[Intel-gfx] [PATCHv4 1/3] drm/i915: Make finding unused crtc as a generic function

R, Durgadoss durgadoss.r at intel.com
Mon May 9 09:45:49 UTC 2016



> -----Original Message-----
> From: Ander Conselvan De Oliveira [mailto:conselvan2 at gmail.com]
> Sent: Friday, May 6, 2016 6:38 PM
> To: R, Durgadoss <durgadoss.r at intel.com>; intel-gfx at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCHv4 1/3] drm/i915: Make finding unused crtc as
> a generic function
> 
> On Mon, 2016-04-18 at 19:01 +0530, Durgadoss R wrote:
> > Looping over the crtc list and finding an unused crtc has other users
> > like upfront link training. Hence move it to
> 
> "will have", since this patch precedes the upfront link training one.
> 
> > a common function to re-use the logic.
> >
> > v4:
> > * Added ERR_PTR as a return value in kernel Doc comment (Ander)
> > v3:
> > * Added kernel Doc and removed an invalid comment (Ander)
> > * Rebased on top of latest code which includes locking
> >   for state->enable usage.
> > v2:
> > * Made this as a separate function instead of having it
> >   inside upfront link train code.
> >
> > Signed-off-by: Durgadoss R <durgadoss.r at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 74
> > +++++++++++++++++++++------------
> > ---
> >  drivers/gpu/drm/i915/intel_drv.h     |  2 +
> >  2 files changed, 45 insertions(+), 31 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > b/drivers/gpu/drm/i915/intel_display.c
> > index 4cca155..a6df48b 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -10404,6 +10404,43 @@ static int
> > intel_modeset_setup_plane_state(struct
> > drm_atomic_state *state,
> >  	return 0;
> >  }
> >
> > +/**
> > + * intel_get_unused_crtc - Find an unused crtc for the given encoder
> > + * @encoder: drm_encoder structure
> > + * @ctx: ctx pointer to use with locking
> > + *
> > + * This function tries to find an unused crtc that can drive
> > + * the given encoder. Returns NULL or ERR_PTR on failure.
> 
> This NULL or ERR_PTR makes for an awkward interface. I wonder if it should
> just return ERR_PTR(-EBUSY) or even ERR_PTR(-EINVAL) if there is no free
> crtc. It's no big deal though.
> 
> Also, in the success case crtc->mutex is kept locked. That should be added to
> the documentation above.
>

Ok, Will make the failure case as return (-EINVAL).
 
> > + */
> > +struct drm_crtc *intel_get_unused_crtc(struct drm_encoder *encoder,
> > +				struct drm_modeset_acquire_ctx *ctx) {
> > +	struct drm_crtc *possible_crtc;
> > +	struct drm_crtc *crtc = NULL;
> > +	struct drm_device *dev = encoder->dev;
> > +	int ret, i = -1;
> > +
> > +	for_each_crtc(dev, possible_crtc) {
> > +		i++;
> > +		if (!(encoder->possible_crtcs & (1 << i)))
> > +			continue;
> > +
> > +		ret = drm_modeset_lock(&possible_crtc->mutex, ctx);
> > +		if (ret)
> > +			return ERR_PTR(ret);
> > +
> > +		if (possible_crtc->state->enable) {
> > +			drm_modeset_unlock(&possible_crtc->mutex);
> > +			continue;
> > +		}
> > +
> > +		crtc = possible_crtc;
> > +		break;
> 
> This could be replaced with "return possible_crtc;". No need for the extra
> assignment and break.
> 
> I see that in patch 3 you have a debug message for when this returns NULL. It
> would make sense to move that debug here.

Sure, will add it here..

Thanks,
Durga

> 
> Ander
> 
> > +	}
> > +
> > +	return crtc;
> > +}
> > +
> >  bool intel_get_load_detect_pipe(struct drm_connector *connector,
> >  				struct drm_display_mode *mode,
> >  				struct intel_load_detect_pipe *old, @@ -
> 10412,7 +10449,6 @@ bool
> > intel_get_load_detect_pipe(struct drm_connector *connector,
> >  	struct intel_crtc *intel_crtc;
> >  	struct intel_encoder *intel_encoder =
> >  		intel_attached_encoder(connector);
> > -	struct drm_crtc *possible_crtc;
> >  	struct drm_encoder *encoder = &intel_encoder->base;
> >  	struct drm_crtc *crtc = NULL;
> >  	struct drm_device *dev = encoder->dev; @@ -10421,7 +10457,7 @@
> bool
> > intel_get_load_detect_pipe(struct drm_connector *connector,
> >  	struct drm_atomic_state *state = NULL, *restore_state = NULL;
> >  	struct drm_connector_state *connector_state;
> >  	struct intel_crtc_state *crtc_state;
> > -	int ret, i = -1;
> > +	int ret;
> >
> >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s], [ENCODER:%d:%s]\n",
> >  		      connector->base.id, connector->name, @@ -10451,39
> +10487,15
> > @@ retry:
> >  		ret = drm_modeset_lock(&crtc->mutex, ctx);
> >  		if (ret)
> >  			goto fail;
> > -
> > -		/* Make sure the crtc and connector are running */
> > -		goto found;
> > -	}
> > -
> > -	/* Find an unused one (if possible) */
> > -	for_each_crtc(dev, possible_crtc) {
> > -		i++;
> > -		if (!(encoder->possible_crtcs & (1 << i)))
> > -			continue;
> > -
> > -		ret = drm_modeset_lock(&possible_crtc->mutex, ctx);
> > -		if (ret)
> > +	} else {
> > +		crtc = intel_get_unused_crtc(encoder, ctx);
> > +		if (IS_ERR_OR_NULL(crtc)) {
> > +			ret = PTR_ERR_OR_ZERO(crtc);
> > +			DRM_DEBUG_KMS("no pipe available for load-
> detect\n");
> >  			goto fail;
> > -
> > -		if (possible_crtc->state->enable) {
> > -			drm_modeset_unlock(&possible_crtc->mutex);
> > -			continue;
> >  		}
> > -
> > -		crtc = possible_crtc;
> > -		break;
> > -	}
> > -
> > -	/*
> > -	 * If we didn't find an unused CRTC, don't use any.
> > -	 */
> > -	if (!crtc) {
> > -		DRM_DEBUG_KMS("no pipe available for load-detect\n");
> > -		goto fail;
> >  	}
> >
> > -found:
> >  	intel_crtc = to_intel_crtc(crtc);
> >
> >  	ret = drm_modeset_lock(&crtc->primary->mutex, ctx); diff --git
> > a/drivers/gpu/drm/i915/intel_drv.h
> > b/drivers/gpu/drm/i915/intel_drv.h
> > index e13ce22..27b5dcd 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -1159,6 +1159,8 @@ bool intel_get_load_detect_pipe(struct
> > drm_connector *connector,
> >  void intel_release_load_detect_pipe(struct drm_connector *connector,
> >  				    struct intel_load_detect_pipe *old,
> >  				    struct drm_modeset_acquire_ctx *ctx);
> > +struct drm_crtc *intel_get_unused_crtc(struct drm_encoder *encoder,
> > +				struct drm_modeset_acquire_ctx *ctx);
> >  int intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
> >  			       unsigned int rotation);
> >  struct drm_framebuffer *


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