drm/amd/display: Move the memory allocation out of dcn20_validate_bandwidth_fp().

dcn20_validate_bandwidth_fp() is invoked while FPU access has been
enabled. FPU access requires disabling preemption even on PREEMPT_RT.
It is not possible to allocate memory with disabled preemption even with
GFP_ATOMIC on PREEMPT_RT.

Move the memory allocation before FPU access is enabled.
To preserve previous "clean" state of "pipes" add a memset() before the
second invocation of dcn20_validate_bandwidth_internal() where the
variable is used.
Acked-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

@@ -2141,9 +2141,17 @@ bool dcn20_validate_bandwidth(struct dc *dc, struct dc_state *context,
 		bool fast_validate)
 {
 	bool voltage_supported;
+	display_e2e_pipe_params_st *pipes;
+
+	pipes = kcalloc(dc->res_pool->pipe_count, sizeof(display_e2e_pipe_params_st), GFP_KERNEL);
+	if (!pipes)
+		return false;
+
 	DC_FP_START();
-	voltage_supported = dcn20_validate_bandwidth_fp(dc, context, fast_validate);
+	voltage_supported = dcn20_validate_bandwidth_fp(dc, context, fast_validate, pipes);
 	DC_FP_END();
+
+	kfree(pipes);
 	return voltage_supported;
 }
 

drivers/gpu/drm/amd/display/dc/dml/dcn20/dcn20_fpu.c

@@ -1925,7 +1925,7 @@ void dcn20_patch_bounding_box(struct dc *dc, struct _vcs_dpi_soc_bounding_box_st
 }
 
 static bool dcn20_validate_bandwidth_internal(struct dc *dc, struct dc_state *context,
-		bool fast_validate)
+		bool fast_validate, display_e2e_pipe_params_st *pipes)
 {
 	bool out = false;
 
@@ -1934,7 +1934,6 @@ static bool dcn20_validate_bandwidth_internal(struct dc *dc, struct dc_state *co
 	int vlevel = 0;
 	int pipe_split_from[MAX_PIPES];
 	int pipe_cnt = 0;
-	display_e2e_pipe_params_st *pipes = kzalloc(dc->res_pool->pipe_count * sizeof(display_e2e_pipe_params_st), GFP_ATOMIC);
 	DC_LOGGER_INIT(dc->ctx->logger);
 
 	BW_VAL_TRACE_COUNT();
@@ -1969,16 +1968,14 @@ static bool dcn20_validate_bandwidth_internal(struct dc *dc, struct dc_state *co
 	out = false;
 
 validate_out:
-	kfree(pipes);
 
 	BW_VAL_TRACE_FINISH();
 
 	return out;
 }
 
-bool dcn20_validate_bandwidth_fp(struct dc *dc,
-				 struct dc_state *context,
-				 bool fast_validate)
+bool dcn20_validate_bandwidth_fp(struct dc *dc, struct dc_state *context,
+				 bool fast_validate, display_e2e_pipe_params_st *pipes)
 {
 	bool voltage_supported = false;
 	bool full_pstate_supported = false;
@@ -1997,11 +1994,11 @@ bool dcn20_validate_bandwidth_fp(struct dc *dc,
 	ASSERT(context != dc->current_state);
 
 	if (fast_validate) {
-		return dcn20_validate_bandwidth_internal(dc, context, true);
+		return dcn20_validate_bandwidth_internal(dc, context, true, pipes);
 	}
 
 	// Best case, we support full UCLK switch latency
-	voltage_supported = dcn20_validate_bandwidth_internal(dc, context, false);
+	voltage_supported = dcn20_validate_bandwidth_internal(dc, context, false, pipes);
 	full_pstate_supported = context->bw_ctx.bw.dcn.clk.p_state_change_support;
 
 	if (context->bw_ctx.dml.soc.dummy_pstate_latency_us == 0 ||
@@ -2013,7 +2010,8 @@ bool dcn20_validate_bandwidth_fp(struct dc *dc,
 	// Fallback: Try to only support G6 temperature read latency
 	context->bw_ctx.dml.soc.dram_clock_change_latency_us = context->bw_ctx.dml.soc.dummy_pstate_latency_us;
 
-	voltage_supported = dcn20_validate_bandwidth_internal(dc, context, false);
+	memset(pipes, 0, dc->res_pool->pipe_count * sizeof(display_e2e_pipe_params_st));
+	voltage_supported = dcn20_validate_bandwidth_internal(dc, context, false, pipes);
 	dummy_pstate_supported = context->bw_ctx.bw.dcn.clk.p_state_change_support;
 
 	if (voltage_supported && (dummy_pstate_supported || !(context->stream_count))) {

drivers/gpu/drm/amd/display/dc/dml/dcn20/dcn20_fpu.h

@@ -61,9 +61,8 @@ void dcn20_update_bounding_box(struct dc *dc,
 			       unsigned int num_states);
 void dcn20_patch_bounding_box(struct dc *dc,
 			      struct _vcs_dpi_soc_bounding_box_st *bb);
-bool dcn20_validate_bandwidth_fp(struct dc *dc,
-				 struct dc_state *context,
-				 bool fast_validate);
+bool dcn20_validate_bandwidth_fp(struct dc *dc, struct dc_state *context,
+				 bool fast_validate, display_e2e_pipe_params_st *pipes);
 void dcn20_fpu_set_wm_ranges(int i,
 			     struct pp_smu_wm_range_sets *ranges,
 			     struct _vcs_dpi_soc_bounding_box_st *loaded_bb);