Re: [PATCH 3/4] drm: Add helper for simple display pipeline

Noralf Trønnes
2016-05-09T18:37:44Z

Den 09.05.2016 16:46, skrev Daniel Vetter:
> On Thu, May 05, 2016 at 03:24:33PM +0200, Noralf Trønnes wrote:
>> Provides helper functions for drivers that have a simple display
>> pipeline. Plane, crtc and encoder are collapsed into one entity.
>>
>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
>> +static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>> + struct drm_plane_state *pstate)
>> +{
>> + struct drm_simple_display_pipe *pipe;
>> + struct drm_crtc_state *cstate;
>> +
>> + pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>> + if (!pipe->funcs || !pipe->funcs->check)
>> + return 0;
>> +
>> + cstate = drm_atomic_get_existing_crtc_state(pstate->state,
>> + &pipe->crtc);
>> +
>> + return pipe->funcs->check(pipe, pstate, cstate);
>> +}
> Ok one thing I've missed here is that for most drivers this is way too
> simple a check function, which means we'll end up with tons of duplicated
> code. Things which the drm core allows, but simple pipelines all don't
> really cope with:
> - plane scaling
> - disabling the plane without the crtc (i.e. scan out black)
> - plane not sized to fill the entire hactive/vactive
>
> There's a helper to do most of these checks for you -
> drm_plane_helper_check_update. I think it'd be good to place a call for
> that in here, before we call down into the driver's ->check callback. But
> ofc before we return 0; we want these checks always done. And catch all
> these things so that drivers never fall over this pitfall.

Does this resemble what you're after? I'm just guessing here.

static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
struct drm_plane_state *pstate)
{
struct drm_rect src = {
.x1 = pstate->src_x,
.y1 = pstate->src_y,
.x2 = pstate->src_x + pstate->src_w,
.y2 = pstate->src_y + pstate->src_h,
};
struct drm_rect dest = {
.x1 = pstate->crtc_x,
.y1 = pstate->crtc_y,
.x2 = pstate->crtc_x + pstate->crtc_w,
.y2 = pstate->crtc_y + pstate->crtc_h,
};
struct drm_rect clip = { 0 };
struct drm_simple_display_pipe *pipe;
struct drm_crtc_state *cstate;
bool visible;
int ret;

pipe = container_of(plane, struct drm_simple_display_pipe, plane);
clip.x2 = pipe->crtc.mode.hdisplay;
clip.y2 = pipe->crtc.mode.vdisplay;
ret = drm_plane_helper_check_update(plane, &pipe->crtc, plane->fb,
&src, &dest, &clip,
DRM_PLANE_HELPER_NO_SCALING,
DRM_PLANE_HELPER_NO_SCALING,
false, false, &visible);
if (ret)
return ret;

/* How to handle !visible, is it even possible? */

if (!pipe->funcs || !pipe->funcs->check)
return 0;

cstate = drm_atomic_get_existing_crtc_state(pstate->state,
&pipe->crtc);

return pipe->funcs->check(pipe, pstate, cstate);
}

Noralf.

> Noticed while discussing tilcdc atomic patches, since tilcdc could
> probably use drm_simple_display_pipe too.
> -Daniel