Weston on framebuffer?

Carsten Haitzler (The Rasterman) raster at rasterman.com
Tue Jul 19 23:04:48 UTC 2016

On Tue, 19 Jul 2016 18:10:16 +0200 Christer Weinigel <christer at weinigel.se>

> Hi,
> I'm trying to port Linux to a Samsung S3C2416 based system (actually an
> oscilloscope, http://blog.weinigel.se/2016/05/01/sds7102-hacking.html).
> The S3C2416 is a 400MHz ARM9 with a fairly dumb framebuffer, it has some
> 2D acceleration (pixel/line drawing with alpha, copy rectangle with
> alpha and/or color key) but as far as I can tell nobody has added Linux
> support for it.
> I'm going to need some kind of GUI for the box and somebody mentioned
> that Weston has framebuffer support nowdays.  I turned on the Weston
> config option in buildroot (2015.5) and managed to get something that
> didn't work to begin with, the OS abstraction stuff requires support for
> posix_fadvise but for some reason that didn't work with ulibc but I
> hacked around that.  libinput didn't like eudev and didn't want to
> recognize a USB keyboard and USB mouse to begin with but I just
> hardcoded the device type instead of relying on udev to tag the devices.
> With this I managed to get a desktop and was unable to start
> wayland-terminal.  Redrawing of the graphics felt fairly snappy, but the
> lag from pressing a key on the keyboard until a character showed up in
> the terminal was slow, probably between a quarter to half a second.
> So my question is if this is the performance I should expect with weston
> on a 400MHz ARM9 and a dumb framebuffer?  Have I done something stupid
> and there are easy ways to speed it up?
> Is there any documentation on how to convert the framebuffer driver for
> the S3C2416 to a KMS driver and how to add acceleration support?  Can
> weston use this?
> Or is wayland/weston not really suited for this kind of old hardware and
> what should I use in that case?
>   /Christer

when you say redraw is snappy... that implies that output is fast. so time from
deciding to render and update and it appearing is very short. but you seem to
have serious input lag which implies to me that it has nothing to do with your
cpu speed and is something else deeper and more involved. time to trace things
and see how they go.

------------- Codito, ergo sum - "I code, therefore I am" --------------
The Rasterman (Carsten Haitzler)    raster at rasterman.com

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