drm/i915/ddi: Optimize mtl_port_buf_ctl_program

A small optimization and cleanup for mtl_port_buf_ctl_program function
which lets use intel_de_rmw instead of a intel_de_read and
intel_de_write.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250103051705.145161-3-suraj.kandpal@intel.com

Author: surajk8

drivers/gpu/drm/i915/display/intel_ddi.c

@@ -2537,13 +2537,10 @@ static void mtl_port_buf_ctl_program(struct intel_encoder *encoder,
 	struct intel_display *display = to_intel_display(encoder);
 	struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
 	enum port port = encoder->port;
-	u32 val;
+	u32 val = 0;
 
-	val = intel_de_read(display, XELPDP_PORT_BUF_CTL1(i915, port));
-	val &= ~XELPDP_PORT_WIDTH_MASK;
 	val |= XELPDP_PORT_WIDTH(mtl_get_port_width(crtc_state->lane_count));
 
-	val &= ~XELPDP_PORT_BUF_PORT_DATA_WIDTH_MASK;
 	if (intel_dp_is_uhbr(crtc_state))
 		val |= XELPDP_PORT_BUF_PORT_DATA_40BIT;
 	else
@@ -2552,7 +2549,9 @@ static void mtl_port_buf_ctl_program(struct intel_encoder *encoder,
 	if (dig_port->lane_reversal)
 		val |= XELPDP_PORT_REVERSAL;
 
-	intel_de_write(display, XELPDP_PORT_BUF_CTL1(display, port), val);
+	intel_de_rmw(display, XELPDP_PORT_BUF_CTL1(display, port),
+		     XELPDP_PORT_WIDTH_MASK | XELPDP_PORT_BUF_PORT_DATA_WIDTH_MASK,
+		     val);
 }
 
 static void mtl_port_buf_ctl_io_selection(struct intel_encoder *encoder)