drm/amd/display: Copy GSL groups when committing a new context

[Why]
DC configures the GSL group for the pipe when pipe_split is enabled
and we're switching flip types (buffered <-> immediate flip) on DCN2.

In order to record what GSL group the pipe is using DC stores it in
the pipe's stream_res. DM is not aware of this internal grouping, nor
is DC resource.

So when DM creates a dc_state context and passes it to DC the current
GSL group is lost - DM never knew about it in the first place.

After 3 immediate flips we run out of GSL groups and we're no longer
able to correctly perform *any* flip for multi-pipe scenarios.

[How]
The gsl_group needs to be copied to the new context.

DM has no insight into GSL grouping and could even potentially create
a brand new context without referencing current hardware state. So this
makes the most sense to have happen in DC.

There are two places where DC can apply a new context:
- dc_commit_state
- dc_commit_updates_for_stream

But what's shared between both of these is apply_ctx_for_surface.

This logic only matters for DCN2, so it can be placed in
dcn20_apply_ctx_for_surface. Before doing any locking (where the GSL
group is setup) we can copy over the GSL groups before committing the
new context.

Signed-off-by: Nicholas Kazlauskas <[e-mail]>
Reviewed-by: Hersen Wu <[e-mail]>
Acked-by: Leo Li <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c

···
 	if (!top_pipe_to_program)
 		return;
 
+	/* Carry over GSL groups in case the context is changing. */
+	for (i = 0; i < dc->res_pool->pipe_count; i++) {
+		struct pipe_ctx *pipe_ctx = &context->res_ctx.pipe_ctx[i];
+		struct pipe_ctx *old_pipe_ctx =
+			&dc->current_state->res_ctx.pipe_ctx[i];
+
+		if (pipe_ctx->stream == stream &&
+		    pipe_ctx->stream == old_pipe_ctx->stream)
+			pipe_ctx->stream_res.gsl_group =
+				old_pipe_ctx->stream_res.gsl_group;
+	}
+
 	tg = top_pipe_to_program->stream_res.tg;
 
 	interdependent_update = top_pipe_to_program->plane_state &&