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authorMario Kleiner <mario.kleiner@tuebingen.mpg.de>2010-10-23 04:20:23 +0200
committerDave Airlie <airlied@redhat.com>2010-11-22 02:45:05 +0100
commit27641c3f003e7f3b6585c01d8a788883603eb262 (patch)
treee26eb639c4b5f429d30033d598544f82479d1ea3 /include
parentLinux 2.6.37-rc3 (diff)
downloadlinux-27641c3f003e7f3b6585c01d8a788883603eb262.tar.xz
linux-27641c3f003e7f3b6585c01d8a788883603eb262.zip
drm/vblank: Add support for precise vblank timestamping.
The DRI2 swap & sync implementation needs precise vblank counts and precise timestamps corresponding to those vblank counts. For conformance to the OpenML OML_sync_control extension specification the DRM timestamp associated with a vblank count should correspond to the start of video scanout of the first scanline of the video frame following the vblank interval for that vblank count. Therefore we need to carry around precise timestamps for vblanks. Currently the DRM and KMS drivers generate timestamps ad-hoc via do_gettimeofday() in some places. The resulting timestamps are sometimes not very precise due to interrupt handling delays, they don't conform to OML_sync_control and some are wrong, as they aren't taken synchronized to the vblank. This patch implements support inside the drm core for precise and robust timestamping. It consists of the following interrelated pieces. 1. Vblank timestamp caching: A per-crtc ringbuffer stores the most recent vblank timestamps corresponding to vblank counts. The ringbuffer can be read out lock-free via the accessor function: struct timeval timestamp; vblankcount = drm_vblank_count_and_time(dev, crtcid, &timestamp). The function returns the current vblank count and the corresponding timestamp for start of video scanout following the vblank interval. It can be used anywhere between enclosing drm_vblank_get(dev, crtcid) and drm_vblank_put(dev,crtcid) statements. It is used inside the drmWaitVblank ioctl and in the vblank event queueing and handling. It should be used by kms drivers for timestamping of bufferswap completion. The timestamp ringbuffer is reinitialized each time vblank irq's get reenabled in drm_vblank_get()/ drm_update_vblank_count(). It is invalidated when vblank irq's get disabled. The ringbuffer is updated inside drm_handle_vblank() at each vblank irq. 2. Calculation of precise vblank timestamps: drm_get_last_vbltimestamp() is used to compute the timestamp for the end of the most recent vblank (if inside active scanout), or the expected end of the current vblank interval (if called inside a vblank interval). The function calls into a new optional kms driver entry point dev->driver->get_vblank_timestamp() which is supposed to provide the precise timestamp. If a kms driver doesn't implement the entry point or if the call fails, a simple do_gettimeofday() timestamp is returned as crude approximation of the true vblank time. A new drm module parameter drm.timestamp_precision_usec allows to disable high precision timestamps (if set to zero) or to specify the maximum acceptable error in the timestamps in microseconds. Kms drivers could implement their get_vblank_timestamp() function in a gpu specific way, as long as returned timestamps conform to OML_sync_control, e.g., by use of gpu specific hardware timestamps. Optionally, kms drivers can simply wrap and use the new utility function drm_calc_vbltimestamp_from_scanoutpos(). This function calls a new optional kms driver function dev->driver->get_scanout_position() which returns the current horizontal and vertical video scanout position of the crtc. The scanout position together with the drm_display_timing of the current video mode is used to calculate elapsed time relative to start of active scanout for the current video frame. This elapsed time is subtracted from the current do_gettimeofday() time to get the timestamp corresponding to start of video scanout. Currently non-interlaced, non-doublescan video modes, with or without panel scaling are handled correctly. Interlaced/ doublescan modes are tbd in a future patch. 3. Filtering of redundant vblank irq's and removal of some race-conditions in the vblank irq enable/disable path: Some gpu's (e.g., Radeon R500/R600) send spurious vblank irq's outside the vblank if vblank irq's get reenabled. These get detected by use of the vblank timestamps and filtered out to avoid miscounting of vblanks. Some race-conditions between the vblank irq enable/disable functions, the vblank irq handler and the gpu itself (updating its hardware vblank counter in the "wrong" moment) are fixed inside vblank_disable_and_save() and drm_update_vblank_count() by use of the vblank timestamps and a new spinlock dev->vblank_time_lock. The time until vblank irq disable is now configurable via a new drm module parameter drm.vblankoffdelay to allow experimentation with timeouts that are much shorter than the current 5 seconds and should allow longer vblank off periods for better power savings. Followup patches will use these new functions to implement precise timestamping for the intel and radeon kms drivers. Signed-off-by: Mario Kleiner <mario.kleiner@tuebingen.mpg.de> Signed-off-by: Dave Airlie <airlied@redhat.com>
Diffstat (limited to 'include')
-rw-r--r--include/drm/drmP.h93
-rw-r--r--include/drm/drm_crtc.h9
2 files changed, 102 insertions, 0 deletions
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 274eaaa15c36..2b3398004aa5 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -683,6 +683,21 @@ struct drm_master {
void *driver_priv; /**< Private structure for driver to use */
};
+/* Size of ringbuffer for vblank timestamps. Just double-buffer
+ * in initial implementation.
+ */
+#define DRM_VBLANKTIME_RBSIZE 2
+
+/* Flags and return codes for get_vblank_timestamp() driver function. */
+#define DRM_CALLED_FROM_VBLIRQ 1
+#define DRM_VBLANKTIME_SCANOUTPOS_METHOD (1 << 0)
+#define DRM_VBLANKTIME_INVBL (1 << 1)
+
+/* get_scanout_position() return flags */
+#define DRM_SCANOUTPOS_VALID (1 << 0)
+#define DRM_SCANOUTPOS_INVBL (1 << 1)
+#define DRM_SCANOUTPOS_ACCURATE (1 << 2)
+
/**
* DRM driver structure. This structure represent the common code for
* a family of cards. There will one drm_device for each card present
@@ -760,6 +775,68 @@ struct drm_driver {
*/
int (*device_is_agp) (struct drm_device *dev);
+ /**
+ * Called by vblank timestamping code.
+ *
+ * Return the current display scanout position from a crtc.
+ *
+ * \param dev DRM device.
+ * \param crtc Id of the crtc to query.
+ * \param *vpos Target location for current vertical scanout position.
+ * \param *hpos Target location for current horizontal scanout position.
+ *
+ * Returns vpos as a positive number while in active scanout area.
+ * Returns vpos as a negative number inside vblank, counting the number
+ * of scanlines to go until end of vblank, e.g., -1 means "one scanline
+ * until start of active scanout / end of vblank."
+ *
+ * \return Flags, or'ed together as follows:
+ *
+ * DRM_SCANOUTPOS_VALID = Query successfull.
+ * DRM_SCANOUTPOS_INVBL = Inside vblank.
+ * DRM_SCANOUTPOS_ACCURATE = Returned position is accurate. A lack of
+ * this flag means that returned position may be offset by a constant
+ * but unknown small number of scanlines wrt. real scanout position.
+ *
+ */
+ int (*get_scanout_position) (struct drm_device *dev, int crtc,
+ int *vpos, int *hpos);
+
+ /**
+ * Called by \c drm_get_last_vbltimestamp. Should return a precise
+ * timestamp when the most recent VBLANK interval ended or will end.
+ *
+ * Specifically, the timestamp in @vblank_time should correspond as
+ * closely as possible to the time when the first video scanline of
+ * the video frame after the end of VBLANK will start scanning out,
+ * the time immmediately after end of the VBLANK interval. If the
+ * @crtc is currently inside VBLANK, this will be a time in the future.
+ * If the @crtc is currently scanning out a frame, this will be the
+ * past start time of the current scanout. This is meant to adhere
+ * to the OpenML OML_sync_control extension specification.
+ *
+ * \param dev dev DRM device handle.
+ * \param crtc crtc for which timestamp should be returned.
+ * \param *max_error Maximum allowable timestamp error in nanoseconds.
+ * Implementation should strive to provide timestamp
+ * with an error of at most *max_error nanoseconds.
+ * Returns true upper bound on error for timestamp.
+ * \param *vblank_time Target location for returned vblank timestamp.
+ * \param flags 0 = Defaults, no special treatment needed.
+ * \param DRM_CALLED_FROM_VBLIRQ = Function is called from vblank
+ * irq handler. Some drivers need to apply some workarounds
+ * for gpu-specific vblank irq quirks if flag is set.
+ *
+ * \returns
+ * Zero if timestamping isn't supported in current display mode or a
+ * negative number on failure. A positive status code on success,
+ * which describes how the vblank_time timestamp was computed.
+ */
+ int (*get_vblank_timestamp) (struct drm_device *dev, int crtc,
+ int *max_error,
+ struct timeval *vblank_time,
+ unsigned flags);
+
/* these have to be filled in */
irqreturn_t(*irq_handler) (DRM_IRQ_ARGS);
@@ -983,6 +1060,8 @@ struct drm_device {
wait_queue_head_t *vbl_queue; /**< VBLANK wait queue */
atomic_t *_vblank_count; /**< number of VBLANK interrupts (driver must alloc the right number of counters) */
+ struct timeval *_vblank_time; /**< timestamp of current vblank_count (drivers must alloc right number of fields) */
+ spinlock_t vblank_time_lock; /**< Protects vblank count and time updates during vblank enable/disable */
spinlock_t vbl_lock;
atomic_t *vblank_refcount; /* number of users of vblank interruptsper crtc */
u32 *last_vblank; /* protected by dev->vbl_lock, used */
@@ -1284,11 +1363,22 @@ extern int drm_wait_vblank(struct drm_device *dev, void *data,
struct drm_file *filp);
extern int drm_vblank_wait(struct drm_device *dev, unsigned int *vbl_seq);
extern u32 drm_vblank_count(struct drm_device *dev, int crtc);
+extern u32 drm_vblank_count_and_time(struct drm_device *dev, int crtc,
+ struct timeval *vblanktime);
extern void drm_handle_vblank(struct drm_device *dev, int crtc);
extern int drm_vblank_get(struct drm_device *dev, int crtc);
extern void drm_vblank_put(struct drm_device *dev, int crtc);
extern void drm_vblank_off(struct drm_device *dev, int crtc);
extern void drm_vblank_cleanup(struct drm_device *dev);
+extern u32 drm_get_last_vbltimestamp(struct drm_device *dev, int crtc,
+ struct timeval *tvblank, unsigned flags);
+extern int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
+ int crtc, int *max_error,
+ struct timeval *vblank_time,
+ unsigned flags,
+ struct drm_crtc *refcrtc);
+extern void drm_calc_timestamping_constants(struct drm_crtc *crtc);
+
/* Modesetting support */
extern void drm_vblank_pre_modeset(struct drm_device *dev, int crtc);
extern void drm_vblank_post_modeset(struct drm_device *dev, int crtc);
@@ -1340,6 +1430,9 @@ extern void drm_put_dev(struct drm_device *dev);
extern int drm_put_minor(struct drm_minor **minor);
extern unsigned int drm_debug;
+extern unsigned int drm_vblank_offdelay;
+extern unsigned int drm_timestamp_precision;
+
extern struct class *drm_class;
extern struct proc_dir_entry *drm_proc_root;
extern struct dentry *drm_debugfs_root;
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 029aa688e787..acd7fade160d 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -351,8 +351,14 @@ struct drm_crtc {
bool enabled;
+ /* Requested mode from modesetting. */
struct drm_display_mode mode;
+ /* Programmed mode in hw, after adjustments for encoders,
+ * crtc, panel scaling etc. Needed for timestamping etc.
+ */
+ struct drm_display_mode hwmode;
+
int x, y;
const struct drm_crtc_funcs *funcs;
@@ -360,6 +366,9 @@ struct drm_crtc {
uint32_t gamma_size;
uint16_t *gamma_store;
+ /* Constants needed for precise vblank and swap timestamping. */
+ s64 framedur_ns, linedur_ns, pixeldur_ns;
+
/* if you are using the helper */
void *helper_private;
};