[Arm-netbook] MeLe A10 Display Mode Support

[Jaroslaw Niec]

> From: henrik at henriknordstrom.net
> My understanding is that the A10 is capable of
>
> - direct FB playback
> - playback in a movable 2D overlay region of the screen. There is a
> (limited) number of these 2D overlays available.
> - indirect playback via a 3D texture drawn into by the VPU and rendered
> by the GPU.
>
> In neither case you use the GPU for video decoding. At most YUV-RGB
> transformation.
>
Changed topic of this thread to better suit the discussion. No matter how the video is decoded,it must still be presented synchronized tothe display clock driving the HDMI or VGA port.  If you look at the source andsettings available in Android, you will see they only offer a limited set oftimings: Under:https://github.com/amery/linux-allwinner/blob/leak-lichee-3.0.8/drivers/video/sun4i/hdmi/drv_hdmi.c You will see they are missing 23.976 and 59.940.  There are movies for example encoded in both23.976 and 24.000 fps so you must have a way to set both modes individually. The reason I think a custom modeline might solve the problem is that looking into: https://github.com/amery/linux-allwinner/blob/leak-lichee-3.0.8/drivers/video/sun4i/disp/de_bsp/de/disp_clk.c You find a table that corresponds to the pre-defined output modes available in Android.  Hopefully the hardwaresupports timings that are not included in this table so we can manually define a proper 23.976 and 24.000 modefor example.  I have not seen where one can define the other video timing related parameters such as horizontaland vertical sync width, front/back porch, and pixel counts._______________________________________________arm-netbook mailing list arm-netbook at lists.phcomp.co.ukhttp://lists.phcomp.co.uk/mailman/listinfo/arm-netbookSend large attachments to arm-netbook at files.phcomp.co.uk
I have gone through files that Mark posted and found another one that is also important
https://github.com/amery/linux-allwinner/blob/leak-lichee-3.0.8/drivers/video/sun4i/hdmi/aw/hdmi_core.c
I have compared parameters from these files to HDMI Specification and it looks like that the only way to have 23.976 and 59.940 is to reduce HDMI clocks.
For example from 74.25 MHz to 74.176 MHz or from 148.5 MHz to 148.352 MHz. All other HDMI mode parameters (like HBP HFP HPSW VT VBP VFP VPSW) are exactly the same for 24 and  23.976 or for 60 and 59.940.
Unfortunately all these frequencies are derived from one PLL frequency 297MHz. So it looks like that the only way is to reduce this main freq. In my opinion it should be set to 296,704MHz.
This PLL clock is in theory programmable (LCD/TV output uses different freq) by function disp_pll_set from disp_clk.c.
But this is only theory and I don't know what is a resolution of this PLL clock and if we can reduce it to exactly 296.704MHz.
It will be good to have detailed specification of A10 to check this PLL and HDMI registers.
Another question is how the audio will be send when we reduce main clock? Will it slow down? 
Unfortunately I wont have enough time in near future to test all of this. But maybe someone else will try :)
Also maybe someone know if HDMI-CEC line is connected with A10 in Mele? 
I think there is no driver for this right now, but if line is connected with some PIN than it should be possible to write it.
Regards,
Jarek
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