disp: msm: add api to get active status of hw blocks

This change introduces new ctl path api read_active_status to check
if a particular hw block is active or not in the current control path.
This is specially required in continuous splash use case when bootloader
has programmed certain blocks and the kernel driver tries to find
out the same configuration. This is used to ascertain which DSC block
is active in continuous splash case since DSC blocks are not tied to
mixer blocks.

Change-Id: I8dd590aa2dc764bd340727c166e1133ef9ce7af5
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>

msm/sde/sde_hw_ctl.h

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
- * Copyright (c) 2015-2019, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2015-2020, The Linux Foundation. All rights reserved.
  */
 
 #ifndef _SDE_HW_CTL_H
@@ -435,6 +435,17 @@ struct sde_hw_ctl_ops {
 	 */
 	u32 (*read_ctl_layers)(struct sde_hw_ctl *ctx, int index);
 
+	/**
+	 * read active register configuration for this block
+	 * @ctx       : ctl path ctx pointer
+	 * @blk       : hw blk type, supported blocks are DSC, MERGE_3D, INTF,
+	 *              CDM, WB
+	 * @index     : blk index
+	 * @return    : true if blk at idx is active or false
+	 */
+	bool (*read_active_status)(struct sde_hw_ctl *ctx,
+			enum sde_hw_blk_type blk, int index);
+
 	/**
 	 * Set all blend stages to disabled
 	 * @ctx       : ctl path ctx pointer