Atomic mode-setting drivers

[Daniel Vetter]

On Fri, Mar 04, 2016 at 06:08:16PM +0000, Emil Velikov wrote:
> On 4 March 2016 at 16:32, Daniel Vetter <daniel at ffwll.ch> wrote:
> > Adding relevant mailing lists and people. Please don't send private
> > mails to maintainers ;-)
> >
> > On Fri, Mar 4, 2016 at 1:47 PM, Chih-Wei Huang <cwhuang at android-x86.org> wrote:
> >> Hi Daniel,
> >> This is the Android-x86 project.
> >> I'm looking for info about atomic mode-setting drivers
> >> and then found your presentation at
> >> http://www.x.org/wiki/Events/XDC2015/Program/xdc-2015.pdf
> >>
> >> Especially page 16 talks about the Android support,
> >> exactly what I want.
> >>
> >> It said "no one has an open-source atomic hwc".
> >> Actually there is one in the AOSP 6.0 release:
> >>
> >> https://android.googlesource.com/platform/external/drm_hwcomposer
> >>
> >> It's developed by the Chromium team.
> >> An update repo is here:
> >> https://chromium.googlesource.com/chromiumos/drm_hwcomposer
> >
> > Yup, my presentation is already outdated - the latest one for LCA2016
> > mentions that hwc exists.
> >
> >> Contributing instructions are here:
> >> https://sites.google.com/a/chromium.org/dev/contributing-to-drm_hwcomposer
> >>
> >> We are trying to enable the drm_hwcomposer for Android-x86.
> >> However, it requires atomic mode-setting drivers
> >> which seems are not ready in the vanilla kernel 4.4,
> >> the kernel we are using now.
> >>
> >> Unfortunately none of us is an expert of kernel drm drivres.
> >> Could you give me a brief status of the
> >> current atomic mode-setting drivers in vanilla kernel?
> >> What are still missing? fences? deadlock?
> >> More important, how much effort do we need
> >> to make them work with AOSP's drm_hwcomposer?
> >
> > There's a pile of drivers, but for classic x86 desktop only i915.ko,
> > and that is still not yet enabled by default. i915.nuclear_pageflip=1
> > will give you experimental atomic support but not sure whether that's
> > good enough for hwcomposer.
> >
> > Fences are being worked on in upstream kernel, but nothing to show
> > yet.. Otherwise I don't know what's all needed to make it, I haven't
> > had a chance to play around with it yet.
> >
> Let's not forget the new AMDGPU code that, according to the summary
> [1], adds ATOMIC support for newer AMD hardware.
> 
> Chih-Wei, there might be an updated branch somewhere you can grab,
> sadly I did not find any. Thus you might have to pick the patches off
> the mailing list, unless we have a patchwork instance for it somewhere
> ?

amdgpu DAL rewrite isn't really atomic unfortunately. I can't tell you how
un-atomic it is since it's such a maze, but there's not much chance it is
useful as an atomic driver.
-Daniel

> 
> >>
> >> More discussion about it can be found in
> >> our devel group:
> >> https://groups.google.com/d/msg/android-x86-devel/RErWaXk3b7g/g_OSPGf4AwAJ
> >
> > Please include that mailing list too, to make sure everyone is on board.
> >
> Not sure why, yet that mailing list is closed for public eyes. Last
> time I checked one has to be invited to read or write to it :-(
> Props to Chih-Wei I'm on it, although others are sure to get the short
> end of the stick.
> 
> Regards,
> Emil
> 
> [1] https://lists.freedesktop.org/archives/dri-devel/2016-February/100524.html

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch