Re: [PATCH RFC] drm/crtc_helper: Add drm_crtc_helper_disable_planes()

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Nov 20, 2015 at 12:03:41PM +0200, Jyri Sarha wrote:
> Add drm_crtc_helper_disable_planes() for disabling all planes
> associated with the given CRTC and having disable callback. This can
> be used for instance in CRTC helper disable callback.
> 
> Signed-off-by: Jyri Sarha <jsarha@ti.com>
> ---
> So it appears that this is the only missing piece for disabling and
> enabling planes with their associated CRTCs for the times when the
> CRTCs are blanked or otherwise unused.
> 
>  drivers/gpu/drm/drm_crtc_helper.c | 26 ++++++++++++++++++++++++++
>  include/drm/drm_crtc_helper.h     |  1 +
>  2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
> index ef53475..33dddd5 100644
> --- a/drivers/gpu/drm/drm_crtc_helper.c
> +++ b/drivers/gpu/drm/drm_crtc_helper.c
> @@ -410,6 +410,32 @@ done:
>  }
>  EXPORT_SYMBOL(drm_crtc_helper_set_mode);
>  
> +/**
> + * drm_crtc_helper_disable_planes - helper to disable CRTC's planes
> + * @crtc: CRTC
> + *
> + * Disables all planes associated with the given CRTC and having
> + * disable callback. This can be used for instance in CRTC helper

s/in CRTC/in the CRTC/


> + * disable callback.

"... to disable all planes before shutting down the display pipeline."
just to clarify usage.

One open is whether we should call the crtc-level atomic_begin/flush
functions. I think adding that would be good, to avoid tearing while
disabling planes. If drivers need different behaviour we can always add a
knob to select the right one (i.e. with or without atomic_begin/flush).

> + */
> +void drm_crtc_helper_disable_planes(struct drm_crtc *crtc)

This function only makes sense for atomic drivers, so should be in
drm_atomic_helper.c. drm_crtc_helper.c is the legacy helper library for
non-atomic drivers.

Also needs a different name then, for example
drm_atomic_helper_disable_planes_on_crtc, for consistency with
drm_atomic_helper_commit_planes_on_crtc

> +{
> +	struct drm_plane *plane;
> +	int i;
> +
> +	drm_for_each_plane(plane, crtc->dev) {
> +		const struct drm_plane_helper_funcs *plane_funcs =
> +			plane->helper_private;
> +
> +		if (plane->state->crtc != crtc || !plane_funcs)
> +			continue;
> +
> +		if (plane_funcs->atomic_disable)
> +			plane_funcs->atomic_disable(plane, NULL);

Imo WARN_ON(!plane_funcs->atomic_disable); since calling this function
without having disable hooks really doesn't make sense. Please also update
the kerneldoc with something like "It is a bug to call this function
without having implemented the ->atomic_disable() plane hook."

Cheers, Daniel

> +	}
> +}
> +EXPORT_SYMBOL(drm_crtc_helper_disable_planes);
> +
>  static void
>  drm_crtc_helper_disable(struct drm_crtc *crtc)
>  {
> diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
> index 3febb4b..d47051f 100644
> --- a/include/drm/drm_crtc_helper.h
> +++ b/include/drm/drm_crtc_helper.h
> @@ -189,6 +189,7 @@ extern bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
>  				     struct drm_display_mode *mode,
>  				     int x, int y,
>  				     struct drm_framebuffer *old_fb);
> +extern void drm_crtc_helper_disable_planes(struct drm_crtc *crtc);
>  extern bool drm_helper_crtc_in_use(struct drm_crtc *crtc);
>  extern bool drm_helper_encoder_in_use(struct drm_encoder *encoder);
>  
> -- 
> 1.9.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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