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Could DM8168 HDVPSS raise an interrupt or event when framebuffer data send out to LCD completed?

Jed ZHU
Intellectual 815 points

Hi experts,

We want to raise an interrupt when framebuffer data send completed, e.g. framefuffer-to-LCD DMA TxFIFO empty interrupt.

Now it is implemented by VPSS M3, so from VPSS framebuffer driver side, is it possible to capture this event?

Thanks in advance.

Jed ZHU

  • 0
    TI__Mastermind 20245 points

    Hi,

    There is no such interrupt possible. But you can use FBIO_WAITFORVSYNC ioctl to make sure that your frame has been submitted to hardware for display.

    Regards,

    Hardik Shah

  • 0 in reply to HardikShah
    Intellectual 815 points

    Hi Hardik Shah,

    Thank you for reply.

    Yes, FBIO_WAITFORVSYNC ioctl will make the kernel put the process to sleep until VSYNC interrupt occurs, but our LCD uses Data Enable signal to drive itself, VSYNC and HSYNC are nerver used, so could we use FBIO_WAITFORVSYNC ioctl?

    And the 2nd issue is how does C674x+ DSP capture this event? Could it get such information from HDVPSS dirrectly instead of from Cortex-A8 (Linux FB driver)?

    Best regards,

    Jed ZHU

  • 0 in reply to HardikShah
    Intellectual 815 points

    And I check the source code of omap FB driver, it seems FBIO_WAITFORVSYNC doesn't work now, is it possible to use OMAPFB_WAITFORVSYNC instead?

    Ln.772, omapfb_ioctl(), of /ti-ezsdk_dm816x-evm_5_03_01_15/board-support/linux-2.6.37-psp04.00.01.13.patch2/drivers/video/omap2/omapfb/omapfb-ioctl.c

            case FBIO_WAITFORVSYNC:
                    if (get_user(p.crt, (__u32 __user *)arg)) {
                            r = -EFAULT;
                            break;
                    }
                    if (p.crt != 0) {
                            r = -ENODEV;
                            break;
                    }
                    /* FALLTHROUGH */

            case OMAPFB_WAITFORVSYNC:
                    DBG("ioctl WAITFORVSYNC\n");
                    if (!display) {
                            r = -EINVAL;
                            break;
                    }

                    r = display->manager->wait_for_vsync(display->manager);
                    break;

  • 0 in reply to Jed ZHU
    TI__Guru 65610 points

    You were refering OMAP FBDev source codes, which does not match your HW platform. Please check TI81XX FBdev driver under drivers/video/ti81xx/ti81xxfb/ti81xxfb-ioctl.c/

    FBIO_WAITFORVSYNC is the right one to use.

    Regards,

    yihe

  • 0 in reply to yihe
    Intellectual 815 points

    Thanks Yihe, I also found the exact source codes.

    I checked the implementation of FBIO_WAITFORVSYNC, it is invoked in vps_grpx_vsync_cb(), in drivers/video/ti81xx/vpss/grpx.c, it is a callback register to VPSSM3 VSYNC ISR, so is it possible to send a notify to C674x DSP via SYS/Link in it, similar with VSYNC interrupt to DSP?

     

    Best regards,

    Jed ZHU