Commit 6e8acb66 authored by Ville Syrjälä's avatar Ville Syrjälä
Browse files

drm/i915: Add belts and suspenders locking for seamless M/N changes 



Add some (probably overkill) locking to protect the vblank
timestamping constants updates during seamless M/N fastsets.

As everything should be naturally aligned I think the individual
pieces should probably end up updating atomically enough. So this
is only really meant to guarantee everyone sees a consistent whole.

All the drm_vblank.c usage is covered by vblank_time_lock,
and uncore.lock will take care of __intel_get_crtc_scanline()
that can also be called from outside the core vblank functionality.

Currently only crtc_clock and framedur_ns can change, but in
the future might fastset also across eg. vtotal/vblank_end
changes, so let's just grab the locks across the whole thing.

Reviewed-by: default avatarJani Nikula <jani.nikula@intel.com>
Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230310235828.17439-2-ville.syrjala@linux.intel.com
parent 8cb1f95c

drivers/gpu/drm/i915/display/intel_display.c

+23 −1
Original line number Diff line number Diff line
@@ -5907,6 +5907,8 @@ void intel_crtc_update_active_timings(const struct intel_crtc_state *crtc_state) 
	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);

	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);

	struct drm_display_mode adjusted_mode;

	int vmax_vblank_start = 0;

	unsigned long irqflags;



	drm_mode_init(&adjusted_mode, &crtc_state->hw.adjusted_mode);
@@ -5914,11 +5916,28 @@ void intel_crtc_update_active_timings(const struct intel_crtc_state *crtc_state) 
		adjusted_mode.crtc_vtotal = crtc_state->vrr.vmax;

		adjusted_mode.crtc_vblank_end = crtc_state->vrr.vmax;

		adjusted_mode.crtc_vblank_start = intel_vrr_vmin_vblank_start(crtc_state);

		crtc->vmax_vblank_start = intel_vrr_vmax_vblank_start(crtc_state);

		vmax_vblank_start = intel_vrr_vmax_vblank_start(crtc_state);

	}



	/*

	 * Belts and suspenders locking to guarantee everyone sees 100%

	 * consistent state during fastset seamless refresh rate changes.

	 *

	 * vblank_time_lock takes care of all drm_vblank.c stuff, and

	 * uncore.lock takes care of __intel_get_crtc_scanline() which

	 * may get called elsewhere as well.

	 *

	 * TODO maybe just protect everything (including

	 * __intel_get_crtc_scanline()) with vblank_time_lock?

	 * Need to audit everything to make sure it's safe.

	 */

	spin_lock_irqsave(&dev_priv->drm.vblank_time_lock, irqflags);

	spin_lock(&dev_priv->uncore.lock);



	drm_calc_timestamping_constants(&crtc->base, &adjusted_mode);



	crtc->vmax_vblank_start = vmax_vblank_start;



	crtc->mode_flags = crtc_state->mode_flags;



	/*
@@ -5962,6 +5981,9 @@ void intel_crtc_update_active_timings(const struct intel_crtc_state *crtc_state) 
	} else {

		crtc->scanline_offset = 1;

	}



	spin_unlock(&dev_priv->uncore.lock);

	spin_unlock_irqrestore(&dev_priv->drm.vblank_time_lock, irqflags);

}



/*