drm/amd/display: Fix static checker warnings on tracebuff_fb

[Why]
Static analysis on linux-next has found a potential null pointer
dereference;

[How]
Refactor the function, add ASSERT and remove the unnecessary check.
Signed-off-by: Leo (Hanghong) Ma <hanghong.ma@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dmub/src/dmub_srv.c

@@ -415,6 +415,12 @@ enum dmub_status dmub_srv_hw_init(struct dmub_srv *dmub,
 	if (!dmub->sw_init)
 		return DMUB_STATUS_INVALID;
 
+	if (!inst_fb || !stack_fb || !data_fb || !bios_fb || !mail_fb ||
+		!tracebuff_fb || !fw_state_fb || !scratch_mem_fb) {
+		ASSERT(0);
+		return DMUB_STATUS_INVALID;
+	}
+
 	dmub->fb_base = params->fb_base;
 	dmub->fb_offset = params->fb_offset;
 	dmub->psp_version = params->psp_version;
@@ -422,7 +428,6 @@ enum dmub_status dmub_srv_hw_init(struct dmub_srv *dmub,
 	if (dmub->hw_funcs.reset)
 		dmub->hw_funcs.reset(dmub);
 
-	if (inst_fb && data_fb) {
 	cw0.offset.quad_part = inst_fb->gpu_addr;
 	cw0.region.base = DMUB_CW0_BASE;
 	cw0.region.top = cw0.region.base + inst_fb->size - 1;
@@ -441,10 +446,6 @@ enum dmub_status dmub_srv_hw_init(struct dmub_srv *dmub,
 		dmub->hw_funcs.backdoor_load(dmub, &cw0, &cw1);
 	}
 
-	}
-
-	if (inst_fb && data_fb && bios_fb && mail_fb && tracebuff_fb &&
-	    fw_state_fb && scratch_mem_fb) {
 	cw2.offset.quad_part = data_fb->gpu_addr;
 	cw2.region.base = DMUB_CW0_BASE + inst_fb->size;
 	cw2.region.top = cw2.region.base + data_fb->size;
@@ -476,7 +477,6 @@ enum dmub_status dmub_srv_hw_init(struct dmub_srv *dmub,
 	outbox0.base = DMUB_REGION5_BASE + TRACE_BUFFER_ENTRY_OFFSET;
 	outbox0.top = outbox0.base + tracebuff_fb->size - TRACE_BUFFER_ENTRY_OFFSET;
 
-
 	cw6.offset.quad_part = fw_state_fb->gpu_addr;
 	cw6.region.base = DMUB_CW6_BASE;
 	cw6.region.top = cw6.region.base + fw_state_fb->size;
@@ -486,8 +486,7 @@ enum dmub_status dmub_srv_hw_init(struct dmub_srv *dmub,
 	dmub->scratch_mem_fb = *scratch_mem_fb;
 
 	if (dmub->hw_funcs.setup_windows)
-			dmub->hw_funcs.setup_windows(dmub, &cw2, &cw3, &cw4,
-						     &cw5, &cw6);
+		dmub->hw_funcs.setup_windows(dmub, &cw2, &cw3, &cw4, &cw5, &cw6);
 
 	if (dmub->hw_funcs.setup_outbox0)
 		dmub->hw_funcs.setup_outbox0(dmub, &outbox0);
@@ -496,14 +495,11 @@ enum dmub_status dmub_srv_hw_init(struct dmub_srv *dmub,
 		dmub->hw_funcs.setup_mailbox(dmub, &inbox1);
 	if (dmub->hw_funcs.setup_out_mailbox)
 		dmub->hw_funcs.setup_out_mailbox(dmub, &outbox1);
-	}
 
-	if (mail_fb) {
 	dmub_memset(&rb_params, 0, sizeof(rb_params));
 	rb_params.ctx = dmub;
 	rb_params.base_address = mail_fb->cpu_addr;
 	rb_params.capacity = DMUB_RB_SIZE;
-
 	dmub_rb_init(&dmub->inbox1_rb, &rb_params);
 
 	// Initialize outbox1 ring buffer
@@ -512,8 +508,6 @@ enum dmub_status dmub_srv_hw_init(struct dmub_srv *dmub,
 	rb_params.capacity = DMUB_RB_SIZE;
 	dmub_rb_init(&dmub->outbox1_rb, &rb_params);
 
-	}
-
 	dmub_memset(&outbox0_rb_params, 0, sizeof(outbox0_rb_params));
 	outbox0_rb_params.ctx = dmub;
 	outbox0_rb_params.base_address = (void *)((uint64_t)(tracebuff_fb->cpu_addr) + TRACE_BUFFER_ENTRY_OFFSET);