On Sun, Feb 02, 2025 at 01:02:47PM +0900, Inki Dae wrote: > 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. I'll take your word for it that this all works as intended. For many wait_event_timeout() callers, the connection between kicking off some operation, waiting for completion, and doing the wakeup is a little bit obscure and hard to analyze without deep knowledge of the driver. This was just one instance of those. Bjorn
