drm/bridge: analogix_dp: only read AUX status when an error occured

All AUX error responses raise the AUX_ERR interrupt, so there is no
need to read the AUX status register in normal operation. Only read
the status when an error occurred and we can expect a different
status than OK.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240619182200.3752465-13-l.stach@pengutronix.de

drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c

@@ -924,7 +924,6 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
 			     struct drm_dp_aux_msg *msg)
 {
 	u32 reg;
-	u32 status_reg;
 	u8 *buffer = msg->buffer;
 	unsigned int i;
 	int ret;
@@ -1011,12 +1010,14 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
 
 	/* Clear interrupt source for AUX CH access error */
 	reg = readl(dp->reg_base + ANALOGIX_DP_INT_STA);
-	status_reg = readl(dp->reg_base + ANALOGIX_DP_AUX_CH_STA);
-	if ((reg & AUX_ERR) || (status_reg & AUX_STATUS_MASK)) {
+	if ((reg & AUX_ERR)) {
+		u32 aux_status = readl(dp->reg_base + ANALOGIX_DP_AUX_CH_STA) &
+				 AUX_STATUS_MASK;
+
 		writel(AUX_ERR, dp->reg_base + ANALOGIX_DP_INT_STA);
 
 		dev_warn(dp->dev, "AUX CH error happened: %#x (%d)\n",
-			 status_reg & AUX_STATUS_MASK, !!(reg & AUX_ERR));
+			 aux_status, !!(reg & AUX_ERR));
 		goto aux_error;
 	}