drm/i915: DocBook integration for frontbuffer tracking

I shouldn't ask everyone to do this and fail myself ...

This extracts all the frontbuffer tracking functions into
intel_frontbuffer.c, adds a DOC overview section and also adds the
missing kerneldoc for i915_gem_track_fb and also pulls it into the
same section for convenience.

v2: Don't forget about the header files.

v3: Oops, might check compilation next time around. To make my life
easier drop the increase_pllclock from set_base_atomic since really,
it doesn't matter if you see your Oops or kgdb with a tiny bit of lag.

v4: Try to better explain how to actually use this, requested by Paulo
on irc.

v5: Explain invalidate/flush a bit clearer.

v6: s/business/busyness/

Acked-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Vandana Kannan <vandana.kannan@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

1 files changed, 277 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_frontbuffer.c b/drivers/gpu/drm/i915/intel_frontbuffer.c
new file mode 100644
index 000000000000..f74744c091cb
--- /dev/null
+++ b/drivers/gpu/drm/i915/intel_frontbuffer.c
@@ -0,0 +1,277 @@
+/*
+ * Copyright © 2014 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Authors:
+ *      Daniel Vetter <daniel.vetter@ffwll.ch>
+ */
+
+/**
+ * DOC: frontbuffer tracking
+ *
+ * Many features require us to track changes to the currently active
+ * frontbuffer, especially rendering targetted at the frontbuffer.
+ *
+ * To be able to do so GEM tracks frontbuffers using a bitmask for all possible
+ * frontbuffer slots through i915_gem_track_fb(). The function in this file are
+ * then called when the contents of the frontbuffer are invalidated, when
+ * frontbuffer rendering has stopped again to flush out all the changes and when
+ * the frontbuffer is exchanged with a flip. Subsystems interested in
+ * frontbuffer changes (e.g. PSR, FBC, DRRS) should directly put their callbacks
+ * into the relevant places and filter for the frontbuffer slots that they are
+ * interested int.
+ *
+ * On a high level there are two types of powersaving features. The first one
+ * work like a special cache (FBC and PSR) and are interested when they should
+ * stop caching and when to restart caching. This is done by placing callbacks
+ * into the invalidate and the flush functions: At invalidate the caching must
+ * be stopped and at flush time it can be restarted. And maybe they need to know
+ * when the frontbuffer changes (e.g. when the hw doesn't initiate an invalidate
+ * and flush on its own) which can be achieved with placing callbacks into the
+ * flip functions.
+ *
+ * The other type of display power saving feature only cares about busyness
+ * (e.g. DRRS). In that case all three (invalidate, flush and flip) indicate
+ * busyness. There is no direct way to detect idleness. Instead an idle timer
+ * work delayed work should be started from the flush and flip functions and
+ * cancelled as soon as busyness is detected.
+ *
+ * Note that there's also an older frontbuffer activity tracking scheme which
+ * just trackings general activity. This is done by the various mark_busy and
+ * mark_idle functions. For display power management features using these
+ * functions is deprecated and should be avoided.
+ */
+
+#include <drm/drmP.h>
+
+#include "intel_drv.h"
+#include "i915_drv.h"
+
+static void intel_increase_pllclock(struct drm_device *dev,
+                                    enum pipe pipe)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+        int dpll_reg = DPLL(pipe);
+        int dpll;
+
+        if (!HAS_GMCH_DISPLAY(dev))
+                return;
+
+        if (!dev_priv->lvds_downclock_avail)
+                return;
+
+        dpll = I915_READ(dpll_reg);
+        if (!HAS_PIPE_CXSR(dev) && (dpll & DISPLAY_RATE_SELECT_FPA1)) {
+                DRM_DEBUG_DRIVER("upclocking LVDS\n");
+
+                assert_panel_unlocked(dev_priv, pipe);
+
+                dpll &= ~DISPLAY_RATE_SELECT_FPA1;
+                I915_WRITE(dpll_reg, dpll);
+                intel_wait_for_vblank(dev, pipe);
+
+                dpll = I915_READ(dpll_reg);
+                if (dpll & DISPLAY_RATE_SELECT_FPA1)
+                        DRM_DEBUG_DRIVER("failed to upclock LVDS!\n");
+        }
+}
+
+/**
+ * intel_mark_fb_busy - mark given planes as busy
+ * @dev: DRM device
+ * @frontbuffer_bits: bits for the affected planes
+ * @ring: optional ring for asynchronous commands
+ *
+ * This function gets called every time the screen contents change. It can be
+ * used to keep e.g. the update rate at the nominal refresh rate with DRRS.
+ */
+static void intel_mark_fb_busy(struct drm_device *dev,
+                               unsigned frontbuffer_bits,
+                               struct intel_engine_cs *ring)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+        enum pipe pipe;
+
+        if (!i915.powersave)
+                return;
+
+        for_each_pipe(dev_priv, pipe) {
+                if (!(frontbuffer_bits & INTEL_FRONTBUFFER_ALL_MASK(pipe)))
+                        continue;
+
+                intel_increase_pllclock(dev, pipe);
+                if (ring && intel_fbc_enabled(dev))
+                        ring->fbc_dirty = true;
+        }
+}
+
+/**
+ * intel_fb_obj_invalidate - invalidate frontbuffer object
+ * @obj: GEM object to invalidate
+ * @ring: set for asynchronous rendering
+ *
+ * This function gets called every time rendering on the given object starts and
+ * frontbuffer caching (fbc, low refresh rate for DRRS, panel self refresh) must
+ * be invalidated. If @ring is non-NULL any subsequent invalidation will be delayed
+ * until the rendering completes or a flip on this frontbuffer plane is
+ * scheduled.
+ */
+void intel_fb_obj_invalidate(struct drm_i915_gem_object *obj,
+                             struct intel_engine_cs *ring)
+{
+        struct drm_device *dev = obj->base.dev;
+        struct drm_i915_private *dev_priv = dev->dev_private;
+
+        WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+
+        if (!obj->frontbuffer_bits)
+                return;
+
+        if (ring) {
+                mutex_lock(&dev_priv->fb_tracking.lock);
+                dev_priv->fb_tracking.busy_bits
+                        |= obj->frontbuffer_bits;
+                dev_priv->fb_tracking.flip_bits
+                        &= ~obj->frontbuffer_bits;
+                mutex_unlock(&dev_priv->fb_tracking.lock);
+        }
+
+        intel_mark_fb_busy(dev, obj->frontbuffer_bits, ring);
+
+        intel_edp_psr_invalidate(dev, obj->frontbuffer_bits);
+}
+
+/**
+ * intel_frontbuffer_flush - flush frontbuffer
+ * @dev: DRM device
+ * @frontbuffer_bits: frontbuffer plane tracking bits
+ *
+ * This function gets called every time rendering on the given planes has
+ * completed and frontbuffer caching can be started again. Flushes will get
+ * delayed if they're blocked by some oustanding asynchronous rendering.
+ *
+ * Can be called without any locks held.
+ */
+void intel_frontbuffer_flush(struct drm_device *dev,
+                             unsigned frontbuffer_bits)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+
+        /* Delay flushing when rings are still busy.*/
+        mutex_lock(&dev_priv->fb_tracking.lock);
+        frontbuffer_bits &= ~dev_priv->fb_tracking.busy_bits;
+        mutex_unlock(&dev_priv->fb_tracking.lock);
+
+        intel_mark_fb_busy(dev, frontbuffer_bits, NULL);
+
+        intel_edp_psr_flush(dev, frontbuffer_bits);
+
+        /*
+         * FIXME: Unconditional fbc flushing here is a rather gross hack and
+         * needs to be reworked into a proper frontbuffer tracking scheme like
+         * psr employs.
+         */
+        if (IS_BROADWELL(dev))
+                gen8_fbc_sw_flush(dev, FBC_REND_CACHE_CLEAN);
+}
+
+/**
+ * intel_fb_obj_flush - flush frontbuffer object
+ * @obj: GEM object to flush
+ * @retire: set when retiring asynchronous rendering
+ *
+ * This function gets called every time rendering on the given object has
+ * completed and frontbuffer caching can be started again. If @retire is true
+ * then any delayed flushes will be unblocked.
+ */
+void intel_fb_obj_flush(struct drm_i915_gem_object *obj,
+                        bool retire)
+{
+        struct drm_device *dev = obj->base.dev;
+        struct drm_i915_private *dev_priv = dev->dev_private;
+        unsigned frontbuffer_bits;
+
+        WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+
+        if (!obj->frontbuffer_bits)
+                return;
+
+        frontbuffer_bits = obj->frontbuffer_bits;
+
+        if (retire) {
+                mutex_lock(&dev_priv->fb_tracking.lock);
+                /* Filter out new bits since rendering started. */
+                frontbuffer_bits &= dev_priv->fb_tracking.busy_bits;
+
+                dev_priv->fb_tracking.busy_bits &= ~frontbuffer_bits;
+                mutex_unlock(&dev_priv->fb_tracking.lock);
+        }
+
+        intel_frontbuffer_flush(dev, frontbuffer_bits);
+}
+
+/**
+ * intel_frontbuffer_flip_prepare - prepare asnychronous frontbuffer flip
+ * @dev: DRM device
+ * @frontbuffer_bits: frontbuffer plane tracking bits
+ *
+ * This function gets called after scheduling a flip on @obj. The actual
+ * frontbuffer flushing will be delayed until completion is signalled with
+ * intel_frontbuffer_flip_complete. If an invalidate happens in between this
+ * flush will be cancelled.
+ *
+ * Can be called without any locks held.
+ */
+void intel_frontbuffer_flip_prepare(struct drm_device *dev,
+                                    unsigned frontbuffer_bits)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+
+        mutex_lock(&dev_priv->fb_tracking.lock);
+        dev_priv->fb_tracking.flip_bits
+                |= frontbuffer_bits;
+        mutex_unlock(&dev_priv->fb_tracking.lock);
+}
+
+/**
+ * intel_frontbuffer_flip_complete - complete asynchronous frontbuffer flush
+ * @dev: DRM device
+ * @frontbuffer_bits: frontbuffer plane tracking bits
+ *
+ * This function gets called after the flip has been latched and will complete
+ * on the next vblank. It will execute the fush if it hasn't been cancalled yet.
+ *
+ * Can be called without any locks held.
+ */
+void intel_frontbuffer_flip_complete(struct drm_device *dev,
+                                     unsigned frontbuffer_bits)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+
+        mutex_lock(&dev_priv->fb_tracking.lock);
+        /* Mask any cancelled flips. */
+        frontbuffer_bits &= dev_priv->fb_tracking.flip_bits;
+        dev_priv->fb_tracking.flip_bits &= ~frontbuffer_bits;
+        mutex_unlock(&dev_priv->fb_tracking.lock);
+
+        intel_frontbuffer_flush(dev, frontbuffer_bits);
+}
+