drm/i915/mtl: Cleanup usage of phy lane reset

From PICA message bus we wait for acknowledgment from
read/write commands. In case of an error, we reset the
bus for the next command.

Current implementation ends up resetting message bus twice
in cases where error is not the timeout. Since, we only need
to reset message bus once, let's move reset to corresponding
timeout error and drop the excess reset function calls from
read/write functions.

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230609122130.69794-1-mika.kahola@intel.com

drivers/gpu/drm/i915/display/intel_cx0_phy.c

@@ -116,6 +116,7 @@ static int intel_cx0_wait_for_ack(struct drm_i915_private *i915, enum port port,
 					 XELPDP_MSGBUS_TIMEOUT_SLOW, val)) {
 		drm_dbg_kms(&i915->drm, "PHY %c Timeout waiting for message ACK. Status: 0x%x\n",
 			    phy_name(phy), *val);
+		intel_cx0_bus_reset(i915, port, lane);
 		return -ETIMEDOUT;
 	}
 
@@ -158,10 +159,8 @@ static int __intel_cx0_read_once(struct drm_i915_private *i915, enum port port,
 		       XELPDP_PORT_M2P_ADDRESS(addr));
 
 	ack = intel_cx0_wait_for_ack(i915, port, XELPDP_PORT_P2M_COMMAND_READ_ACK, lane, &val);
-	if (ack < 0) {
-		intel_cx0_bus_reset(i915, port, lane);
+	if (ack < 0)
 		return ack;
-	}
 
 	intel_clear_response_ready_flag(i915, port, lane);
 
@@ -202,6 +201,7 @@ static int __intel_cx0_write_once(struct drm_i915_private *i915, enum port port,
 				  int lane, u16 addr, u8 data, bool committed)
 {
 	enum phy phy = intel_port_to_phy(i915, port);
+	int ack;
 	u32 val;
 
 	if (intel_de_wait_for_clear(i915, XELPDP_PORT_M2P_MSGBUS_CTL(port, lane),
@@ -230,10 +230,9 @@ static int __intel_cx0_write_once(struct drm_i915_private *i915, enum port port,
 	}
 
 	if (committed) {
-		if (intel_cx0_wait_for_ack(i915, port, XELPDP_PORT_P2M_COMMAND_WRITE_ACK, lane, &val) < 0) {
-			intel_cx0_bus_reset(i915, port, lane);
-			return -EINVAL;
-		}
+		ack = intel_cx0_wait_for_ack(i915, port, XELPDP_PORT_P2M_COMMAND_WRITE_ACK, lane, &val);
+		if (ack < 0)
+			return ack;
 	} else if ((intel_de_read(i915, XELPDP_PORT_P2M_MSGBUS_STATUS(port, lane)) &
 		    XELPDP_PORT_P2M_ERROR_SET)) {
 		drm_dbg_kms(&i915->drm,