drm/mst: rework payload table allocation to conform better.

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: Dave Airlie <airlied@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 9b446ad..338fc10 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -388,6 +388,7 @@ struct drm_dp_payload {
 	int payload_state;
 	int start_slot;
 	int num_slots;
+	int vcpi;
 };
 
 /**
@@ -454,6 +455,7 @@ struct drm_dp_mst_topology_mgr {
 	struct drm_dp_vcpi **proposed_vcpis;
 	struct drm_dp_payload *payloads;
 	unsigned long payload_mask;
+	unsigned long vcpi_mask;
 
 	wait_queue_head_t tx_waitq;
 	struct work_struct work;