Lenovo Thinkpad T495

Lenovo Thinkpad T495 is a business notebook based on 2nd generation of AMD Ryzen™ processors with Radeon™ Vega graphics, supporting AMD FreeSync™, and delivering up to 14.9 hours of battery life.

Standard
Lenovo Thinkpad T495 specification:

Accessories
CPU and its features:

List of PCI devices:

List of USB devices:

Processor
Using with the   USE flag will have additional Processor family options made available:

or simply autodetecting the processor options by the compiler:

For more information see the wiki page on AMD Ryzen processors.

Firmware
In order for the graphics and wireless to work properly, it is necessary to install the proper firmware (or microcode) files and build them into the kernel, as shown below.

These files should be installed in the system before the kernel recompilation using, for example, the command

See amdgpu and iwlwifi wiki pages for more information.

GRUB settings
Edit/update the following line in the following file:

Display backlight
To control the display backlight install. This comes with a system udev rule recommended by the upstream author.

Regular system users are not prohibited to alter files in the  filesystem. The included  rule allows users in the   group to set the display brightness.

Keyboard backlight
The keyboard backlight is working out of the box, and can be controlled by using the + keys without any further adjustments. There are 3 predefined steps of the keyboard backlight. ,  and. To display the current setting of keyboard backlight use the  command line option for.

To show the available adjustment steps use following command, it will show  steps.

To display the current setting use following command:

Unable to write to IOMMU
Sometimes (most of the time) I am getting the following kernel message when booting the system:

Later, in the kernel log, one can find the following line:

It seems that IOMMU works just fine and the first message is a result of a premature initialization of the IOMMU system. According to other reports found on the internet, it can be ignored. Still, it pollutes the screen during a silent boot process.

Slow/unresponsive system after direct reboot from Microsoft Window 10
In kernel versions from 5.4 to 5.6.13 some issues related to MMC/SDHCI driver for Genesys Logic GLI9750 occur after direct reboot from Microsoft Windows 10. The system becomes slow with a few kernel threads using 100% of CPU trying to access MMC/SDHCI device. The issue has been reported (kernel bug [//bugzilla.kernel.org/show_bug.cgi?id=205871 #205871]) and fixed in kernels 5.4.42 and 5.6.14.

AMDGPU always on 100%
Verify frequency GPU currently uses, it should be at 400MHz, but it is stucked permanently at 1200MHz and does not get back to the lowest frequency available. Verify without using hardware specific tools:

Verify the Memory Clock using the hardware specific tool.

Create a file dump:

View dump:

Notice the Memory Clock is always at 100%, making the laptop heat up more than usual and consume the battery faster.

This issue is still being investigated, check the current status of the open bug.

External resources

 * Memory clock always at 100% on the thinkpad T495