[Intel-gfx] [PATCH 2/4] drm/i915: Asynchronously perform the set-base for a simple modeset

[Rodrigo Vivi]

For me this patch makes sense and swith to fbcon is faster, so:

Reviewed-by: Rodrigo Vivi <rodrigo.vivi at gmail.com>

with this -collector is "empty"... at least until next -testing update.

On Mon, Oct 7, 2013 at 5:15 PM, Rodrigo Vivi <rodrigo.vivi at gmail.com> wrote:
> From: Chris Wilson <chris at chris-wilson.co.uk>
>
> A simple modeset, where we only wish to switch over to a new framebuffer
> such as the transition from fbcon to X, takes around 30-60ms. This is
> due to three factors:
>
> 1. We need to make sure the fb->obj is in the display domain, which
> incurs a cache flush to ensure no dirt is left on the scanout.
>
> 2. We need to flush any pending rendering before performing the mmio
> so that the frame is complete before it is shown.
>
> 3. We currently wait for the vblank after the mmio to be sure that the
> old fb is no longer being shown before releasing it.
>
> (1) can only be eliminated by userspace preparing the fb->obj in advance
> to already be in the display domain. This can be done through use of the
> create2 ioctl, or by reusing an existing fb->obj.
>
> However, (2) and (3) are already solved by the existing page flip
> mechanism, and it is surprisingly trivial to wire them up for use in the
> set-base fast path. Though it can be argued that this represents a
> subtle ABI break in that the set_config ioctl now returns before the old
> framebuffer is unpinned. The danger is that userspace will start to
> modify it before it is no longer being shown, however we should be able
> to prevent that through proper domain tracking.
>
> By combining all of the above, we can achieve an instaneous set_config:
>
> [     6.601] (II) intel(0): switch to mode 2560x1440 at 60.0 on pipe 0 using DP2, position (0, 0), rotation normal
> [     6.601] (II) intel(0): Setting screen physical size to 677 x 381
>
> v2 (by Vivi): page_flip_flag was added to intel_crtc_page_flip
>               in a previous commit. using 0.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi at gmail.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index b9cede7..bc47f1e 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -9569,10 +9569,13 @@ static int intel_crtc_set_config(struct drm_mode_set *set)
>                 ret = intel_set_mode(set->crtc, set->mode,
>                                      set->x, set->y, set->fb);
>         } else if (config->fb_changed) {
> -               intel_crtc_wait_for_pending_flips(set->crtc);
> -
> -               ret = intel_pipe_set_base(set->crtc,
> -                                         set->x, set->y, set->fb);
> +               if (to_intel_framebuffer(set->fb)->obj->ring == NULL ||
> +                   save_set.x != set->x || save_set.y != set->y ||
> +                   intel_crtc_page_flip(set->crtc, set->fb, NULL, 0)) {
> +                       intel_crtc_wait_for_pending_flips(set->crtc);
> +                       ret = intel_pipe_set_base(set->crtc,
> +                                                 set->x, set->y, set->fb);
> +               }
>         }
>
>         if (ret) {
> --
> 1.8.1.4
>



-- 
Rodrigo Vivi
Blog: http://blog.vivi.eng.br