Hi, > OK, here's one preliminary theory after I dragged Jason to a conversation > from his weekend in a vacation.
Thanks! Could have waited until Monday of course, but it's great to have another starting point to work on over the weekend. > There could be mis-use of the framebuffer's FBIOPUT_VSCREENINFO as a > way to update the screen instead of using FBIOPAN_DISPLAY. That's exactly what Android does in a couple of places, e.g. system/core/init/logo.c, function fb_update() [that one actually calls FBIOPUT_VSCREENINFO _twice_ to update the screen] hardware/libhardware/modules/gralloc/framebuffer.cpp, function fb_post This should be fairly easy to fix, but googling it, I found an explanation from an upstream engineer on why they're doing it that way -- apparently on some graphics drivers, FBIOPAN_DISPLAY does smooth panning, which obviously isn't what you want for a simple screen refresh. I'm definitely going to change it to see whether or not this is the problem (and also to probably get a bit of a performance boost on Panda) - but I wonder what hardware we're going to break with that. Given other pieces of code (e.g. SDL) use FBIOPAN_DISPLAY for screen refreshes, I think using that ioctl should be mostly safe. > The former > ioctl could take significant amount of time re-calculating the timing > assuming resolution/color depth changes, and re-initializing the controller > for a new mode, and that could result in screen blinking. That is consistent with the messages I'm seeing in dmesg output. Maybe (in addition to fixing userland) the driver should be a bit smarter and not reinitialize the controller if it realizes the old and new modes are actually the same, given Android is probably not the only piece of code that uses FBIOPUT_VSCREENINFO, given apparently some fb drivers interpret FBIOPAN_DISPLAY as something different... ttyl bero _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
