Add some additional information (input vs. output port, sink associated
with VC, peer device type, max number of VCs supported) and ensure that
any embedded '\0' characters in a branch device's devid string are not
written to debugfs.

v2: Rebase + change drm_edid_get_monitor_name() call to reflect new
    signature.

v3: Minor changes suggested by Jani + rebase.

v4: Rebase

cc: dri-devel@lists.freedesktop.org
cc: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NJim Bride <jim.bride@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1460654317-31288-2-git-send-email-jim.bride@linux.intel.com

This reverts commit cfcfa086.

This causes the tiling properties to break in some unexpected ways,

Revert it for now.

Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

This is needed to properly deallocate port payload
after downstream branch get unplugged.

In order to do this unplugged MST topology should
be preserved, to find first alive port on path to
unplugged MST topology, and send payload deallocation
request to branch device of found port.

For this mstb and port kref's are used in reversed
order to track when port and branch memory could be
freed.

Added additional functions to find appropriate mstb
as described above.
Signed-off-by: NMykola Lysenko <Mykola.Lysenko@amd.com>
Reviewed-by: NHarry Wentland <Harry.Wentland@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

On DELL U3014 if you clear the table before enabling MST it sometimes
hangs the receiver.
Signed-off-by: NAndrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Reviewed-by: NHarry Wentland <harry.wentland@amd.com>
Cc: stable@vger.kernel.org
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Previous implementation does not handle case below: boot up one MST branch
to DP connector of ASIC. After boot up, hot plug 2nd MST branch to DP output
of 1st MST, GUID is not created for 2nd MST branch. When downstream port of
2nd MST branch send upstream request, it fails because 2nd MST branch GUID
is not available.

New Implementation: only create GUID for MST branch and save it within Branch.
Signed-off-by: NHersen Wu <hersenxs.wu@amd.com>
Reviewed-by: NHarry Wentland <harry.wentland@amd.com>
Cc: stable@vger.kernel.org
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

1. Get edid for all connected MST displays, not only on logical ports,
   in the same thread as MST topology detection is done:
     There are displays that have branches inside w/o logical ports.
     So in case another SST display connected downstream system can
     end-up in situation when 3 DOWN requests sent: two for
    ‘remote i2c read’ and one for ‘enum path resources’, making slots full.

2. Call notification callback in one place in the end of topology discovery/update:
     This is done to reduce number of events sent to userspace in case complex
     topology discovery is going, adding multiple number of connectors;

3. Remove notification callback call from short pulse interrupt processing function:
     This is done in order not to block interrupt processing function, in case any
     MST request will be made from it. Notification will be send from topology
     discovery/update work item.
Signed-off-by: NMykola Lysenko <Mykola.Lysenko@amd.com>
Reviewed-by: NHarry Wentland <Harry.Wentland@amd.com>
Cc: stable@vger.kernel.org
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Our PBN value overflows the 20 bits integer part of the 20.12
fixed point. We need to use 31.32 fixed point to avoid this.

This happens with display clocks larger than 293122 (at 24 bpp),
which we see with the Sharp (and similar) 4k tiled displays.
Signed-off-by: NHarry Wentland <harry.wentland@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

max_payload is limited by the space we have in
drm_dp_mst_topology_mgr::vcpi_mask,payload_mask. We need to track
max_payloads+1 IDs in these masks, see drm_dp_mst_assign_payload_id().
Add a sanity check for this.

Caught by coverity.
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NDavid Weinehall <david.weinehall@intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Otherwise this call would have no effect.

Caught by Coverity.
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NDavid Weinehall <david.weinehall@intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

In drm_dp_mst_allocate_vcpi, it returns true in two paths,
but in one path, there is no reference couting decrease.
Signed-off-by: NInsu Yun <wuninsu@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

This is needed to receive correct port
number from RAD, so MSTB could be found
Acked-by: NDave Airlie <airlied@gmail.com>
Signed-off-by: NMykola Lysenko <Mykola.Lysenko@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

This fix is needed to support more then two
branch displays, so RAD address consist at
least of 2 elements
Acked-by: NDave Airlie <airlied@gmail.com>
Signed-off-by: NMykola Lysenko <Mykola.Lysenko@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

We should always send reply for UP request in order
to make downstream device clean-up resources appropriately.

Issue was that reply for UP request was sent only once.
Acked-by: NDave Airlie <airlied@gmail.com>
Signed-off-by: NMykola Lysenko <Mykola.Lysenko@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

In case broadcast message received in UP request,
RAD cannot be used to identify message originator.
Message should be parsed, originator should be found
by GUID from parsed message.

Also reply with broadcast in case broadcast message
received (for now it is always broadcast)
Acked-by: NDave Airlie <airlied@gmail.com>
Signed-off-by: NMykola Lysenko <Mykola.Lysenko@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

This makes it possibly for drivers to find the associated
mst_port by looking at the payload allocation table.
Signed-off-by: NHarry Wentland <harry.wentland@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449514552-10236-3-git-send-email-harry.wentland@amd.comSigned-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Currently we reply with NACK to UP requests which might
confuse receivers. We haven't seen any actual issues with
this but should still respond to UP requests correctly.
Signed-off-by: NMykola Lysenko <Mykola.Lysenko@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449514552-10236-2-git-send-email-harry.wentland@amd.comSigned-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This adds code to initialise the SDP streams
for a sink in the simplest ordering.

I've no idea how you'd want to control the
ordering at this level, so don't bother
until someone comes up with a use case.
Reviewed-by: NAnder Conselvan de Oliveira <conselvan2@gmail.com>
Signed-off-by: NLibin Yang <libin.yang@linux.intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1449036584-105393-1-git-send-email-libin.yang@linux.intel.com

In Linux 4.3-rc5, there is an error case in drm_dp_get_branch_device
that returns without releasing mgr->lock, resulting a spew of kernel
messages about a kernel work function possibly having leaked a mutex
and presumably more serious adverse consequences later.  This patch
changes the error to "goto out" to unlock the mutex before returning.

[airlied: grabbed from drm-next as it fixes something we've seen]
Signed-off-by: NAdam J. Richter <adam_richter2004@yahoo.com>
Cc: stable@vger.kernel.org
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

In Linux 4.3-rc5, there is an error case in drm_dp_get_branch_device
that returns without releasing mgr->lock, resulting a spew of kernel
messages about a kernel work function possibly having leaked a mutex
and presumably more serious adverse consequences later.  This patch
changes the error to "goto out" to unlock the mutex before returning.
Signed-off-by: NAdam J. Richter <adam_richter2004@yahoo.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This zeroes the msg so no random stack data ends up getting
sent, it also limits the function to not accepting > 4
i2c msgs.

Cc: stable@vger.kernel.org
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

This just removes the magic number.
Acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Since 9eb1e57f
drm/dp/mst: make sure mst_primary mstb is valid in work function

we validate the mstb structs in the work function, and doing
that takes a reference. So we should never get here with the
work function running using the mstb device, only if the work
function hasn't run yet or is running for another mstb.

So we don't need to sync the work here, this was causing
lockdep spew as below.

[  +0.000160] =============================================
[  +0.000001] [ INFO: possible recursive locking detected ]
[  +0.000002] 3.10.0-320.el7.rhel72.stable.backport.3.x86_64.debug #1 Tainted: G        W      ------------
[  +0.000001] ---------------------------------------------
[  +0.000001] kworker/4:2/1262 is trying to acquire lock:
[  +0.000001]  ((&mgr->work)){+.+.+.}, at: [<ffffffff810b29a5>] flush_work+0x5/0x2e0
[  +0.000007]
but task is already holding lock:
[  +0.000001]  ((&mgr->work)){+.+.+.}, at: [<ffffffff810b57e4>] process_one_work+0x1b4/0x710
[  +0.000004]
other info that might help us debug this:
[  +0.000001]  Possible unsafe locking scenario:

[  +0.000002]        CPU0
[  +0.000000]        ----
[  +0.000001]   lock((&mgr->work));
[  +0.000002]   lock((&mgr->work));
[  +0.000001]
 *** DEADLOCK ***

[  +0.000001]  May be due to missing lock nesting notation

[  +0.000002] 2 locks held by kworker/4:2/1262:
[  +0.000001]  #0:  (events_long){.+.+.+}, at: [<ffffffff810b57e4>] process_one_work+0x1b4/0x710
[  +0.000004]  #1:  ((&mgr->work)){+.+.+.}, at: [<ffffffff810b57e4>] process_one_work+0x1b4/0x710
[  +0.000003]
stack backtrace:
[  +0.000003] CPU: 4 PID: 1262 Comm: kworker/4:2 Tainted: G        W      ------------   3.10.0-320.el7.rhel72.stable.backport.3.x86_64.debug #1
[  +0.000001] Hardware name: LENOVO 20EGS0R600/20EGS0R600, BIOS GNET71WW (2.19 ) 02/05/2015
[  +0.000008] Workqueue: events_long drm_dp_mst_link_probe_work [drm_kms_helper]
[  +0.000001]  ffffffff82c26c90 00000000a527b914 ffff88046399bae8 ffffffff816fe04d
[  +0.000004]  ffff88046399bb58 ffffffff8110f47f ffff880461438000 0001009b840fc003
[  +0.000002]  ffff880461438a98 0000000000000000 0000000804dc26e1 ffffffff824a2c00
[  +0.000003] Call Trace:
[  +0.000004]  [<ffffffff816fe04d>] dump_stack+0x19/0x1b
[  +0.000004]  [<ffffffff8110f47f>] __lock_acquire+0x115f/0x1250
[  +0.000002]  [<ffffffff8110fd49>] lock_acquire+0x99/0x1e0
[  +0.000002]  [<ffffffff810b29a5>] ? flush_work+0x5/0x2e0
[  +0.000002]  [<ffffffff810b29ee>] flush_work+0x4e/0x2e0
[  +0.000002]  [<ffffffff810b29a5>] ? flush_work+0x5/0x2e0
[  +0.000004]  [<ffffffff81025905>] ? native_sched_clock+0x35/0x80
[  +0.000002]  [<ffffffff81025959>] ? sched_clock+0x9/0x10
[  +0.000002]  [<ffffffff810da1f5>] ? local_clock+0x25/0x30
[  +0.000002]  [<ffffffff8110dca9>] ? mark_held_locks+0xb9/0x140
[  +0.000003]  [<ffffffff810b4ed5>] ? __cancel_work_timer+0x95/0x160
[  +0.000002]  [<ffffffff810b4ee8>] __cancel_work_timer+0xa8/0x160
[  +0.000002]  [<ffffffff810b4fb0>] cancel_work_sync+0x10/0x20
[  +0.000007]  [<ffffffffa0160d17>] drm_dp_destroy_mst_branch_device+0x27/0x120 [drm_kms_helper]
[  +0.000006]  [<ffffffffa0163968>] drm_dp_mst_link_probe_work+0x78/0xa0 [drm_kms_helper]
[  +0.000002]  [<ffffffff810b5850>] process_one_work+0x220/0x710
[  +0.000002]  [<ffffffff810b57e4>] ? process_one_work+0x1b4/0x710
[  +0.000005]  [<ffffffff810b5e5b>] worker_thread+0x11b/0x3a0
[  +0.000003]  [<ffffffff810b5d40>] ? process_one_work+0x710/0x710
[  +0.000002]  [<ffffffff810beced>] kthread+0xed/0x100
[  +0.000003]  [<ffffffff810bec00>] ? insert_kthread_work+0x80/0x80
[  +0.000003]  [<ffffffff817121d8>] ret_from_fork+0x58/0x90

v2: add flush_work.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

In order to cache the EDID properly for tiled displays, we
need to retrieve it before we register the connector with
userspace, otherwise userspace can call get resources
and try and get the edid before we've even cached it.

This fixes some problems when hotplugging mst monitors,
with X/mutter running. As mutter seems to get 0 modes
for one of the monitors in the tile.

v2: fix warning in radeon
handle tile setting in cached path rather than
get edid path.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

Update the state before sending the msg to close it.

v2: reset value if return indicates we haven't send the msg.
v3: just clean the code up.
Pointed out by Adam J Richter on

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91481Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

output ports should always have a connector, unless
in the rare case connector allocation fails in the
driver.

In this case we only need to teardown the pdt,
and free the struct, and there is no need to
send a hotplug msg.

In the case were we add the port to the destroy
list we need to send a hotplug if we destroy
any connectors, so userspace knows to reprobe
stuff.

this patch also handles port->connector allocation
failing which should be a rare event, but makes
the code consistent.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

This is unnecessary and it makes it easier to see what is needed
from port.

also add blank line to make things nicer.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

It appears some MST docks are worse than other, but the only
way to know is to see the sw revisions in here, so dump
the branch OUI so we can look at the sw revision.

v2: Thierry made me feel guilty, so I parsed the branch
OUI.
Reviewed-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

The port is removed synchronously, but the connector delayed.
This causes a use after free which can cause a kernel BUG with
slug_debug=FPZU. This is fixed by freeing the port after the
connector.

This fixes a regression introduced with
6b8eeca6
"drm/dp/mst: close deadlock in connector destruction."

Cc: stable@vger.kernel.org
Cc: Dave Airlie <airlied@redhat.com>
Signed-off-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

Apparently been in there since forever and fairly easy to hit when
hotplugging really fast. I can do that since my mst hub has a manual
button to flick the hpd line for reprobing. The resulting WARNING spam
isn't pretty.

Cc: Dave Airlie <airlied@gmail.com>
Cc: stable@vger.kernel.org
Reviewed-by: NThierry Reding <treding@nvidia.com>
Reviewed-by: NAnder Conselvan de Oliveira <conselvan2@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

I've only seen this once, and I failed to capture the
lockdep backtrace, but I did some investigations.

If we are calling into the MST layer from EDID probing,
we have the mode_config mutex held, if during that EDID
probing, the MST hub goes away, then we can get a deadlock
where the connector destruction function in the driver
tries to retake the mode config mutex.

This offloads connector destruction to a workqueue,
and avoid the subsequenct lock ordering issue.
Acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

If we are doing an MST transaction and we've gotten HPD and we
lookup the device from the incoming msg, we should take the mgr
lock around it, so that mst_primary and mstb->ports are valid.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

This validates the mst_primary under the lock, and then calls
into the check and send function. This makes the code a lot
easier to understand the locking rules in.
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

radeon requires this to get the slots for later filling
out a table on every transition.
Signed-off-by: NDave Airlie <airlied@redhat.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

With drm-next, we can get a backtrace from sleeping
with mutex detection.

this is due to the callback checking the txmsg state taking
the mutex, which can cause a sleep inside a sleep,

Daniel went over it and was happy we could drop this mutex
in this case.
Signed-off-by: NDave Airlie <airlied@redhat.com>

This takes the tiling info from the connector and
exposes it to userspace, as a blob object in a
connector property.

The contents of the blob is ABI.

v2: add property + function documentation.

v3: move property setup from previous patch.
add boilerplate + fix long line (Daniel)
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Logical ports are never going to have EDID changes,
they are used for the internal ports on MST monitors.

We cache the EDIDs from these to save time at MST probe.

v2: drop misplace tile property line, meant for other patch.
Signed-off-by: NDave Airlie <airlied@redhat.com>

When we unplug a dp mst branch we unreference the entire tree from
the root towards the leaves. Which is ok, since that's the way the
pointers and so also the refcounts go.

But when we drop the reference we must make sure that we remove the
branches/ports from the lists/pointers before dropping the reference.
Otherwise the get_validated functions will still return it instead
of returning NULL (which indicates a potentially on-going unplug).

The mst branch destroy gets this right for ports: First it deletes
the port from the ports list, then it unrefs. But the ports destroy
function gets it wrong: First it unrefs, then it drops the ref. Which
means a zombie mst branch can still be validate with get_validated_mstb_ref
when it shouldn't.

Fix this.

This should address a backtrace Dave dug out somewhere on unplug:

 [<ffffffffa00cc262>] drm_dp_mst_get_validated_mstb_ref_locked+0x92/0xa0 [drm_kms_helper]
 [<ffffffffa00cc211>] drm_dp_mst_get_validated_mstb_ref_locked+0x41/0xa0 [drm_kms_helper]
 [<ffffffffa00cc2aa>] drm_dp_get_validated_mstb_ref+0x3a/0x60 [drm_kms_helper]
 [<ffffffffa00cc2fb>] drm_dp_payload_send_msg.isra.14+0x2b/0x100 [drm_kms_helper]
 [<ffffffffa00cc547>] drm_dp_update_payload_part1+0x177/0x360 [drm_kms_helper]
 [<ffffffffa015c52e>] intel_mst_disable_dp+0x3e/0x80 [i915]
 [<ffffffffa013d60b>] haswell_crtc_disable+0x1cb/0x340 [i915]
 [<ffffffffa0136739>] intel_crtc_control+0x49/0x100 [i915]
 [<ffffffffa0136857>] intel_crtc_update_dpms+0x67/0x80 [i915]
 [<ffffffffa013fa59>] intel_connector_dpms+0x59/0x70 [i915]
 [<ffffffffa015c752>] intel_dp_destroy_mst_connector+0x32/0xc0 [i915]
 [<ffffffffa00cb44b>] drm_dp_destroy_port+0x6b/0xa0 [drm_kms_helper]
 [<ffffffffa00cb588>] drm_dp_destroy_mst_branch_device+0x108/0x130 [drm_kms_helper]
 [<ffffffffa00cb3cd>] drm_dp_port_teardown_pdt+0x3d/0x50 [drm_kms_helper]
 [<ffffffffa00cdb79>] drm_dp_mst_handle_up_req+0x499/0x540 [drm_kms_helper]
 [<ffffffff810d9ead>] ? trace_hardirqs_on_caller+0x15d/0x200 [<ffffffffa00cdc73>]
 drm_dp_mst_hpd_irq+0x53/0xa00 [drm_kms_helper] [<ffffffffa00c7dfb>]
 ? drm_dp_dpcd_read+0x1b/0x20 [drm_kms_helper] [<ffffffffa0153ed8>]
 ? intel_dp_dpcd_read_wake+0x38/0x70 [i915] [<ffffffffa015a225>]
 intel_dp_check_mst_status+0xb5/0x250 [i915] [<ffffffffa015ac71>]
 intel_dp_hpd_pulse+0x181/0x210 [i915] [<ffffffffa01104f6>]
 i915_digport_work_func+0x96/0x120 [i915]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

Don't BUG out if the link reports an invalid (or plain unknown)
bandwidth value, but report the failure and fail gracefully.

Fixes a trivial compiler warning in case the BUG is ever compiled away.

Link: http://lkml.kernel.org/p/1415785566-12758-1-git-send-email-geert@linux-m68k.orgSigned-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Fixed wrong usage of strncat, switched to strlcpy.
While sending the string size to function to reduce
the potential for misuse in future.
Signed-off-by: NRickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The old code has problems with the Dell MST monitors due to some
assumptions I made that weren't true.

I initially thought the Virtual Channel Payload IDs had to be in
the DPCD table in ascending order, however it appears that assumption
is bogus.

The old code also assumed it was possible to insert a member
into the table and it would move other members up, like it does
when you remove table entries, however reality has shown this
isn't true.

So the new code allocates VCPIs separate from entries in the payload
tracking table, and when we remove an entry from the DPCD table,
I shuffle the tracking payload entries around in the struct.

This appears to make VT switch more robust (still not perfect)
with an MST enabled Dell monitor.
Signed-off-by: NDave Airlie <airlied@redhat.com>