disp: msm: sde: handle LTM switch in and out of dual pipe merge mode

When LTM is switching on/off, merge_mode bit value gets toggled between
0x1 (dual pipe merge configuration) and 0x0 (single pipe configuration).
It is illegal to reconfigure LTM to/from dual-pipe merge mode before
both LTM instances have completed their current workloads. This change
adds support to disable merge_mode one frame after histogram is disabled
to make sure both hardware instances are completely idle and avoid
corrupted histogram data collection.

Change-Id: I9a6b5cbfb69e8af7936749e57fe7c8f7c2703b95
Signed-off-by: Ping Li <pingli@codeaurora.org>

msm/sde/sde_hw_dspp.h

@@ -210,6 +210,12 @@ struct sde_hw_dspp_ops {
 	 */
 	void (*ltm_read_intr_status)(struct sde_hw_dspp *ctx, u32 *status);
 
+	/**
+	 * clear_ltm_merge_mode - clear LTM merge_mode bit
+	 * @ctx: Pointer to dspp context
+	 */
+	void (*clear_ltm_merge_mode)(struct sde_hw_dspp *ctx);
+
 	/**
 	 * validate_rc_mask -  Validate RC mask configuration
 	 * @ctx: Pointer to dspp context.