I hope you find this adventure interesting, and I hope you
provide me with some insight.
Recently, I booted my computer, a Dell Latitude D810 that has a
Radeon Mobility x600 (R300); all systems were waking up as normal:
* The Dell logo popped up in some ancient VGA mode.
* The GRUB menu appeared for 3 seconds as instructed.
* Linux loaded and started spewing out log messages.
and then:
BAM!
At around:
2011-09-09 20:27:07 +0000
the Darkness overcame me; my laptop's LCD panel went black with nary
a sign of life. After poking around a bit via ssh, I couldn't figure
out what was going on; I had been running all the relevant code
without trouble for some time now, so it just didn't make sense, and
I began suspecting hardware failure.
I strolled on over to freenode/#radeon, where I explained that I was
still getting graphics at early boot time, but that it was dying
shortly after Linux loaded. A one named Tari suggested that I boot
with `nomodeset' in order to avoid anything more complicated than
the standards of the Ancients.
And Lo! With that very kernel command line parameter, the boot
process did indeed land me safely in a working, albeit cramped
VGA-backed virtual console.
Searching the logs a bit more revealed the following:
[drm:drm_calc_timestamping_constants] *ERROR* crtc 10: Can't
calculate constants, dotclock = 0!
Then (skipping a few interesting adventures), I ultimately discovered
this kernel message:
[drm] Panel Size 1920x4095
which is curious indeed!, because my laptop's panel size should be
`1920x1200'. I booted into the computer's BIOS only to find that
it too was being fooled into thinking that the display dimensions
are `1920x4095'.
Why might this have happened? Are bits stuck? Did something get fried?
Naturally, I set off to hardcode the right values into the DRM/KMS
Radeon driver, and after overturning stones, scraping away ivy,
digging tunnels, and wading through forgotten moats, I managed to
make my way to the beginning of that labyrinthine beast, where I
could successfully exert my will:
diff --git a/drivers/gpu/drm/radeon/radeon_combios.c b/drivers/gpu/drm/radeon/radeon_combios.c
index 6367524..9119dd6 100644
--- a/drivers/gpu/drm/radeon/radeon_combios.c
+++ b/drivers/gpu/drm/radeon/radeon_combios.c
@@ -1245,7 +1245,7 @@ struct radeon_encoder_lvds *radeon_combios_get_lvds_info(struct radeon_encoder
DRM_INFO("Panel ID String: %s\n", stmp);
lvds->native_mode.hdisplay = RBIOS16(lcd_info + 0x19);
- lvds->native_mode.vdisplay = RBIOS16(lcd_info + 0x1b);
+ lvds->native_mode.vdisplay = 1200; /*RBIOS16(lcd_info + 0x1b);*/
DRM_INFO("Panel Size %dx%d\n", lvds->native_mode.hdisplay,
lvds->native_mode.vdisplay);
With that small change, the driver in question loaded none the wiser,
yielding a KMS-driven frame-buffer-backed virtual console as desired:
[drm] radeon defaulting to kernel modesetting.
[drm] radeon kernel modesetting enabled.
...
[drm] Panel Size 1920x1200
...
[drm] fb depth is 24
[drm] pitch is 7680
fbcon: radeondrmfb (fb0) is primary device
Console: switching to colour frame buffer device 240x75
fb0: radeondrmfb frame buffer device
Unfortunately, X marks the spot where things get hairy again.
Most noticeably, when I run:
startx
I get an Xorg.log that looks unblemished, yet X clearly renders the
screen based on an erroneous DPI. In fact, even though Xorg.log
clearly shows:
(**) RADEON(0): Display dimensions: (331, 207) mm
(**) RADEON(0): DPI set to (147, 147)
I end up getting the following from xdpyinfo:
dimensions: 1920x1200 pixels (507x317 millimeters)
resolution: 96x96 dots per inch
Why is this the case?
Fortunately, I can solve the DPI issue by specifying the desired
value directly on the command line:
startx -- -dpi 147
Why does this work when xorg.conf does not? (especially given that
xorg.conf alone used to be enough to achieve the desired effect).
Unfortunately, the troubles do not end there. Rudimentary benchmarking
(playing 720p H.264 videos, running glxgears, etc.) indicates by low
CPU usage that hardware acceleration is indeed enabled, which is in
agreement with all the logs and diagnostics:
Linux:
[drm] radeon: 128M of VRAM memory ready
[drm] radeon: 512M of GTT memory ready.
...
[drm] radeon: 1 quad pipes, 1 Z pipes initialized.
[drm] PCIE GART of 512M enabled (table at 0xD0040000).
Xorg:
(II) [KMS] Kernel modesetting enabled.
...
(==) RADEON(0): Depth 24, (--) framebuffer bpp 32
(II) RADEON(0): Pixel depth = 24 bits stored in 4 bytes (32 bpp pixmaps)
(==) RADEON(0): Default visual is TrueColor
(==) RADEON(0): RGB weight 888
(II) RADEON(0): Using 8 bits per RGB (8 bit DAC)
(--) RADEON(0): Chipset: "ATI Radeon Mobility X600 (M24) 3150 (PCIE)" (ChipID = 0x3150)
...
(II) RADEON(0): KMS Color Tiling: enabled
(II) RADEON(0): KMS Pageflipping: enabled
(II) RADEON(0): SwapBuffers wait for vsync: enabled
...
(++) RADEON(0): DPI set to (147, 147)
...
(II) RADEON(0): [DRI2] Setup complete
(II) RADEON(0): [DRI2] DRI driver: r300
...
(II) RADEON(0): Direct rendering enabled
(II) RADEON(0): Render acceleration enabled for R300/R400/R500 type cards.
...
(II) EXA(0): Driver allocated offscreen pixmaps
(II) EXA(0): Driver registered support for the following operations:
(II) Solid
(II) Copy
(II) Composite (RENDER acceleration)
(II) UploadToScreen
(II) DownloadFromScreen
(II) RADEON(0): Acceleration enabled
(==) RADEON(0): DPMS enabled
(==) RADEON(0): Silken mouse enabled
(II) RADEON(0): Set up textured video
(II) RADEON(0): RandR 1.2 enabled, ignore the following RandR disabled message.
(--) RandR disabled
...
(II) AIGLX: enabled GLX_MESA_copy_sub_buffer
(II) AIGLX: enabled GLX_INTEL_swap_event
(II) AIGLX: enabled GLX_SGI_swap_control and GLX_MESA_swap_control
(II) AIGLX: enabled GLX_SGI_make_current_read
(II) AIGLX: GLX_EXT_texture_from_pixmap backed by buffer objects
(II) AIGLX: Loaded and initialized /usr/lib/xorg/modules/dri/r300_dri.so
(II) GLX: Initialized DRI2 GL provider for screen 0
(II) RADEON(0): Setting screen physical size to 331 x 207
glxinfo:
direct rendering: Yes
However, within at least some colors, window locations, and so on,
there is this strange but subtle flickering and subtle striation.
The mouse kind of jitters about rather than moving smoothly; the
frame rate seems too low, a fact that is confirmed by glxgears:
$ glxgears
Running synchronized to the vertical refresh. The framerate should
be approximately the same as the monitor refresh rate.
99 frames in 5.0 seconds = 19.628 FPS
97 frames in 5.0 seconds = 19.285 FPS
97 frames in 5.0 seconds = 19.285 FPS
97 frames in 5.0 seconds = 19.285 FPS
97 frames in 5.0 seconds = 19.285 FPS
97 frames in 5.0 seconds = 19.285 FPS
Note that while running glxgears, the CPU is hardly used at all, so
the GPU is pulling its weight. (In contrast, when hardware acceleration
is disabled, the CPU gets pegged at 100%, but more importantly, the FPS
is no longer synchronized to the vertical refresh rate, so it actually
becomes higher (at around 26 FPS), though there are still the same
problems of flickering and striation).
Thus, the vertical refresh rate is in fact the bottleneck. Consider
these:
Xorg:
(II) RADEON(0): Printing probed modes for output LVDS
(II) RADEON(0): Modeline "1920x1200"x9.4 162.00 1920 2016 2072 2160 1200 49753 49756 7985 (75.0 kHz)
...
(II) RADEON(0): Output LVDS using initial mode 1920x1200
xrandr --verbose:
1920x1200 (0x55) 162.0MHz *current +preferred
h: width 1920 start 2016 end 2072 total 2160 skew 0 clock 75.0KHz
v: height 1200 start 49753 end 49756 total 7985 clock 9.4Hz
That's right: A vertical refresh of 9.4Hz! You can see from the
vertical `start', `end', and `total' numbers in the xrandr output
that something really bizarre is going on (there are other wrong
data besides just the panel height).
Is the striation from some kind of interlacing? (after all, 9.4*2 Hz
is ALMOST near the FPS reported by glxgears).
What other bits can I hardcode in the software? What might be failing?
Interestingly, Xorg.conf and xrandr report other, seemingly correct
modelines (which I assume are supplied by built-in alternatives):
Xorg:
(II) RADEON(0): Printing probed modes for output LVDS
(II) RADEON(0): Modeline "1920x1200"x9.4 162.00 1920 2016 2072 2160 1200 49753 49756 7985 (75.0 kHz)
(II) RADEON(0): Modeline "1920x1080"x60.0 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync (67.2 kHz)
(II) RADEON(0): Modeline "1600x1200"x59.9 161.00 1600 1712 1880 2160 1200 1203 1207 1245 -hsync +vsync (74.5 kHz)
(II) RADEON(0): Modeline "1680x1050"x60.0 146.25 1680 1784 1960 2240 1050 1053 1059 1089 -hsync +vsync (65.3 kHz)
(II) RADEON(0): Modeline "1400x1050"x60.0 121.75 1400 1488 1632 1864 1050 1053 1057 1089 -hsync +vsync (65.3 kHz)
(II) RADEON(0): Modeline "1280x1024"x59.9 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync (63.7 kHz)
(II) RADEON(0): Modeline "1440x900"x59.9 106.50 1440 1528 1672 1904 900 903 909 934 -hsync +vsync (55.9 kHz)
(II) RADEON(0): Modeline "1280x960"x59.9 101.25 1280 1360 1488 1696 960 963 967 996 -hsync +vsync (59.7 kHz)
(II) RADEON(0): Modeline "1280x854"x59.9 89.25 1280 1352 1480 1680 854 857 867 887 -hsync +vsync (53.1 kHz)
(II) RADEON(0): Modeline "1280x800"x59.8 83.50 1280 1352 1480 1680 800 803 809 831 -hsync +vsync (49.7 kHz)
(II) RADEON(0): Modeline "1280x720"x59.9 74.50 1280 1344 1472 1664 720 723 728 748 -hsync +vsync (44.8 kHz)
(II) RADEON(0): Modeline "1152x768"x59.8 71.75 1152 1216 1328 1504 768 771 781 798 -hsync +vsync (47.7 kHz)
(II) RADEON(0): Modeline "1024x768"x59.9 63.50 1024 1072 1176 1328 768 771 775 798 -hsync +vsync (47.8 kHz)
(II) RADEON(0): Modeline "800x600"x59.9 38.25 800 832 912 1024 600 603 607 624 -hsync +vsync (37.4 kHz)
(II) RADEON(0): Modeline "848x480"x59.7 31.50 848 872 952 1056 480 483 493 500 -hsync +vsync (29.8 kHz)
(II) RADEON(0): Modeline "720x480"x59.7 26.75 720 744 808 896 480 483 493 500 -hsync +vsync (29.9 kHz)
(II) RADEON(0): Modeline "640x480"x59.4 23.75 640 664 720 800 480 483 487 500 -hsync +vsync (29.7 kHz)
...
(II) RADEON(0): Output LVDS using initial mode 1920x1200
xrandr:
1920x1200 (0x55) 162.0MHz +preferred
h: width 1920 start 2016 end 2072 total 2160 skew 0 clock 75.0KHz
v: height 1200 start 49753 end 49756 total 7985 clock 9.4Hz
1920x1080 (0x56) 173.0MHz -HSync +VSync
h: width 1920 start 2048 end 2248 total 2576 skew 0 clock 67.2KHz
v: height 1080 start 1083 end 1088 total 1120 clock 60.0Hz
1600x1200 (0x57) 161.0MHz -HSync +VSync
h: width 1600 start 1712 end 1880 total 2160 skew 0 clock 74.5KHz
v: height 1200 start 1203 end 1207 total 1245 clock 59.9Hz
1680x1050 (0x58) 146.2MHz -HSync +VSync
h: width 1680 start 1784 end 1960 total 2240 skew 0 clock 65.3KHz
v: height 1050 start 1053 end 1059 total 1089 clock 60.0Hz
1400x1050 (0x59) 121.8MHz -HSync +VSync
h: width 1400 start 1488 end 1632 total 1864 skew 0 clock 65.3KHz
v: height 1050 start 1053 end 1057 total 1089 clock 60.0Hz
1280x1024 (0x5a) 109.0MHz -HSync +VSync
h: width 1280 start 1368 end 1496 total 1712 skew 0 clock 63.7KHz
v: height 1024 start 1027 end 1034 total 1063 clock 59.9Hz
1440x900 (0x5b) 106.5MHz -HSync +VSync
h: width 1440 start 1528 end 1672 total 1904 skew 0 clock 55.9KHz
v: height 900 start 903 end 909 total 934 clock 59.9Hz
1280x960 (0x5c) 101.2MHz -HSync +VSync
h: width 1280 start 1360 end 1488 total 1696 skew 0 clock 59.7KHz
v: height 960 start 963 end 967 total 996 clock 59.9Hz
1280x854 (0x5d) 89.2MHz -HSync +VSync
h: width 1280 start 1352 end 1480 total 1680 skew 0 clock 53.1KHz
v: height 854 start 857 end 867 total 887 clock 59.9Hz
1280x800 (0x5e) 83.5MHz -HSync +VSync
h: width 1280 start 1352 end 1480 total 1680 skew 0 clock 49.7KHz
v: height 800 start 803 end 809 total 831 clock 59.8Hz
1280x720 (0x5f) 74.5MHz -HSync +VSync
h: width 1280 start 1344 end 1472 total 1664 skew 0 clock 44.8KHz
v: height 720 start 723 end 728 total 748 clock 59.9Hz
1152x768 (0x60) 71.8MHz -HSync +VSync
h: width 1152 start 1216 end 1328 total 1504 skew 0 clock 47.7KHz
v: height 768 start 771 end 781 total 798 clock 59.8Hz
1024x768 (0x61) 63.5MHz -HSync +VSync
h: width 1024 start 1072 end 1176 total 1328 skew 0 clock 47.8KHz
v: height 768 start 771 end 775 total 798 clock 59.9Hz
800x600 (0x62) 38.2MHz -HSync +VSync
h: width 800 start 832 end 912 total 1024 skew 0 clock 37.4KHz
v: height 600 start 603 end 607 total 624 clock 59.9Hz
848x480 (0x63) 31.5MHz -HSync +VSync
h: width 848 start 872 end 952 total 1056 skew 0 clock 29.8KHz
v: height 480 start 483 end 493 total 500 clock 59.7Hz
720x480 (0x64) 26.8MHz -HSync +VSync
h: width 720 start 744 end 808 total 896 skew 0 clock 29.9KHz
v: height 480 start 483 end 493 total 500 clock 59.7Hz
640x480 (0x65) 23.8MHz -HSync +VSync
h: width 640 start 664 end 720 total 800 skew 0 clock 29.7KHz
v: height 480 start 483 end 487 total 500 clock 59.4Hz
However, switching to one of these other modes or defining my own
through xorg.conf does nothing to fix the troubles; while the
resolution does change, the flickering and striation remain, and
glxgears continues to report the same 19+ FPS.
Is there anything that can be done to work around these last
troubles?
Sincerely,
Michael Witten
P.S.
I'm running i686 Linux 3.1.0-rc5, specifically this commit
(with my patch):
473e2bc9d3649e072d0a1bff84afa95b072d056b
and:
X.Org X Server 1.10.3.901 (1.10.4 RC 1)
Release Date: 2011-07-29
X Protocol Version 11, Revision 0
Kernel command line: root=/dev/sda2 ro 3
Build Date: 08 August 2011 08:28:07AM
Current version of pixman: 0.22.2
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