LCD backlight

It seems that we have no more issues with LCD and backlight management. LCD switches on/off flawlessly, so does LCD backlight :)

I've just fixed a problem with backlight not enabling after it was disabled. I've discussed PWM-problems with my friend Ordog (it's his nickname), and he suggested to play with PWM frequency; he described how it can work, and proposed some reasons why it doesn't enable in my case. I decided that backlight needs wormup to switch on properly, I've checked this hypothesis - and it works! Backlight switches on properly after short "warmup". So, thanks to Ordog!

Yesterday I've submited my patchset to the linux-arm-kernel maillist. I still have no response about rx1950-related patches, but s3c2440-udc related patch brought up small discussion. You can read it on linux-arm-kernel maillist archive if you're interested in it :)

Comments

Post a Comment

Popular posts from this blog

Access point with Raspberry Pi and rtl8192cu dongle

On Thursday ethernet ports (WAN and LAN1-4) in my Asus WL500GPv1 router have completely died, so I needed a replacement. Hopefully, recently I've got Raspberry Pi, so I decided to use it as a router. I've got TP-LINK TL-WN821NC USB stick from local store which is based on RTL8192CU chipset. Unfortunately, its driver doesn't work with vanilla hostapd, but requires patched ancient version of hostapd from Realtek . I'm using Archlinux on my rpi and I've found manual how to setup AP using this USB stick  here , but I don't want to overwrite binaries from repository packages, since it's not a sane way, and it can (and will) be broken by hostapd update. So I prepared a package, here's source package (just unpack it and build with makepkg directly on rpi), and here's binary package for armv6h (you can install it with pacman -U). I can't put PKGBUILD in AUR, since there's no stable hosting for Realtek's hostapd. If anyone is willing to host
Read more

OLED brightness in Linux

Recently I've got a new laptop with OLED panel only to find out that brightness control for OLED panels is not yet supported in Linux. Archlinux wiki page mentions using gamma ramp for controlling perceived brightness using hackish userspace tools (icc-brightness), so my first thought was to implement a hack for i915 driver to expose backlight interface that actually adjusts gamma ramp. So I went to #dri-devel to ask around whether this idea sounds too crazy and it turned out that there are better ways than using gamma ramp. Basically if you use gamma ramp you essentially reduce dynamic range, i.e. if you have 8 bits per pixel at 50% brightness you would get 7 bit, at 25% - 6 bit and that will result in banding artefacts at low brightness levels. To overcome that issue OLED panels actually have an interface to control brightness. There are at least 2 competing "standards" - VESA and Intel proprietary. First one is already supported by i915 driver while latter is not. Unfo
Read more

Wayland and software rendering

Image
Recently I spent few evenings for hacking wayland . I like idea of wayland - rendering is done completely on client (in whatever way), compositor (server part) is responsible in rendering buffers from clients on the screen. Issue for me was rendering part of weston (reference compositor for wayland) - it uses GLES for compositing, but I want to try wayland and weston on devices without hw acceleration (pure software rendering), and running software GL on PXA270@312MHz does not sound like a good idea, does it? :) So I asked on #wayland@irc.freenode.org if it possible to implement software renderer, Kristian Høgsberg (khr) responded that in master branch of weston repo there's a nice abstraction of renderer, so it's possible to implement pixman renderer. So I did :) weston with x11-backend and pixman renderer khr and pq from #wayland were very helpful, and described place of renderer in wayland architecture, here're some points renderer just performs rendering of
Read more