drm/amd/display: Optimize cursor position updates

[why]
Updating the cursor enablement register can be a slow operation and accumulates
when high polling rate cursors cause frequent updates asynchronously to the
cursor position.

[how]
Since the cursor enable bit is cached there is no need to update the
enablement register if there is no change to it.  This removes the
read-modify-write from the cursor position programming path in HUBP and
DPP, leaving only the register writes.

Reviewed-by: Josip Pavic <josip.pavic@amd.com>
Signed-off-by: Aric Cyr <Aric.Cyr@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dpp/dcn10/dcn10_dpp.c

@@ -480,10 +480,11 @@ void dpp1_set_cursor_position(
 	if (src_y_offset + cursor_height <= 0)
 		cur_en = 0;  /* not visible beyond top edge*/
 
-	REG_UPDATE(CURSOR0_CONTROL,
-			CUR0_ENABLE, cur_en);
+	if (dpp_base->pos.cur0_ctl.bits.cur0_enable != cur_en) {
+		REG_UPDATE(CURSOR0_CONTROL, CUR0_ENABLE, cur_en);
 
-	dpp_base->pos.cur0_ctl.bits.cur0_enable = cur_en;
+		dpp_base->pos.cur0_ctl.bits.cur0_enable = cur_en;
+	}
 }
 
 void dpp1_cnv_set_optional_cursor_attributes(

drivers/gpu/drm/amd/display/dc/dpp/dcn401/dcn401_dpp_cm.c

@@ -154,9 +154,11 @@ void dpp401_set_cursor_position(
 	struct dcn401_dpp *dpp = TO_DCN401_DPP(dpp_base);
 	uint32_t cur_en = pos->enable ? 1 : 0;
 
-	REG_UPDATE(CURSOR0_CONTROL, CUR0_ENABLE, cur_en);
+	if (dpp_base->pos.cur0_ctl.bits.cur0_enable != cur_en) {
+		REG_UPDATE(CURSOR0_CONTROL, CUR0_ENABLE, cur_en);
 
-	dpp_base->pos.cur0_ctl.bits.cur0_enable = cur_en;
+		dpp_base->pos.cur0_ctl.bits.cur0_enable = cur_en;
+	}
 }
 
 void dpp401_set_optional_cursor_attributes(

drivers/gpu/drm/amd/display/dc/hubp/dcn20/dcn20_hubp.c

@@ -1058,11 +1058,13 @@ void hubp2_cursor_set_position(
 	if (src_y_offset + cursor_height <= 0)
 		cur_en = 0;  /* not visible beyond top edge*/
 
-	if (cur_en && REG_READ(CURSOR_SURFACE_ADDRESS) == 0)
-		hubp->funcs->set_cursor_attributes(hubp, &hubp->curs_attr);
+	if (hubp->pos.cur_ctl.bits.cur_enable != cur_en) {
+		if (cur_en && REG_READ(CURSOR_SURFACE_ADDRESS) == 0)
+			hubp->funcs->set_cursor_attributes(hubp, &hubp->curs_attr);
 
-	REG_UPDATE(CURSOR_CONTROL,
+		REG_UPDATE(CURSOR_CONTROL,
 			CURSOR_ENABLE, cur_en);
+	}
 
 	REG_SET_2(CURSOR_POSITION, 0,
 			CURSOR_X_POSITION, pos->x,

drivers/gpu/drm/amd/display/dc/hubp/dcn401/dcn401_hubp.c

@@ -730,11 +730,13 @@ void hubp401_cursor_set_position(
 			dc_fixpt_from_int(dst_x_offset),
 			param->h_scale_ratio));
 
-	if (cur_en && REG_READ(CURSOR_SURFACE_ADDRESS) == 0)
-		hubp->funcs->set_cursor_attributes(hubp, &hubp->curs_attr);
+	if (hubp->pos.cur_ctl.bits.cur_enable != cur_en) {
+		if (cur_en && REG_READ(CURSOR_SURFACE_ADDRESS) == 0)
+			hubp->funcs->set_cursor_attributes(hubp, &hubp->curs_attr);
 
-	REG_UPDATE(CURSOR_CONTROL,
-		CURSOR_ENABLE, cur_en);
+		REG_UPDATE(CURSOR_CONTROL,
+			CURSOR_ENABLE, cur_en);
+	}
 
 	REG_SET_2(CURSOR_POSITION, 0,
 		CURSOR_X_POSITION, x_pos,