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AMD

The Radeon DRM/KMS driver in the 3.4 kernel will support Southern Islands (SI) and Trinity (TN) family graphics cores (1, 2, 3, 4 and others). The SI generation, also known as RAxx, includes the Tahiti, Pitcairn and Verde graphics chips found on the mid- to high-end cards which make up the Radeon HD 7700, 7800 and 7900 series. A Gallium3D driver for Mesa 3D which works in conjunction with the kernel's DRM/KMS driver is under development. A pre-release version was released in early April. Once released, a driver for X Server from X.Org (DDX/Device Dependent X) will also make use of this Gallium3D driver for acceleration functions.

Trinity is the code name for a processor series equipped with an on-board graphics core, which AMD is expected to unveil within the next few weeks. They are expected to inherit the Llano processors from AMD's A-series, which is primarily used in lower- to mid-priced desktops and laptops. Merging of support for the Trinity GPU into the kernel was quickly followed by the release of version 6.14.4 of the Radeon driver for X-Org's X Server, which now supports the Trinity graphics core (aka Aruba). The speed with which this occurred was a result of the similarities between this GPU and the Cayman chip. The latter belongs to the Northern Islands chip generation (found on many 6000 series cards) and has been supported for a while now. At the same time, AMD developers have also added Trinity GPU support to libdrm and the Mesa 3D developer tree.

The "Coming in 3.4" series

The Kernel Log can already share an overview of the most important new features of Linux 3.4, expected in the second half of May, since the kernel hackers have integrated all the major changes in the first two development weeks. Hence the 3.4 kernel is currently in its stabilisation phase, in which the kernel developers avoid big changes and focus on fixing bugs.

These articles on the changes and additions discuss the kernel's various functional areas one by one:

This article concludes the "Coming in 3.4" series. Once the final Linux 3.4 kernel is released, a "What's new in Linux 3.4" feature article will be published with an overview of the most important changes in the new version.

Linux 3.4 adds 2D tiling support for Northern Islands chips and the earlier Evergreen chips (found on many 5000 series cards). The technology distributes data differently within the graphics memory, which can result in improved performance. It can be used in conjunction with Radeon's x86-video-ati 6.14.4 DDX driver.

Meanwhile, a two-line change merged into kernel 3.4 means that DisplayPort on VGA adapters on A-series processors (aka Nutmeg) should finally work. The fix was produced following several weeks of bug-hunting, described by developer Jerome Glisse in his blog post, "Weeks in the life of GPU driver developer", which illustrates the lengths to which kernel developers sometimes have to go.

Intel

Intel developers have merged a patch which means that Linux 3.4 will now use RC6, the graphics core power-saving feature, by default on Sandy Bridge processors that contain a GPU (graphics processing unit). As this feature typically reduces power consumption when idling by between three and five watts, this should noticeably extend laptop battery life and tangibly reduce noise levels, since the fan will have less hot air to expel from a system. It can also be activated on earlier Linux kernels by using the kernel parameter i915.i915_enable_rc6=1, though this may lead to crashes or image errors on some systems. Intel is hoping that disabling RC6's deep sleep mode will put an end to these problems. According to the Intel development team, the power savings offered by this mode are marginally better when compared to those offered by the shallower sleep mode. Users who want to use the deep sleep mode on Sandy Bridge GPUs can activate it using kernel parameters implemented by a further patch merged into Linux 3.4.

The Intel development team has also fixed a bug in Intel's i915 DRM/KMS driver which resulted in occasional memory corruption when waking from hibernate/software suspend/ACPI S4; the problem has been around for more than a year. The fix has also been merged into stable and long-term kernels 3.0.27, 3.2.14 and 3.3.1.

From 3.4, the Intel driver will also support interlacing in HDMI and SDVO outputs (1, 2). On more recent graphics cores, the i915 DRM/KMS driver will now utilise the previous unused swizzling and ppgtt features, which can give minor graphics performance boosts. During the course of the stabilisation phase, problems were detected involving the interplay between DMA remapping (required for VT-d) and ppgtt. Consequently, the kernel will use the latter only where DMA remapping is deactivated – where, for example, VT-d is deactivated in the BIOS.

Next: USB displays, hybrid operation

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