No functional changes.
v2 (Paulo): Rebase.
v3: Accept Daniel's suggestions:
* remove unclear and duplicated explanation.
* remove marketing like doc and replace by a simple one.
* remove bdw_fbc_sw_flush documentation.
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
---
Documentation/DocBook/drm.tmpl | 5 +++++
drivers/gpu/drm/i915/intel_fbc.c | 44 ++++++++++++++++++++++++++++++++--------
2 files changed, 40 insertions(+), 9 deletions(-)
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 85287cb..8b780ab 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -3926,6 +3926,11 @@ int num_ioctls;</synopsis>
!Idrivers/gpu/drm/i915/intel_psr.c
</sect2>
<sect2>
+ <title>Frame Buffer Compression (FBC)</title>
+!Pdrivers/gpu/drm/i915/intel_fbc.c Frame Buffer Compression (FBC)
+!Idrivers/gpu/drm/i915/intel_fbc.c
+ </sect2>
+ <sect2>
<title>DPIO</title>
!Pdrivers/gpu/drm/i915/i915_reg.h DPIO
<table id="dpiox2">
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index f1eeb86..4daceae 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -21,20 +21,26 @@
* DEALINGS IN THE SOFTWARE.
*/
-#include "intel_drv.h"
-#include "i915_drv.h"
-
-/* FBC, or Frame Buffer Compression, is a technique employed to compress the
- * framebuffer contents in-memory, aiming at reducing the required bandwidth
- * during in-memory transfers and, therefore, reduce the power packet.
+/**
+ * DOC: Frame Buffer Compression (FBC)
+ *
+ * FBC tries to save memory bandwidth (and so power consumption) by
+ * compressing the amount of memory used by the display. It is total
+ * transparent to user space and completely handled in the kernel.
*
* The benefits of FBC are mostly visible with solid backgrounds and
- * variation-less patterns.
+ * variation-less patterns. It comes from keeping the memory footprint small
+ * and having fewer memory pages opened and accessed for refreshing the display.
*
- * FBC-related functionality can be enabled by the means of the
- * i915.i915_fbc_enable parameter
+ * i915 is responsible to reserve stolen memory for FBC and configure its
+ * offset on proper registers. The hardware takes care of all
+ * compress/decompress. However there are many known cases where we have to
+ * forcibly disable it to allow proper screen updates.
*/
+#include "intel_drv.h"
+#include "i915_drv.h"
+
static void i8xx_fbc_disable(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
@@ -318,6 +324,14 @@ static void gen7_fbc_enable(struct drm_crtc *crtc)
DRM_DEBUG_KMS("enabled fbc on plane %c\n", plane_name(intel_crtc->plane));
}
+/**
+ * intel_fbc_enabled - Is FBC enabled?
+ * @dev: the drm_device
+ *
+ * This function is used to verify the current state of FBC.
+ * FIXME: This should be tracked in the plane config eventually
+ * instead of queried at runtime for most callers.
+ */
bool intel_fbc_enabled(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
@@ -429,6 +443,12 @@ static void intel_fbc_enable(struct drm_crtc *crtc)
schedule_delayed_work(&work->work, msecs_to_jiffies(50));
}
+/**
+ * intel_fbc_disable - disable FBC
+ * @dev: the drm_device
+ *
+ * This function disables FBC.
+ */
void intel_fbc_disable(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
@@ -643,6 +663,12 @@ out_disable:
i915_gem_stolen_cleanup_compression(dev);
}
+/**
+ * intel_fbc_init - Initialize FBC
+ * @dev_priv: the i915 device
+ *
+ * This function might be called during PM init process.
+ */
void intel_fbc_init(struct drm_i915_private *dev_priv)
{
if (!HAS_FBC(dev_priv)) {
--
1.9.3
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