BUG Beaglebone HDMI output flickers

["Radek Dostál" <radek.dostal@streamunlimited.com>]

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Dear All,

Beaglebone black display starts to flicker after updating our userspace 
to GStreamer 1.6 and decoding WMA. We analyzed the change in gstreamer 
and created simple program, which allow us to reproduce the issue 
reliably - see attached.

When attached program mem-test.c is executed with nice as user nobody, 
it is still causing heavy flickering of the BeagleBone HDMI output. You 
can see the example on this 30second video https://db.tt/ZQf4nq9A

Following messages are printed to the kernel log:
[  450.997625] tilcdc 4830e000.lcdc: tilcdc_crtc_irq(0x00000020): FIFO
underfow
[  451.023380] tilcdc 4830e000.lcdc: tilcdc_crtc_irq(0x00000020): FIFO
underfow
[  451.032606] tilcdc 4830e000.lcdc: tilcdc_crtc_irq(0x00000020): FIFO
underfow
[  451.056635] tilcdc 4830e000.lcdc: tilcdc_crtc_irq(0x00000020): FIFO
underfow
[  451.065265] tilcdc 4830e000.lcdc: tilcdc_crtc_irq(0x00000020): FIFO
underfow

What is very interesting only some sizes of memtest are causing flickering:

Sizes 0 to 24: no flickering.
Sizes 25 to 2072: heavy flickering:
Sizes 2073 to 2200: a little bit of flickering:

Any help would be greatly appreciated,
Radek Dostal



[-- Attachment #2: mem-test.c --]
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#include <string.h>
#include <stdint.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
        int size;
        uint8_t *memblock;

        if (argc < 2)
                return -1;

        size = atoi(argv[1]);

        memblock = malloc(size);

        while (1)
        {
                memset(memblock, 0, size);
        }

        free(memblock);

        return 0;
}

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