended.

To disable the nouveau driver add the following to your kernel command line:

modprobe.blacklist=nouveau