[Letux-kernel] fb tiler considered harmful

H. Nikolaus Schaller hns at goldelico.com
Tue Feb 14 21:56:47 CET 2017


Hi Andreas,

> Am 14.02.2017 um 21:22 schrieb Andreas Kemnade <andreas at kemnade.info>:
> 
> Hi Nikolaus,
> 
> On Tue, 14 Feb 2017 08:51:05 +0100
> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> 
>> Hi Andreas,
>> 
>>> Am 14.02.2017 um 08:01 schrieb Andreas Kemnade
>>> <andreas at kemnade.info>:
>>> 
>>> Hi,
>>> 
>>> On Tue, 14 Feb 2017 04:18:16 +0100
>>> Matthijs van Duin <matthijsvanduin at gmail.com> wrote:
>>> 
>>>> Nikolaus, when I tried to merge my rebased patch branches into
>>>> letux-4.10-rc8 I got a big mess of merge conflicts because you
>>>> merged previous patches from me into it already. Please don't.
>>>> 
>>>> On 10 February 2017 at 11:37, H. Nikolaus Schaller
>>>> <hns at goldelico.com> wrote:
>>>> 
>>>>> It is easy to remove them completely
>>>>> 
>>>> 
>>>> Please do so from your main letux branch while the patches are
>>>> still in development, I'm currently relying on it being a (or
>>>> rather the only) known-working kernel for the pyra which I can use
>>>> to test my patches.
>>>> 
>>> +1
>>> Well, I generated the branch list from the big merge commit and
>>> did a merge myself without that not-ready tiled-fb stuff using the
>>> merge script.
>>> 
>>> But I would favour to be able to just use the letux-4.10-rc8
>>> branches directly without having only a white screen after booting.
>> 
>> Well, in my setup I didn't have a white screen, neither on GTA04 nor
>> on Pyra so I never noticed a problem myself... On GTA04 it works for
>> me while on Pyra I don't get a rotated screen.
>> 
> again still the same.
> 
> [   59.827239] omapdrm omapdrm.0: DMM not available, disable DMM support
> [   59.846588] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> [   59.854705] [drm] No driver support for vblank timestamp query.
> [   59.863464] omapdrm omapdrm.0: Tiled buffers require DMM
> [   59.870483] omapdrm omapdrm.0: failed to allocate buffer object
> [   59.878570] omapdrm omapdrm.0: omap_fbdev_init failed
> [   59.884979] [drm] Initialized omapdrm 1.0.0 20110917 on minor 0

Yes, I also have this.

[   20.875640] omapdrm omapdrm.0: DMM not available, disable DMM support
[   20.883361] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[   20.883361] [drm] No driver support for vblank timestamp query.
[   20.884613] omapdrm omapdrm.0: Tiled buffers require DMM
[   20.884613] omapdrm omapdrm.0: failed to allocate buffer object
[   20.884918] omapdrm omapdrm.0: omap_fbdev_init failed
[   20.885131] [drm] Initialized omapdrm 1.0.0 20110917 on minor 0

> 
> Now I analyzed a bit further.
> There is no framebuffer device like /dev/fb0.
> So no blinking cursor appears in the framebuffer and no other stuff
> works which relies on it (splash pictures and console on framebuffer)
> But what still works is the modesetting xorg driver.

Indeed.

I haven't looked for the framebuffer for a while so I didn't notice
that it is missing completely.

Well, the splash pictures have a different problem in omapdss that
they are tried to be initialized before the omapdss has been set up.
The only solution would be to make everything compiled into the kernel
instead of loadable modules (which depend a little on the DT, e.g. panel
drivers).

> 
>>> 
>>> If that is important for some showcase, merge it on top of
>>> letux-4.10-rc8 to form a pyra-showcase-4.10-rc8 branch
>>> or something like that.
>> 
>> Well, it should not be a special showcase, it should be possible to
>> point pyra and gta04 users to the latest letux kernel w/o making such
>> differences. It is the core philosophy of the letux kernel to support
>> all devices.
>> 
>> If there is a bug we should not fix it by workarounds that users can
>> see and make them trouble. And pointing people to different kernel
>> flavours is not a solution.
>> 
>> So my main goal is to get the Pyra rotated screen working in 4.10-rc9
>> without influencing the GTA04 screen.
>> 
>> That is what we should work on. Not workarounds for either.
>> 
> IMHO,
> in patch
> XXX omapdrm: allocate fbdev in TILER
> there has to be a
> if (!pyra) {

yes, looks good. Should be if (omap3()) {

because I think omap4 and omap5 both have the TILER.

If you find a patch that makes it work, I can add it.

> ...
> } else {
> + new stuff
> + ...
> }
> 
> instead of the
> #if 0
> 
> ...
> #else
> + new stuff
> + ...
> #endif
> 
> Regards,
> Andreas

BR,
Nikolaus


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