Re: [PATCH 2/2] OMAPDSS: APPLY: make ovl_enable/disable synchronous

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On Wed, 2012-02-29 at 10:13 +0000, Florian Tobias Schandinat wrote:
> On 02/29/2012 08:48 AM, Tomi Valkeinen wrote:
> > ovl->enable/disable are meant to be synchronous so that they can handle
> > the configuration of fifo sizes. The current kernel doesn't configure
> > fifo sizes yet, and so the code doesn't need to block to function (from
> > omapdss driver's perspective).
> > 
> > However, for the users of omapdss a non-blocking ovl->disable is
> > confusing, because they don't know when the memory area is not used
> > any more.
> > 
> > Furthermore, when the fifo size configuration is added in the next merge
> > window, the change from non-blocking to blocking could cause side
> > effects to the users of omapdss. So by making the functions block
> > already will keep them behaving in the same manner.
> 
> Is there any difference to doing it now?
> I agree that this should be fixed but if we can't avoid breaking users I'd
> prefer to break them in a merge window not in late rc stage. Or did we introduce
> these functions just in the last merge window?

Yes, these were introduced in the merge window. And I explicitly said
the functions are blocking so that they can perform their job. And just
to clarify, the functions already use a mutex, so in that sense they are
blocking. They just don't currently wait until the HW has finished with
the overlay.

The problem was raised by Rob Clark, who's writing the omapdrm driver,
as he doesn't have a way to ensure that the overlay has been truly
disabled and the memory is is no longer in use.

(I forgot to cc him for the patch, adding him now).

 Tomi


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