from the coding-skills-on-display dept.
LinuxGizmos has an interesting article on how an Intel Engineer fixed up Linux's DisplayPort compliance, and got the kernel patch moved upstream.
At ELC 2017, Intel's Manasi Navare described how she patched Linux 4.12 for true DisplayPort compliance, and offered tips on pushing patches upstream.
If you've ever hooked up a Linux computer to a DisplayPort monitor and encountered only a flickering or blank screen, we've got good news for you. A graphics kernel developer at Intel's Open Source Technology Center has solved the problem with a patch that will go into Linux Kernel 4.12. Manasi Navare's patch modifies Atomic Kernel Mode Setting (KMS) technology to gracefully drop down to a lower resolution to display the image.
"Someone had to fix this problem, so I said okay, I have the knowledge and I have the community to help me," said Navare at the recent Embedded Linux Conference.
While display interface standards are slow to move, at the same time their movement is inexorable: monitor resolutions continue to increase, as do refresh rates and color depths, requiring more and more bandwidth to carry signals for the next generation of monitors. Keeping pace with the demand for bandwidth, the DisplayPort standard, the cornerstone of PC display standards, has now been through several revisions since it was first launched over a decade ago. And now this morning the standard is taking its biggest leap yet with the release of the DisplayPort 2.0 specification. Set to offer nearly triple the available bandwidth of DisplayPort 1.4, the new revision of DisplayPort is almost moving a number of previously optional features into the core standard, creating what's in many ways a new baseline for the interface.
The big news here, of course, is raw bandwidth. The current versions of DisplayPort – 1.3 & 1.4 – offer up to 32.4 Gbps of bandwidth – or 25.9 Gbps after overhead – which is enough for a standard 16.7 million color (24-bit) monitor at up to 120Hz, or up to 98Hz for 1 billion+ (30-bit) monitors. This is a lot of bandwidth, but it still isn't enough for the coming generation of monitors, including the likes of Apple's new 6K Pro Display XDR monitor, and of course, 8K monitors. As a result, the need for more display interface bandwidth continues to grow, with these next-generation monitors set to be the tipping point. And all of this is something that the rival HDMI Forum has already prepared for with their own HDMI 2.1 standard.
DisplayPort 2.0, in turn, is shooting for 8K and above. Introducing not just one but a few different bitrate modes, the fastest mode in DisplayPort 2.0 will top out at 80 Gbps of raw bandwidth, about 2.5 times that of DisplayPort 1.3/1.4. Layered on that, DisplayPort 2.0 also introduces a more efficient coding scheme, resulting in much less coding overhead. As a result, the effective bandwidth of the new standard will peak at 77.4 Gbps, with at 2.98x the bandwidth of the previous standard is just a hair under a full trebling of available bandwidth.