[Q] tilcdc: cannot allocate buffer

[Rob Clark]

On Fri, Mar 14, 2014 at 7:24 AM, Robert Kuhn <robert at ku.hn> wrote:
> Hi,
>
> using the code from
> https://github.com/dvdhrm/docs/blob/master/drm-howto/modeset-vsync.c
> on my beaglebone black I get sometimes this error:
>
> [ 7772.673057] tilcdc 4830e000.lcdc: failed to allocate buffer with size
> 5242880
> [ 7777.663102] tilcdc 4830e000.lcdc: failed to allocate buffer with size
> 5242880
> [ 7783.892790] tilcdc 4830e000.lcdc: failed to allocate buffer with size
> 5242880
>
> When I restart the programm usually everything works as expected. What is
> the couse of this error?
>

tilcdc uses a CMA pool for buffer allocation (because it needs
physically contiguous buffers).  You just need to bump up the pool
size.  In some cases the driver could be holding a reference to a
buffer until slightly after userspace frees it (ie. until next
vblank), my guess is that you are occasionally hitting that scenario
and until that buffer is freed there is not enough remaining in the
CMA carveout to allocate an additional buffer.

BR,
-R

>
>
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