[PATCH] drm: hdlcd: allow HDLCD to be used without interrupt

[Russell King - ARM Linux]

On Wed, Aug 30, 2017 at 11:54:14AM +0100, Liviu Dudau wrote:
> On Tue, Aug 29, 2017 at 05:48:24PM +0100, Russell King - ARM Linux wrote:
> > On Tue, Aug 29, 2017 at 02:33:52PM +0100, Liviu Dudau wrote:
> > > I've worked with Vladimir Murzin inside ARM to try to sort out problems
> > > on the board like the one that you have. He's got to a point where the HDLCD
> > > starts correctly after adding a non-fixed pxlclk source, but then the rest of
> > > the setup is semi-useless without a working IRQ because DRM atomic calls
> > > will give you a vblank timeout splat everytime you invoke them. So I'm
> > > not sure how you want to progress with this patch, as not having an IRQ
> > > line means you will not get any vblank interrupts and you can't use the
> > > driver with userspace that calls DRM API.
> > > 
> > > The RTL guys are apparently working on a fix, but I have no ETA or
> > > details on when they are going to do.
> > 
> > It sounds then like this patch doesn't make sense - so I'm happy
> > for it to be dropped.  It's something to bear in mind in the future
> > when folk decide whether to adopt fbdev or DRM support for hardware
> > that gets used in MMU-less hardware...
> 
> I don't think this has anything to do with the presence of a MMU or not.

It doesn't directly, but nommu is probably more likely to not wire the
interrupt than mmu systems, on the grounds that nommu is more embedded.

-- 
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