TFT Panel trouble with Raspi

[Bernd Walter]

I'm using the folloging Image:
http://www.peach.ne.jp/archives/rpi/freebsd-pi-clang-20130210.img.gz
With this Panel:
http://www.chalk-elec.com/?page_id=1280#!/~/product/category=3094861&id=14647630

Resolution is 1024x600 pixel with an HDMI adapter.

Under Linux at first it didn't display anything at all.
The following config.txt was required:
hdmi_ignore_edid=0xa5000080
hdmi_group=2
hdmi_mode=16
overscan_top=-40
overscan_bottom=125

This sets 1024x768 and tunes overscan area.
Nice HDMI crap only knows defined resolutions...
Without overscan values the display starts at the right top postion, but
the 168 excessive bottom lines are missing on display - no surprise.
Descriptions claims those to be pixels, so those values don't make 100%
sense to me as math says the result to be 683 pixel, but basicly the
result looks good.
Considering the description it doesn't make sense to tamper with top
values as it is correctly aligned without overscan.

With FreeBSD however those values won't work.
The result is that at top there is empty space and missing lines at
the bottom.
If I set 800x600 resolution everything looks good, but width isn't used
completely.
With description I would assume that setting bottom to 168 should give
the right result, but setting bottom to 168 cuts 84 lines at
bottom and 84 lines at top.
With bottom to 336 the bottom is alligned correctly but missing 168
lines on top.
With bottom to 336 and top to -168 the result is the same as with
bottom at 168 and top at 0.

Under Linux the result is different.
Setting bottom to 168 cuts many more pixel at bottom and less pixel
at top - sigh, so much about their documentation.
I would guess it cuts about 3x at bottom and 1x at top.
Adding top=-10 seems to add symetrical pixel at top and bottom.
Strange enough - booting Linux with the above vendor supplied config
shows this:
[    0.000000] Kernel command line: dma.dmachans=0x7f35 bcm2708_fb.fbwidth=1024 bcm2708_fb.fbheight=683 bcm2708.boardrev=0x3 bcm2708.serial=0xda48bc18 smsc95xx.macaddr=B8:27:EB:48:BC:18 sdhci-bcm2708.emmc_clock_freq=100000000 vc_mem.mem_base=0xec00000 vc_mem.mem_size=0x10000000  dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
fbheigh = 683, but I would say that I would have noticed 83 missing
pixels, although it agrees with my math about those values to be pixels.

Btw - on my LG TV with 1366x768 pixel (it announces as 1360x768 and
scales to 1366 sigh) FreeBSD was missing bottom lines as well.
I know because I plugged it into my TV to boot the FreeBSD for the first
time, didn't get a login and thought there was only a getty running on
serial console.
I didn't debug there any further.
Today with the TFT-Panel I saw that it is indeed running a getty.
Whatever bad magic there is - Linux knows it and FreeBSD has problems.

-- 
B.Walter <bernd at bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.