TFT Panel trouble with Raspi

[Bernd Walter]

On Thu, Feb 21, 2013 at 05:10:12AM +0100, Bernd Walter wrote:
> 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.

This point was wrong.
Everthing looks Ok on the LG TV.
But setting overscan_bottom also reduces same amount of pixel on top as
on bottom and not just at the bottom as expected.

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