[Intel-gfx] [PATCH 0/3] fbdev no more!

[David Herrmann]

Hi

On Sun, Jun 16, 2013 at 4:57 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> Hi all,
>
> So I've taken a look again at the locking mess in our fbdev support and cried.
> Fixing up the console_lock mess around the fbdev notifier will be real work,
> semanatically the fbdev layer does lots of stupid things (like the radeon resume
> issue I've just debugged) and the panic notifier is pretty much a lost cause.

Hint: Take a look at fbdev ref-counting or sysfs integration. Totally
broken, too. I sometimes really wonder how that still works.

> So I've decided to instead rip it all out. It seems to work \o/

Yep, works for me pretty well, too.

> Of course a general purpose distro propably wants David's kmscon for any
> fallbacks needs and a system compositor to ditch the VT subsystem - atm my
> machine here runs with the dummy console so that VT switching between different
> X sessions still works ;-)

I used CONFIG_VT=n for quite a while with user-space VTs as
replacement. But what we really need is a system-compositor (even if
it's not really a "compositor"). But for that we need dynamic modeset
nodes or we end up with the same problems as with VTs. It's on my TODO
list after render/modeset nodes are done. With user-space VTs this is
even backwards-compatible.

> Oh and: At least fedora's boot splash seems to be unhappy about the lack of an
> fbdev (it doesn't seem to do anything), which breaks early disk encryption a
> bit. The black screen itself shouldn't be a big issue at least for i915, since
> with all the fastboot work we can just hang onto the current config and
> framebuffer (one missing patch from Chris for the fb preservartion). So as long
> as the bios/grub put up something nice, it'll look ok.

Plymouth should work just fine with KMS (afaik it was even airlied who
wrote the backends). It doesn't support GPU hotplugging, though. So
it's probably started before i915 is loaded and so doesn't pick up the
DRM device. Or with initrd user-space is started early without waiting
for device-initialization to finish. So even with i915 built-in it may
run before card0 shows up. The journal-log should probably help
debugging this.

Btw., It has /dev/dri/card0 hard-coded and only tries opening it once
during startup.

> So just a small step here really, but imo into the right direction. Now, please
> bring on the flames!

Please, apply it! Now!

Thanks
David

> Aside: We can hide the #ifdef mess a bit better in drm/i915 I think, but I'd
> like to wait for a bit of feedback first. And one more: This also removes the
> console_lock completely from our critical path in suspend/resume!
>
> One thing I haven't wasted a single thought about is kgdb and panic notifier
> support. But since the current code is pretty decently broken already (we have
> _tons_ of mutex grabbing and waits in there) I don't think people care that much
> about it anyway. Using a sprite to smash the kgdb/panic output on top of
> whatever's currently displaying might be an approach.
>
> Cheers, Daniel
>
> Daniel Vetter (3):
>   drm: Add separate Kconfig option for fbdev helpers
>   drm/i915: Kconfig option to disable the legacy fbdev support
>   drm/i915: rename intel_fb.c to intel_fbdev.c
>
>  drivers/gpu/drm/Kconfig              |  57 ++-----
>  drivers/gpu/drm/Makefile             |   3 +-
>  drivers/gpu/drm/ast/Kconfig          |   1 +
>  drivers/gpu/drm/cirrus/Kconfig       |   1 +
>  drivers/gpu/drm/exynos/Kconfig       |   1 +
>  drivers/gpu/drm/gma500/Kconfig       |   1 +
>  drivers/gpu/drm/i915/Kconfig         |  56 +++++++
>  drivers/gpu/drm/i915/Makefile        |   3 +-
>  drivers/gpu/drm/i915/i915_debugfs.c  |   4 +-
>  drivers/gpu/drm/i915/i915_dma.c      |   8 +-
>  drivers/gpu/drm/i915/i915_drv.h      |   2 +
>  drivers/gpu/drm/i915/intel_display.c |  12 +-
>  drivers/gpu/drm/i915/intel_drv.h     |  39 ++++-
>  drivers/gpu/drm/i915/intel_fb.c      | 314 -----------------------------------
>  drivers/gpu/drm/i915/intel_fbdev.c   | 314 +++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/mgag200/Kconfig      |   1 +
>  drivers/gpu/drm/nouveau/Kconfig      |   1 +
>  drivers/gpu/drm/omapdrm/Kconfig      |   1 +
>  drivers/gpu/drm/qxl/Kconfig          |   1 +
>  drivers/gpu/drm/shmobile/Kconfig     |   1 +
>  drivers/gpu/drm/tilcdc/Kconfig       |   1 +
>  drivers/gpu/drm/udl/Kconfig          |   1 +
>  drivers/gpu/host1x/drm/Kconfig       |   1 +
>  drivers/staging/imx-drm/Kconfig      |   1 +
>  24 files changed, 452 insertions(+), 373 deletions(-)
>  create mode 100644 drivers/gpu/drm/i915/Kconfig
>  delete mode 100644 drivers/gpu/drm/i915/intel_fb.c
>  create mode 100644 drivers/gpu/drm/i915/intel_fbdev.c
>
> --
> 1.7.11.7
>
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