Re: [PATCH 02/11] drm/i915: Do not acquire crtc state to check clock during modeset.

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Oct 22, 2015 at 01:56:27PM +0200, Maarten Lankhorst wrote:
> Parallel modesets are still not allowed, but this will allow updating
> a different crtc during a modeset if the clock is not changed.
> 
> Additionally when all pipes are DPMS off the cdclk will be lowered
> to the minimum allowed.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 90 ++++++++++++++++++++++--------------
>  drivers/gpu/drm/i915/intel_drv.h     |  9 ++++
>  2 files changed, 64 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 022e628b8520..051a1e2b1c55 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -5237,6 +5237,7 @@ static void modeset_put_power_domains(struct drm_i915_private *dev_priv,
>  
>  static void modeset_update_crtc_power_domains(struct drm_atomic_state *state)
>  {
> +	struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
>  	struct drm_device *dev = state->dev;
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	unsigned long put_domains[I915_MAX_PIPES] = {};
> @@ -5245,13 +5246,20 @@ static void modeset_update_crtc_power_domains(struct drm_atomic_state *state)
>  	int i;
>  
>  	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> -		if (needs_modeset(crtc->state))
> -			put_domains[to_intel_crtc(crtc)->pipe] =
> -				modeset_get_crtc_power_domains(crtc);
> +		struct intel_crtc *intel_crtc =
> +			to_intel_crtc(crtc);
> +		enum pipe pipe = intel_crtc->pipe;
> +
> +		if (!needs_modeset(crtc->state))
> +			continue;
> +
> +		intel_crtc->min_cdclk = intel_state->pipe_cdclk[pipe];
> +
> +		put_domains[pipe] = modeset_get_crtc_power_domains(crtc);
>  	}
>  
>  	if (dev_priv->display.modeset_commit_cdclk) {
> -		unsigned int cdclk = to_intel_atomic_state(state)->cdclk;
> +		unsigned int cdclk = intel_state->cdclk;
>  
>  		if (cdclk != dev_priv->cdclk_freq &&
>  		    !WARN_ON(!state->allow_modeset))
> @@ -5919,7 +5927,6 @@ static int broxton_calc_cdclk(struct drm_i915_private *dev_priv,
>  	/*
>  	 * FIXME:
>  	 * - remove the guardband, it's not needed on BXT
> -	 * - set 19.2MHz bypass frequency if there are no active pipes
>  	 */
>  	if (max_pixclk > 576000*9/10)
>  		return 624000;
> @@ -5929,8 +5936,10 @@ static int broxton_calc_cdclk(struct drm_i915_private *dev_priv,
>  		return 384000;
>  	else if (max_pixclk > 144000*9/10)
>  		return 288000;
> -	else
> +	else if (max_pixclk)
>  		return 144000;
> +	else
> +		return 19200;
>  }
>  
>  /* Compute the max pixel clock for new configuration. Uses atomic state if
> @@ -5939,22 +5948,31 @@ static int intel_mode_max_pixclk(struct drm_device *dev,
>  				 struct drm_atomic_state *state)
>  {
>  	struct intel_crtc *intel_crtc;
> -	struct intel_crtc_state *crtc_state;
> -	int max_pixclk = 0;
> +	int max_pixel_rate = 0;
> +	bool any_active = false;
>  
> -	for_each_intel_crtc(dev, intel_crtc) {
> -		crtc_state = intel_atomic_get_crtc_state(state, intel_crtc);
> -		if (IS_ERR(crtc_state))
> -			return PTR_ERR(crtc_state);
> +	for_each_intel_crtc(state->dev, intel_crtc) {
> +		struct drm_crtc_state *drm_crtc_state;
> +		struct drm_crtc *crtc = &intel_crtc->base;
> +		int pixclk = 0;
>  
> -		if (!crtc_state->base.enable)
> -			continue;
> +		drm_crtc_state = drm_atomic_get_existing_crtc_state(state, crtc);
> +		if (!drm_crtc_state) {
> +			any_active |= intel_crtc->active;
> +			pixclk = intel_crtc->min_cdclk;
> +		} else if (drm_crtc_state->enable) {
> +			struct intel_crtc_state *crtc_state =
> +				to_intel_crtc_state(drm_crtc_state);
> +
> +			any_active |= drm_crtc_state->active;
> +			pixclk = crtc_state->base.adjusted_mode.crtc_clock;
> +		}
>  
> -		max_pixclk = max(max_pixclk,
> -				 crtc_state->base.adjusted_mode.crtc_clock);
> +		to_intel_atomic_state(state)->pipe_cdclk[intel_crtc->pipe] = pixclk;
> +		max_pixel_rate = max(max_pixel_rate, pixclk);
>  	}
>  
> -	return max_pixclk;
> +	return any_active ? max_pixel_rate : 0;
>  }
>  
>  static int valleyview_modeset_calc_cdclk(struct drm_atomic_state *state)
> @@ -9491,29 +9509,35 @@ static void broxton_modeset_commit_cdclk(struct drm_atomic_state *old_state)
>  static int ilk_max_pixel_rate(struct drm_atomic_state *state)
>  {
>  	struct intel_crtc *intel_crtc;
> -	struct intel_crtc_state *crtc_state;
>  	int max_pixel_rate = 0;
> +	bool any_active = false;
>  
>  	for_each_intel_crtc(state->dev, intel_crtc) {
> -		int pixel_rate;
> -
> -		crtc_state = intel_atomic_get_crtc_state(state, intel_crtc);
> -		if (IS_ERR(crtc_state))
> -			return PTR_ERR(crtc_state);
> +		struct drm_crtc_state *drm_crtc_state;
> +		struct drm_crtc *crtc = &intel_crtc->base;
> +		int pixel_rate = 0;
>  
> -		if (!crtc_state->base.enable)
> -			continue;
> +		drm_crtc_state = drm_atomic_get_existing_crtc_state(state, crtc);
> +		if (!drm_crtc_state) {
> +			any_active |= intel_crtc->active;
> +			pixel_rate = intel_crtc->min_cdclk;
> +		} else if (drm_crtc_state->enable) {
> +			struct intel_crtc_state *crtc_state =
> +				to_intel_crtc_state(drm_crtc_state);
>  
> -		pixel_rate = ilk_pipe_pixel_rate(crtc_state);
> +			any_active |= drm_crtc_state->active;
> +			pixel_rate = ilk_pipe_pixel_rate(crtc_state);
>  
> -		/* pixel rate mustn't exceed 95% of cdclk with IPS on BDW */
> -		if (IS_BROADWELL(state->dev) && crtc_state->ips_enabled)
> -			pixel_rate = DIV_ROUND_UP(pixel_rate * 100, 95);
> +			/* pixel rate mustn't exceed 95% of cdclk with IPS on BDW */
> +			if (IS_BROADWELL(state->dev) && crtc_state->ips_enabled)
> +				pixel_rate = DIV_ROUND_UP(pixel_rate * 100, 95);
> +		}
>  
> +		to_intel_atomic_state(state)->pipe_cdclk[intel_crtc->pipe] = pixel_rate;
>  		max_pixel_rate = max(max_pixel_rate, pixel_rate);
>  	}
>  
> -	return max_pixel_rate;
> +	return any_active ? max_pixel_rate : 0;
>  }
>  
>  static void broadwell_set_cdclk(struct drm_device *dev, int cdclk)
> @@ -9612,14 +9636,10 @@ static int broadwell_modeset_calc_cdclk(struct drm_atomic_state *state)
>  	else
>  		cdclk = 337500;
>  
> -	/*
> -	 * FIXME move the cdclk caclulation to
> -	 * compute_config() so we can fail gracegully.
> -	 */
>  	if (cdclk > dev_priv->max_cdclk_freq) {
>  		DRM_ERROR("requested cdclk (%d kHz) exceeds max (%d kHz)\n",
>  			  cdclk, dev_priv->max_cdclk_freq);
> -		cdclk = dev_priv->max_cdclk_freq;
> +		return -EINVAL;
>  	}
>  
>  	to_intel_atomic_state(state)->cdclk = cdclk;
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 51722e657b91..54a2c0da2ece 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -250,6 +250,7 @@ struct intel_atomic_state {
>  	unsigned int cdclk;
>  	bool dpll_set;
>  	struct intel_shared_dpll_config shared_dpll[I915_NUM_PLLS];
> +	unsigned int pipe_cdclk[I915_MAX_PIPES];
>  };
>  
>  struct intel_plane_state {
> @@ -536,8 +537,16 @@ struct intel_crtc {
>  	 * Whether the crtc and the connected output pipeline is active. Implies
>  	 * that crtc->enabled is set, i.e. the current mode configuration has
>  	 * some outputs connected to this crtc.
> +	 *
> +	 * Protected by crtc.mutex and connection_mutex

This needs to be clarified to mean: read-protected by connection_mutex,
writers additionally must hold crtc->mutex. Same below.

Thinking about this a bit more the usual design we do is put the state
copies not into the parent object with funky rules, but instead into the
state of the higher-level objects. So for example the read-only
plane_active state is in crtc_state->plane_mask.

Similarly in this case here I think it would be cleaner design to have a
min_cdclk array in intel_state, setting it to 0 if the pipe is totally
off. That way locking rules are 100% clear: If you need to change it, you
need to copy the global state and acquire connection_mutex. That
automatically gives you read-access to all crtc's min_cdclk.

That way we don't play tricks with get_existing_state, don't add more
depencies on the legacy-encumbered intel_crtc->active and it's just
generally more awesome.

Thoughts?
-Daniel

>  	 */
>  	bool active;
> +
> +	/* Minimum cdclk required for this pipe,
> +	 * protected by crtc.mutex and connection_mutex.
> +	 */
> +	unsigned int min_cdclk;
> +
>  	unsigned long enabled_power_domains;
>  	bool lowfreq_avail;
>  	struct intel_overlay *overlay;
> -- 
> 2.1.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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