[mythtv] fixes/31 branch created!

[Piotr Oniszczuk]

> Wiadomość napisana przez Mike Bibbings <mike.bibbings at gmail.com> w dniu 10.03.2020, o godz. 13:57:
> 
> Hi Mark,
> 
> Latest version v32-Pre-151-g4e81d4b52b  working well on Pi4.
> 
> On a Pi2 I am seeing from time to time - it is fatal, and it needs a reboot to resolve.
> 
> [ 4067.968745] [drm:vc4_bo_create [vc4]] *ERROR* Failed to allocate from CMA:
> [ 4067.968765] [drm]                            V3D: 158964kb BOs (1142)
> [ 4067.968771] [drm]                     V3D shader:     84kb BOs (21)
> [ 4067.968778] [drm]                           dumb:   8116kb BOs (2)
> [ 4067.968783] [drm]                         binner:  16384kb BOs (1)
> [ 4067.968789] [drm]                total purged BO:  21216kb BOs (112)
> [ 4067.970319] [drm:vc4_bo_create [vc4]] *ERROR* Failed to allocate from CMA:
> [ 4067.970333] [drm]                            V3D: 151216kb BOs (1114)
> [ 4067.970339] [drm]                     V3D shader:     84kb BOs (21)
> [ 4067.970343] [drm]                           dumb:   8116kb BOs (2)
> [ 4067.970349] [drm]                         binner:  16384kb BOs (1)
> [ 4067.970354] [drm]                total purged BO:  21216kb BOs (112)
> [ 4067.981562] [drm:vc4_bo_create [vc4]] *ERROR* Failed to allocate from CMA:
> [ 4067.981577] [drm]                            V3D: 151216kb BOs (1114)
> [ 4067.981583] [drm]                     V3D shader:     84kb BOs (21)
> [ 4067.981588] [drm]                           dumb:   8116kb BOs (2)
> [ 4067.981595] [drm]                         binner:  16384kb BOs (1)
> [ 4067.981601] [drm]                total purged BO:  21216kb BOs (112)
> [ 4068.076587] [drm:vc4_bo_create [vc4]] *ERROR* Failed to allocate from CMA:
> [ 4068.076607] [drm]                            V3D: 159380kb BOs (1116)
> [ 4068.076613] [drm]                     V3D shader:     84kb BOs (21)
> [ 4068.076620] [drm]                           dumb:   8116kb BOs (2)
> [ 4068.076627] [drm]                total purged BO:  31516kb BOs (174)
> [ 4068.076642] vc4_v3d 3fc00000.v3d: Failed to allocate memory for tile binning: -12. You may need to enable CMA or give it more memory.
> 
> Note this is using mythfrontend only  to a remote backend.
> 
> Have you or anyone else seen this ?
> 

looks to me like kernel has too smal CMA to operate with video playback.
cma is needed as video frames decoded by decoder and passed to 3D engine needs continues memory regions (rpi iirc don’t have IOMMU to help here)
may you pls try do add in config.txt i.e. 
cma=256 (or 384)
and see how it goes?