On 14.01.13 17:05, Thierry Reding wrote:
> Implement support for the VBLANK IOCTL. Note that Tegra is somewhat
> special in this case because it doesn't use the generic IRQ support
> provided by the DRM core (DRIVER_HAVE_IRQ) but rather registers one
> interrupt handler for each display controller.
>
> While at it, clean up the way that interrupts are enabled to ensure
> that the VBLANK interrupt only gets enabled when required.
>
> Signed-off-by: Thierry Reding <thierry.reding at avionic-design.de>
... snip ...
> struct drm_driver tegra_drm_driver = {
> .driver_features = DRIVER_BUS_PLATFORM | DRIVER_MODESET | DRIVER_GEM,
> .load = tegra_drm_load,
> @@ -96,6 +136,10 @@ struct drm_driver tegra_drm_driver = {
> .open = tegra_drm_open,
> .lastclose = tegra_drm_lastclose,
>
> + .get_vblank_counter = drm_vblank_count,
-> .get_vblank_counter = drm_vblank_count is a no-op.
.get_vblank_counter() is supposed to return some real hardware vblank
counter value to reinitialize the software vblank counter at vbl irq
enable time. That software counter gets queried via drm_vblank_count().
If you hook this up to drm_vblank_count() it essentially returns a
constant, frozen vblank count, it has the same effect as returning zero
or any other constant value -- You lose all vblank counter increments
during vblank irq off time. The same problem is present in nouveau-kms.
I think it would be better to either implement a real hw counter query,
or some function with a /* TODO: Implement me properly */ comment which
returns zero, so it is clear something is missing here.
thanks,
-mario
> + .enable_vblank = tegra_drm_enable_vblank,
> + .disable_vblank = tegra_drm_disable_vblank,
> +
> .gem_free_object = drm_gem_cma_free_object,
> .gem_vm_ops = &drm_gem_cma_vm_ops,
> .dumb_create = drm_gem_cma_dumb_create,
> diff --git a/drivers/gpu/drm/tegra/drm.h b/drivers/gpu/drm/tegra/drm.h
