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AM335x tilcdc FIFO Underflow

Michael Liesenberg85
Mastermind 7560 points

Hi there,

i am using the Beaglebone Black with a 10.1'' 1280x800 Display.

When i play a video or so i am getting a message on the UART :

tilcdc 4830e000.lcdc: tilcdc_crtc_irq(0x00000004): Sync lost

tilcdc 4830e000.lcdc: tilcdc_crtc_irq(0x00000020): FIFO underfow

And the Display looks like is ajusting it self or going on and off very fast.

On a reboot or when the system boot up i get this message:

of_graph_get_next_endpoint(): no port node found in /ocp/lcdc@4830e000

I think the DDR rate is too slow?

Any idea?

  • 0
    TI__Guru**** 393215 points
    Hi,

    What Linux version are you using? What is the video format? Is this display connected to the HDMI port or is it a parallel LCD?
  • 0 in reply to Biser Gatchev-XID
    Mastermind 7560 points
    Hi Biser,

    i am using the latest Debian Jessie Image from beagleboard.com
    The Display is connected to the RGB parallel Pins.

    And it isnt only about the video but if i display many frames on the display i get the same problem.

    My Display settings and timings are as followed:
    panel {
    status = "okay";
    compatible = "ti,tilcdc,panel";
    pinctrl-names = "default";
    pinctrl-0 = <&bb_lcd_lcd_pins>;
    panel-info {
    ac-bias = <255>;
    ac-bias-intrpt = <0>;
    dma-burst-sz = <16>;
    bpp = <32>;
    fdd = <0x80>;
    tft-alt-mode = <0>;
    stn-565-mode = <0>;
    mono-8bit-mode = <0>;
    sync-edge = <0>;
    sync-ctrl = <1>;
    raster-order = <0>;
    fifo-th = <0>;
    };
    display-timings {
    native-mode = <&timing0>;
    timing0: 1280x800 {
    clock-frequency = <70000000>;
    hactive = <1280>;
    vactive = <800>;
    hfront-porch = <80>;
    hback-porch = <60>;
    hsync-len = <20>;
    vback-porch = <12>;
    vfront-porch = <8>;
    vsync-len = <3>;
    hsync-active = <0>;
    vsync-active = <0>;
    };
    };
    };


    If i dont use much of the display i dont get any erros or strange behaviors.
    The size and colors are correct so i supose the timings are also correct.
  • 0 in reply to Michael Liesenberg85
    TI__Guru**** 393215 points
    I'm sorry, this forum supports only the TI distributed Linux SDK. All other versions are supported by the community at beagleboard.org/.../Forums However I would suggest that you check your timings against the display requirements. Especially the pixel clock 70MHz seems low to me to support 1280x800 resolution at 60Hz.
  • 0 in reply to Biser Gatchev-XID
    Mastermind 7560 points
    Ok i just wrote to them now,

    i checked the display datasheet and 73.4 MHz is the maximum.

    Thank you,

    Michael
  • 0 in reply to Michael Liesenberg85
    TI__Guru**** 393215 points
    The type of error reported suggests that the fuf_en_clr interrupt fires (AM335X TRM Rev. M section 13.5.1.23). You might need to use a larger value for th_fifo_ready (AM335X TRM Rev. M section 13.5.1.16), however I'm not a software expert and cannot say where this should be set.