成功安装 Ubuntu (14.04) 后，我遇到了一个奇怪的问题，屏幕上不时出现水平线。我在 Windows7 上检查它，一切正常。之前格式化之前，我也安装过 Ubuntu 14.04，但我没有遇到这个问题。只有一条线出现（在不同的地方）并同时消失。即使在 ubuntu 日志屏幕上也显示线条，它大多发生在启动时，一段时间后它几乎停止了。
视频：https://www.dropbox.com/s/mk9d5dgqtsqgn34/20160121_235234.mp4?dl=0 （抱歉质量较差，但您可以看到 0:32、0:47、1:07、1:33 中的几行）
一些信息：
przem@przem:~$ lspci -nn | grep VGA 01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] RV710/M92 [Mobility Radeon HD 4330/4350/4550][1002:9552]
przem@przem:~$ dmesg | egrep 'drm|radeon'
[ 12.840642] [drm] Initialized drm 1.1.0 20060810
[ 12.986443] [drm] radeon kernel modesetting enabled.
[ 12.986517] fb: switching to radeondrmfb from VESA VGA
[ 12.988823] [drm] initializing kernel modesetting (RV710 0x1002:0x9552 0x144D:0xC050).
[ 12.988839] [drm] register mmio base: 0xCFEF0000
[ 12.988841] [drm] register mmio size: 65536
[ 12.989043] radeon 0000:01:00.0: VRAM: 512M 0x0000000000000000 - 0x000000001FFFFFFF (512M used)
[ 12.989047] radeon 0000:01:00.0: GTT: 1024M 0x0000000020000000 - 0x000000005FFFFFFF
[ 12.989049] [drm] Detected VRAM RAM=512M, BAR=256M
[ 12.989051] [drm] RAM width 64bits DDR
[ 12.989509] [drm] radeon: 512M of VRAM memory ready
[ 12.989511] [drm] radeon: 1024M of GTT memory ready.
[ 12.989528] [drm] Loading RV710 Microcode
[ 13.574567] [drm] radeon: dpm initialized
[ 13.598034] [drm] GART: num cpu pages 262144, num gpu pages 262144
[ 13.611820] [drm] PCIE GART of 1024M enabled (table at 0x000000000025E000).
[ 13.611883] radeon 0000:01:00.0: WB enabled
[ 13.611888] radeon 0000:01:00.0: fence driver on ring 0 use gpu addr 0x0000000020000c00 and cpu addr 0xffd36c00
[ 13.611891] radeon 0000:01:00.0: fence driver on ring 3 use gpu addr 0x0000000020000c0c and cpu addr 0xffd36c0c
[ 13.612891] radeon 0000:01:00.0: fence driver on ring 5 use gpu addr 0x000000000005c598 and cpu addr 0xf8e9c598
[ 13.612895] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 13.612897] [drm] Driver supports precise vblank timestamp query.
[ 13.612899] radeon 0000:01:00.0: radeon: MSI limited to 32-bit
[ 13.612947] radeon 0000:01:00.0: radeon: using MSI.
[ 13.612981] [drm] radeon: irq initialized.
[ 13.659269] [drm] ring test on 0 succeeded in 1 usecs
[ 13.659278] [drm] ring test on 3 succeeded in 4 usecs
[ 13.834216] [drm] ring test on 5 succeeded in 1 usecs
[ 13.834225] [drm] UVD initialized successfully.
[ 13.834439] [drm] ib test on ring 0 succeeded in 0 usecs
[ 13.834463] [drm] ib test on ring 3 succeeded in 0 usecs
[ 14.480110] [drm] ib test on ring 5 succeeded
[ 14.481403] [drm] radeon atom DIG backlight initialized
[ 14.481406] [drm] Radeon Display Connectors
[ 14.481408] [drm] Connector 0:
[ 14.481410] [drm] LVDS-1
[ 14.481412] [drm] DDC: 0x7e50 0x7e50 0x7e54 0x7e54 0x7e58 0x7e58 0x7e5c 0x7e5c
[ 14.481414] [drm] Encoders:
[ 14.481415] [drm] LCD1: INTERNAL_UNIPHY2
[ 14.481417] [drm] Connector 1:
[ 14.481418] [drm] VGA-1
[ 14.481420] [drm] DDC: 0x7e40 0x7e40 0x7e44 0x7e44 0x7e48 0x7e48 0x7e4c 0x7e4c
[ 14.481422] [drm] Encoders:
[ 14.481423] [drm] CRT1: INTERNAL_KLDSCP_DAC1
[ 14.481425] [drm] Connector 2:
[ 14.481426] [drm] HDMI-A-1
[ 14.481428] [drm] HPD1
[ 14.481430] [drm] DDC: 0x7fa0 0x7fa0 0x7fa4 0x7fa4 0x7fa8 0x7fa8 0x7fac 0x7fac
[ 14.481431] [drm] Encoders:
[ 14.481433] [drm] DFP1: INTERNAL_UNIPHY
[ 15.459388] [drm] fb mappable at 0xD045F000
[ 15.459392] [drm] vram apper at 0xD0000000
[ 15.459394] [drm] size 4325376
[ 15.459396] [drm] fb depth is 24
[ 15.459397] [drm] pitch is 5632
[ 15.459512] fbcon: radeondrmfb (fb0) is primary device
[ 15.459632] radeon 0000:01:00.0: fb0: radeondrmfb frame buffer device
[ 15.459634] radeon 0000:01:00.0: registered panic notifier
[ 15.478772] [drm] Initialized radeon 2.40.0 20080528 for 0000:01:00.0 on minor 0
请帮我找到解决方案。