Re: [PATCH] omap2+: add drm device

Rob Clark
2012-05-24T08:44:31Z

On Thu, May 24, 2012 at 1:21 AM, Tomi Valkeinen <tomi.valkeinen@ti.com> wrote:
> On Thu, 2012-05-24 at 10:05 +0300, Tomi Valkeinen wrote:
>> On Thu, 2012-05-24 at 00:27 -0600, Clark, Rob wrote:
>> > On Thu, May 24, 2012 at 12:01 AM, Tomi Valkeinen <tomi.valkeinen@ti.com> wrote:
>> > > Hi,
>> > >
>> > > On Wed, 2012-05-23 at 15:08 -0500, Andy Gross wrote:
>> > >> Register OMAP DRM/KMS platform device.  DMM is split into a
>> > >> separate device using hwmod.
>> > >>
>> > >> Signed-off-by: Andy Gross <andy.gross@ti.com>
>> > >
>> > > <snip>
>> > >
>> > >> +static int __init omap_init_drm(void)
>> > >> +{
>> > >> +     struct omap_hwmod *oh = NULL;
>> > >> +     struct platform_device *pdev;
>> > >> +
>> > >> +     /* lookup and populate the DMM information, if present - OMAP4+ */
>> > >> +     oh = omap_hwmod_lookup("dmm");
>> > >> +
>> > >> +     if (oh) {
>> > >> +             pdev = omap_device_build(oh->name, -1, oh, NULL, 0, NULL, 0,
>> > >> +                                     false);
>> > >> +             WARN(IS_ERR(pdev), "Could not build omap_device for %s\n",
>> > >> +                     oh->name);
>> > >> +     }
>> > >> +
>> > >> +     return platform_device_register(&omap_drm_device);
>> > >> +
>> > >> +}
>> > >
>> > > I still don't like fixing the tiler to drm. I would like to have basic
>> > > tiler support in omapfb also, but with this approach I'll need to
>> > > duplicate the code. And even if we disregard omapfb, wouldn't it be
>> > > architecturally better to have the tiler as a separate independent
>> > > library/driver?
>> >
>> > Not easily, at least not if we want to manage to use tiler/dmm in a
>> > more dynamic way, or to enable some additional features which are
>> > still on the roadmap (like reprogramming dmm synchronized w/ scanout,
>> > or some things which are coming if future hw generations).  We need
>> > one place to keep track of which buffers are potentially evictable to
>> > make room for mapping a new buffer.  And if you look at the tricks
>> > that go on with mmap'ing tiled buffers to userspace, you *really*
>> > don't want to duplicate that in N different drivers.
>>
>> So why can't all that code be in a tiler library/driver?
>
> And I think we've discussed about this before, so sorry if I'm repeating
> myself. I just find it odd that we are not able to create a nice
> separate lib/driver for the tiler, which is a separate piece of HW that
> multiple drivers might want to use.

but other drivers *can* use tiler, thanks to dmabuf.. I have omap4iss
v4l2 camera working w/ tiler buffers on my pandaboard, for example.

Maybe fbdev is an exception to the rule because it has no way for
userspace to pass it a buffer to use. But on the other hand it is a
legacy API so I'm not sure if it is worth loosing too much sleep over
that.

BR,
-R

>  Tomi
>
>
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