The coup de grace of the entire journey. No more dropped frames every
10s on my testbox!

I've tried to audit all ->detect and ->get_modes callbacks, but things
became a bit fuzzy after trying to piece together the umpteenth
implemenation. Afaict most drivers just have bog-standard output
register frobbing with a notch of i2c edid reading, nothing which
could potentially race with the newly concurrent pageflip/set_cursor
code. The big exception is load-detection code which requires a
running pipe, but radeon/nouveau seem to to this without touching any
state which can be observed from page_flip (e.g. disabled crtcs
temporarily getting enabled and so a pageflip succeeding).

The only special case I could find is the i915 load detect code. That
uses the normal modeset interface to enable the load-detect crtc, and
so userspace could try to squeeze in a pageflip on the load-detect
pipe. So we need to grab the relevant crtc mutex in there, to avoid
the temporary crtc enabling to sneak out and be visible to userspace.

Note that the sysfs files already stopped grabbing the per-crtc locks,
since I didn't want to bother with doing a interruptible
modeset_lock_all. But since there's very little in-between breakage
(essentially just the ability for userspace to pageflip on load-detect
crtcs when it shouldn't on the i915 driver) I figured I don't need to
bother.
Reviewed-by: NRob Clark <rob@ti.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This is the first step towards introducing the new modeset locking
scheme. The plan is to put helper functions into place at all the
right places step-by-step, so that the final patch to switch on the
new locking scheme doesn't need to touch every single driver.

This helper here will serve as the shotgun solutions for all places
where a more fine-grained locking isn't (yet) implemented.

v2: Fixup kerneldoc for unlock_all.
Reviewed-by: NRob Clark <rob@ti.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

- Add the missing doc for drm_helper_move_panel_connectors_to_head.
- Fixup any outdated stuff in existing sections. I've only looked at
  those kerneldoc headers that actually resulted in a complaint from
  the kerneldoc parser tool.

v2:
- Actually include the docbook snippet in the right patch.
- Fix spelling fail.

v3: It's now called drm_crtc_helper_set_mode, spotted by Laurent
Pinchart.
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

... by properly checking connector->polled. This doesn't matter too
much because the polling work itself gets this slightly more right and
doesn't set repoll if there's nothing to do. But we can do better.

v2: Chris Wilson noticed that I broke polling, since repoll will never
ever be set true. Fix this up, and simplify the logic a bit while at
it.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Otherwise if the detect callback reports a different state than what
the user forced (rather likely), we continously annoy userspace about
a hotplug uevent.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Actually there's a reason this stuff is there, and it's called

commit e58f637b
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Aug 20 09:13:36 2010 +0100

    drm/kms: Add a module parameter to disable polling

The idea has been that users can enable/disable polling at runtime. So
the quick hack has been to just re-enable the output polling if xrandr
asks for the latest state of the connectors.

The problem with that hack is that when we force connectors to another
state than what would be detected, we nicely ping-pong:
- Userspace calls probe, gets the forced state, but polling starts
  again.
- Polling notices that the state is actually different, wakes up
  userspace.
- Repeat.

As that commit already explains, the right fix would be to make the
locking more fine-grained, so that hotplug detection on one output
does not interfere with cursor updates on another crtc.

But that is way too much work. So let's just safe this gross hack by
caching the last-seen state of drm_kms_helper_poll for that driver,
and only fire up the poll engine again if it changed from off to on.

v2: Fixup the edge detection of drm_kms_helper_poll.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49907Tested-by: NTvrtko Ursulin <tvrtko.ursulin@onelan.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

All drivers already have a work item to run the hpd code, so we don't
need to launch a new one in the helper code. Dave Airlie mentioned
that the cancel+re-queue might paper over DP related hpd ping-pongs,
hence why this is split out.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Instead of reusing the polling code for hpd handling, split them up.
This has a few consequences:
- Don't touch HPD capable connectors in the poll loop.
- Only touch HPD capable connectors in drm_helper_hpd_irq_event.
- We could run the HPD handling directly (because all callers already
  use their own work item), but for easier bisect that happens in it's
  own patch.

The ultimate goal is that drivers grow some smarts about which
connectors have received a hotplug event and only call the detect code
of that connector. But that's a second step.

v2: s/hdp/hpd/, noticed by Adam Jackson. I can't type.

v3: Split out the work item removal as requested by Dave Airlie. This
results in a temporary mode_config.hpd_irq_work item to keep things
the same.

v4: In the hpd_irq_event handler don't bail out if other bits than HPD
are set. This is useful where e.g. hpd is unreliably, but mostly
works. Drivers can then set both HPD and POLL flags, and users get the
best of both worlds: Quick hotplug feedback if the hpd works, but
still reliable detection with the polling. The poll loop already works
the same, and doesn't bail if HPD is set.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Useful if drivers want to be slightly more clever about hotplug
handling.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

x and y parameters are offsets, not width/height
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

Userspace seems to like this, see

commit cb0953d7
Author: Adam Jackson <ajax@redhat.com>
Date:   Fri Jul 16 14:46:29 2010 -0400

    drm/i915: Initialize LVDS and eDP outputs before anything else

    This makes them sort to the front in X, which makes them likely to be
    the primary outputs if you haven't specified a preference in your DE,
    which is likely to be what you want.
Signed-off-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NEric Anholt <eric@anholt.net>

Sorting the connector list after the fact is much easier than trying
to be clever with the init sequence.
Acked-by: NDave Airlie <airlied@gmail.com>
Reviewed-by: NAdam Jackson <ajax@redhat.com>
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Convert #include "..." to #include <path/...> in drivers/gpu/.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NDave Airlie <airlied@redhat.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: NDave Jones <davej@redhat.com>

system_nrt[_freezable]_wq are now spurious.  Mark them deprecated and
convert all users to system[_freezable]_wq.

If you're cc'd and wondering what's going on: Now all workqueues are
non-reentrant, so there's no reason to use system_nrt[_freezable]_wq.
Please use system[_freezable]_wq instead.

This patch doesn't make any functional difference.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-By: NLai Jiangshan <laijs@cn.fujitsu.com>

Cc: Jens Axboe <axboe@kernel.dk>
Cc: David Airlie <airlied@linux.ie>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>

Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

There will be a need for this function in drm_crtc.c later. This
avoids making drm_crtc.c depend on drm_crtc_helper.c.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Broken monitors and/or broken graphic boards may send erroneous or no
EDID data. This also applies to broken KVM devices that are unable to
correctly forward the EDID data of the connected monitor but invent
their own fantasy data.

This patch allows to specify an EDID data set to be used instead of
probing the monitor for it. It contains built-in data sets of frequently
used screen resolutions. In addition, a particular EDID data set may be
provided in the /lib/firmware directory and loaded via the firmware
interface. The name is passed to the kernel as module parameter of the
drm_kms_helper module either when loaded
  options drm_kms_helper edid_firmware=edid/1280x1024.bin
or as kernel commandline parameter
  drm_kms_helper.edid_firmware=edid/1280x1024.bin

It is also possible to restrict the usage of a specified EDID data set
to a particular connector. This is done by prepending the name of the
connector to the name of the EDID data set using the syntax
  edid_firmware=[<connector>:]<edid>
such as, for example,
  edid_firmware=DVI-I-1:edid/1920x1080.bin
in which case no other connector will be affected.

The built-in data sets are
Resolution    Name
--------------------------------
1024x768      edid/1024x768.bin
1280x1024     edid/1280x1024.bin
1680x1050     edid/1680x1050.bin
1920x1080     edid/1920x1080.bin

They are ignored, if a file with the same name is available in the
/lib/firmware directory.

The built-in EDID data sets are based on standard timings that may not
apply to a particular monitor and even crash it. Ideally, EDID data of
the connected monitor should be used. They may be obtained through the
drm/cardX/cardX-<connector>/edid entry in the /sys/devices PCI directory
of a correctly working graphics adapter.

It is even possible to specify the name of an EDID data set on-the-fly
via the /sys/module interface, e.g.
echo edid/myedid.bin >/sys/module/drm_kms_helper/parameters/edid_firmware
The new screen mode is considered when the related kernel function is
called for the first time after the change. Such calls are made when the
X server is started or when the display settings dialog is opened in an
already running X server.
Signed-off-by: NCarsten Emde <C.Emde@osadl.org>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Check drm_mode_object_get() return value everywhere.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

list_for_each_entry_safe is for walking a list safe against removal
of entries. Here, no entries are removed, so use list_for_each_entry.
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NDave Airlie <airlied@redhat.com>

This function returns the number of planes used by a specific pixel
format.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NRob Clark <rob.clark@linaro.org>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Call connector->funcs->dpms(DPMS_ON) rather than just setting
connector->dpms = DPMS_ON.  This ensures that if the connector
has something to do to enable the output (rather than just using
drm_helper_connector_dpms helper directly), that this happens
at bootup.  This solves an issue with connectors not getting
enabled from fbcon_init() when the driver is loaded.
Signed-off-by: NRob Clark <rob@ti.com>
Reviewed-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Otherwise each driver would need to keep the information inside
their own framebuffer object structure. Also add offsets[]. BOs
on the other hand are driver specific, so those can be kept in
driver specific structures.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Disabling the CRTC by setting its framebuffer to NULL, as used by
drm_framebuffer_cleanup(), was failing to pass the current framebuffer
to the crtc_func->disable callback. This is because of the dance within
drm_crtc_helper_set_config to pass the new_fb (NULL in this case) to the
drm_crtc_helper_set_mode with the currently attached fb as a parameter.
drm_crtc_helper_set_mode treats this as a no-op and the encoder is still
enabled. And so the current fb is forgotten before the call to
drm_helper_disable_unused_functions.

This patch treats disabling the CRTC as a simple special case rather
than adding further complexity into the configuration logic.

This fixes a pin-leak of the fb bo on Xserver close.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDave Airlie <airlied@redhat.com>

This is used by nearly everyone including vmwgfx which doesn't generally
use the fb helper.
Signed-off-by: NDave Airlie <airlied@redhat.com>

To properly support the various plane formats supported by different
hardware, the kernel must know the pixel format of a framebuffer object.
So add a new ioctl taking a format argument corresponding to a fourcc
name from the new drm_fourcc.h header file.  Implement the fb creation
hooks in terms of the new mode_fb_cmd2 using helpers where the old
bpp/depth values are needed.

v2: create DRM specific fourcc header file for sharing with libdrm etc
v3: fix rebase failure and use DRM fourcc codes in intel_display.c and
    update commit message
v4: make fb_cmd2 handle field into an array for multi-object formats
    pull in Ville's fix for the memcpy in drm_plane_init
    apply Ville's cleanup to zero out fb_cmd2 arg in drm_mode_addfb
v5: add 'flags' field for interlaced support (from Ville)
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: NAlan Cox <alan@lxorguk.ukuu.org.uk>
Reviewed-by: NRob Clark <rob.clark@linaro.org>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDave Airlie <airlied@redhat.com>

We restore the CRTC, encoder, and connector configurations, but if the
mode set failed, the attached display may have been turned off, so we
need to try set_config again to restore things to the way they were.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: NAlex Deucher <alexdeucher@gmail.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

They need this to get all the EXPORT_SYMBOL variants and THIS_MODULE
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

Signed-off-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

To properly drive a framebuffer with a new depth or bpp, dither settings
and link bandwidth calculations may change, so make sure we go through a
full mode set in that case.
Reported-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NKeith Packard <keithp@keithp.com>

In drm_crtc_helper_set_config, instead of always forcing all outputs
to DRM_MODE_DPMS_ON, only set them if the CRTC is actually getting a
mode set, as any mode set will turn all outputs on.

This fixes https://lkml.org/lkml/2011/1/24/457Signed-off-by: NKeith Packard <keithp@keithp.com>
Cc: stable@kernel.org (2.6.37)
Reported-and-tested-by: NCarlos R. Mafra <crmafra2@gmail.com>
Tested-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

By setting the FB of a CRTC to NULL, we are turning off the CRTC (and so
disable the unused encoders and connectors). As such we can simplify the
later tests by making sure the set->mode is NULL. Setting the
num_connectors to zero means that we do not need to loop over the unused
connectors.

All current usage appears correct, this only builds additional defense
into the routine.

References: https://bugzilla.kernel.org/show_bug.cgi?id=27722Tested-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

In drm_crtc_helper_set_config, we call drm_crtc_helper_set_mode which
may return early and do no operation if the crtc is to be disabled. In
this case we merrily swap to the new fb, discarding the old_fb believing
that it has been cleaned up. However, due to the early return, the
old_fb was not presented to the backend for correct reaping, and nor was
the new one - which is about to be reaped via the
drm_helper_disable_unused_functions(), leading to incorrect refcounting
of the pinned objects.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=27722
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=29857
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=29230Tested-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

... or else we may end up disabling the wrong framebuffer, leading to an
OOPS, e.g:

[ 6033.229012] kernel BUG at drivers/gpu/drm/i915/i915_gem.c:3271!
[ 6033.229012] invalid opcode: 0000 [#1] SMP
[ 6033.229012] last sysfs file:
/sys/devices/virtual/backlight/acpi_video0/uevent
[ 6033.229012] Modules linked in: sunrpc cpufreq_ondemand acpi_cpufreq
mperf snd_hda_codec_analog snd_hda_intel snd_hda_codec snd_hwdep snd_seq
snd_seq_device snd_pcm snd_timer thinkpad_acpi ppdev snd r852 sm_common
iTCO_wdt uvcvideo i2c_i801 iTCO_vendor_support microcode wmi nand
videodev nand_ids nand_ecc snd_page_alloc parport_pc parport mtd
soundcore joydev v4l1_compat pcspkr uinput ipv6 sdhci_pci sdhci mmc_core
yenta_socket i915 drm_kms_helper drm i2c_algo_bit i2c_core video output
[last unloaded: scsi_wait_scan]
[ 6033.229012]
[ 6033.229012] Pid: 4834, comm: Xorg Not tainted 2.6.37-rc8+ #25 7661BL5/7661BL5
[ 6033.229012] EIP: 0060:[<f86fda5e>] EFLAGS: 00013246 CPU: 0
[ 6033.229012] EIP is at i915_gem_object_unpin+0x23/0x76 [i915]
[ 6033.229012] EAX: f68a4000 EBX: f6831f00 ECX: 000600fa EDX: f68a8000
[ 6033.229012] ESI: f68a4014 EDI: f68a42b8 EBP: f2169c44 ESP: f2169c3c
[ 6033.229012]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
[ 6033.229012] Process Xorg (pid: 4834, ti=f2168000 task=f21c8000 task.ti=f2168000)
[ 6033.229012] Stack:
[ 6033.229012]  f3a84800 f68a4014 f2169c54 f87045d8 f3a84800 f872d9a8 f2169c68 f7fd8091
[ 6033.229012]  f3b952a4 00000000 f68a414c f2169cf0 f7fd9377 00000000 00000000 f7fd98b0
[ 6033.229012]  f7fd9f4e 0000000f f7f328a0 00000000 00000000 00000000 f2169ca4 f68a414c
[ 6033.229012] Call Trace:
[ 6033.229012]  [<f87045d8>] ? intel_crtc_disable+0x36/0x41 [i915]
[ 6033.229012]  [<f7fd8091>] ?  drm_helper_disable_unused_functions+0xcd/0xf9 [drm_kms_helper]
[ 6033.229012]  [<f7fd9377>] ? drm_crtc_helper_set_config+0x62a/0x7f7 [drm_kms_helper]
[ 6033.229012]  [<c04daa10>] ? __slab_free+0x1b/0xa4
[ 6033.229012]  [<f7fd7e62>] ? drm_fb_helper_initial_config+0x466/0x497 [drm_kms_helper]
[ 6033.229012]  [<f7fd7ea3>] ? drm_fb_helper_restore+0x10/0x2a [drm_kms_helper]
[ 6033.229012]  [<f86f2577>] ? i915_driver_lastclose+0x2a/0x57 [i915]
[ 6033.229012]  [<f7f1989f>] ? drm_lastclose+0x45/0x23e [drm]
[ 6033.229012]  [<f7f1a0b4>] ? drm_release+0x462/0x4d7 [drm]
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

Always useful to know just which connector was polled and had its
status updated.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDave Airlie <airlied@redhat.com>

This reverts commit 541cc966.

Wei Yonjun reported this caused a regression against Intel VGA hotplug
on his G33 hw.
Signed-off-by: NDave Airlie <airlied@redhat.com>

Prevents code that assumes that the encoder is active when asked to be
disabled from dying a horrible death.
Reported-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDave Airlie <airlied@redhat.com>

In order to correctly report monitor connected status changes, the
previous monitor status must be recorded in the connector->status
value instead of being discarded.
Signed-off-by: NKeith Packard <keithp@keithp.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

When setting a new crtc configuration, force the DPMS state of all
connectors to ON. Otherwise, they'll be left at OFF and a future mode set
that disables the specified connector will not turn the connector off.
Signed-off-by: NKeith Packard <keithp@keithp.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

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: NMario Kleiner <mario.kleiner@tuebingen.mpg.de>
Signed-off-by: NDave Airlie <airlied@redhat.com>