drm/bridge: analogix_dp: handle AUX transfer timeouts

Timeouts on the AUX bus are to be expected in certain normal operating
conditions. There is no need to raise an error log or re-initialize the
whole AUX state machine. Simply acknowledge the AUX_ERR interrupt and
let upper layers know about the timeout.

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/20240619182200.3752465-14-l.stach@pengutronix.de

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

@@ -1016,6 +1016,9 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
 
 		writel(AUX_ERR, dp->reg_base + ANALOGIX_DP_INT_STA);
 
+		if (aux_status == AUX_STATUS_TIMEOUT_ERROR)
+			return -ETIMEDOUT;
+
 		dev_warn(dp->dev, "AUX CH error happened: %#x (%d)\n",
 			 aux_status, !!(reg & AUX_ERR));
 		goto aux_error;

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

@@ -361,6 +361,15 @@
 /* ANALOGIX_DP_AUX_CH_STA */
 #define AUX_BUSY				(0x1 << 4)
 #define AUX_STATUS_MASK				(0xf << 0)
+#define AUX_STATUS_OK				(0x0 << 0)
+#define AUX_STATUS_NACK_ERROR			(0x1 << 0)
+#define AUX_STATUS_TIMEOUT_ERROR		(0x2 << 0)
+#define AUX_STATUS_UNKNOWN_ERROR		(0x3 << 0)
+#define AUX_STATUS_MUCH_DEFER_ERROR		(0x4 << 0)
+#define AUX_STATUS_TX_SHORT_ERROR		(0x5 << 0)
+#define AUX_STATUS_RX_SHORT_ERROR		(0x6 << 0)
+#define AUX_STATUS_NACK_WITHOUT_M_ERROR		(0x7 << 0)
+#define AUX_STATUS_I2C_NACK_ERROR		(0x8 << 0)
 
 /* ANALOGIX_DP_AUX_CH_DEFER_CTL */
 #define DEFER_CTRL_EN				(0x1 << 7)