v4l: xilinx: dprx: Generate HPD interrupt in unplug handler

When the unplug handler is called, bring down the HPD signal for 750us to
generate HPD interrupt so the source can train the link again based on
the link status.

Signed-off-by: Rajesh Gugulothu <gugulothu.rajesh@xilinx.com>
Reviewed-by: Vishal Sagar <vishal.sagar@xilinx.com>

drivers/media/platform/xilinx/xilinx-dprxss.c

@@ -205,6 +205,10 @@
 #define DP_LINK_BW_5_4G		5400    /* 1.2 */
 #define DP_LINK_BW_8_1G		8100    /* 1.4 */
 
+#define xdprxss_generate_hpd_intr(state, duration) \
+		xdprxss_write(state, XDPRX_HPD_INTR_REG, \
+			      FIELD_PREP(XDPRX_HPD_PULSE_MASK, duration) |\
+			      XDPRX_HPD_INTR_MASK)
 #define xdprxss_disable_unplug_intr(state) \
 		xdprxss_set(state, XDPRX_INTR_MASK_REG, XDPRX_INTR_UNPLUG_MASK)
 
@@ -814,6 +818,7 @@ static void xdprxss_irq_unplug(struct xdprxss_state *state)
 	 * disconnected
 	 */
 	xdprxss_disable_unplug_intr(state);
+	xdprxss_generate_hpd_intr(state, XDPRX_HPD_PULSE_750);
 
 	/*
 	 * In a scenario, where the cable is plugged-in but the training