Re: wait_event_timeout() usage in decon_wait_for_vblank()

[Inki Dae]

Hi,

2025년 2월 1일 (토) 오전 1:56, Bjorn Helgaas <helgaas@xxxxxxxxxx>님이 작성:
>
> I don't know this code at all, so this is likely just noise, but the
> wait_event_timeout() usage in decon_wait_for_vblank() looks funny to
> me.
>
> decon_wait_for_vblank() waits on wait_vsync_queue for wait_vsync_event
> to be cleared.
>
> But decon_irq_handler() only clears wait_vsync_event and wakes up
> wait_vsync_queue when !ctx->i80_if.
>
> I don't see any i80_if connection in decon_wait_for_vblank().  Does
> the wait always time out if i80_if is set?  Is there some reason we
> don't use decon_wait_for_vblank() at all if i80_if is set?
>

For the decon series, the implementation for the i80 interface has not
yet been completed. If you would like to see how the i80 interface is
handled in Exynos, please refer to the code for the legacy display
controller module, exynos_drm_fimd.c, available at the following link:
https://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos.git/tree/drivers/gpu/drm/exynos/exynos_drm_fimd.c?h=exynos-drm-fixes#n1053

Furthermore, please note that within the decon driver, prior to
creating the CRTC, it is necessary to implement the TE handler for the
i80 interface in the te_handler of exynos_drm_crtc_ops and register it
as a callback.

Thanks,
Inki Dae

> Bjorn
>