Re: [PATCH 5/5] drm/atomic-helpers: make mode_set hooks optional

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Daniel,

On Sunday 22 February 2015 19:53:23 Laurent Pinchart wrote:
> On Sunday 22 February 2015 12:24:20 Daniel Vetter wrote:
> > With runtime PM the hw might still be off while doing the ->mode_set
> > callbacks - runtime PM get/put should only happen in the
> > enable/disable hooks to properly support DPMS. Which essentially makes
> > these callbacks useless for drivers support runtime PM, so make them
> > optional. Again motivated by discussions with Laurent.
> > 
> > Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> 
> I think we should go one step further and remove .mode_set() completely for
> drivers converted to atomic updates. There are two cases to consider:
> 
> - Drivers that implement runtime PM can't use the .mode_set() callback for
> the reason explained above. Those drivers will thus not implement
> .mode_set() and will perform mode setting related hardware configuration in
> .enable().
> 
> - Drivers that don't implement runtime PM (we probably want to discourage
> this globally, but that's a different topic) can use the .mode_set()
> callbacks, but they could equally well perform mode setting in .enable() as
> the runtime PM- enabled drivers, without any drawback.
> 
> To increase consistency, I thus believe we should get rid of .mode_set()
> completely for drivers converted to atomic updates.

On second thought, I've confused .mode_set() and .mode_set_nofb(). .mode_set() 
still makes sense for encoders, but the above reasoning should apply in my 
opinion for the CRTC .mode_set_nofb().

> However, this patch is good as a first step, so if you want to apply it
> already,
> 
> Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 
> > ---
> > 
> >  drivers/gpu/drm/drm_atomic_helper.c | 5 +++--
> >  include/drm/drm_crtc_helper.h       | 3 ++-
> >  2 files changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c
> > b/drivers/gpu/drm/drm_atomic_helper.c index 9fd3466bf277..5e10bcb7d98d
> > 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -723,7 +723,7 @@ crtc_set_mode(struct drm_device *dev, struct
> > drm_atomic_state *old_state)
> > 
> >  		funcs = crtc->helper_private;
> > 
> > -		if (crtc->state->enable) {
> > +		if (crtc->state->enable && funcs->mode_set_nofb) {
> > 
> >  			DRM_DEBUG_ATOMIC("modeset on [CRTC:%d]\n",
> >  			
> >  					 crtc->base.id);
> > 
> > @@ -759,7 +759,8 @@ crtc_set_mode(struct drm_device *dev, struct
> > drm_atomic_state *old_state) * Each encoder has at most one connector
> > (since we always steal * it away), so we won't call call mode_set hooks
> > twice.
> > 
> >  		 */
> > 
> > -		funcs->mode_set(encoder, mode, adjusted_mode);
> > +		if (funcs->mode_set)
> > +			funcs->mode_set(encoder, mode, adjusted_mode);
> > 
> >  		if (encoder->bridge && encoder->bridge->funcs->mode_set)
> >  		
> >  			encoder->bridge->funcs->mode_set(encoder->bridge,
> > 
> > diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
> > index c250a22b39ab..92d5135b55d2 100644
> > --- a/include/drm/drm_crtc_helper.h
> > +++ b/include/drm/drm_crtc_helper.h
> > @@ -89,6 +89,7 @@ struct drm_crtc_helper_funcs {
> > 
> >  	int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
> >  	
> >  			struct drm_display_mode *adjusted_mode, int x, int y,
> >  			struct drm_framebuffer *old_fb);
> > 
> > +	/* Actually set the mode for atomic helpers, optional */
> > 
> >  	void (*mode_set_nofb)(struct drm_crtc *crtc);
> >  	
> >  	/* Move the crtc on the current fb to the given position *optional* 
*/
> > 
> > @@ -119,7 +120,7 @@ struct drm_crtc_helper_funcs {
> > 
> >   * @mode_fixup: try to fixup proposed mode for this connector
> >   * @prepare: part of the disable sequence, called before the CRTC modeset
> >   * @commit: called after the CRTC modeset
> > 
> > - * @mode_set: set this mode
> > + * @mode_set: set this mode, optional for atomic helpers
> > 
> >   * @get_crtc: return CRTC that the encoder is currently attached to
> >   * @detect: connection status detection
> >   * @disable: disable encoder when not in use (overrides DPMS off)

-- 
Regards,

Laurent Pinchart

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