drm/amd/display: Increase timeout threshold for DMCUB reset

[Why]
If we're backdoor loading the DMCUB performs more work than just
the PHY reset so we can end up resetting before the cleanup has fully
finished.

[How]
Increase timeout, add udelay between spins to guarantee a minimum.
Reviewed-by: Roy Chan <roy.chan@amd.com>
Reviewed-by: Eric Yang <Eric.Yang2@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dmub/src/dmub_dcn31.c

@@ -83,7 +83,7 @@ static inline void dmub_dcn31_translate_addr(const union dmub_addr *addr_in,
 void dmub_dcn31_reset(struct dmub_srv *dmub)
 {
 	union dmub_gpint_data_register cmd;
-	const uint32_t timeout = 30;
+	const uint32_t timeout = 100;
 	uint32_t in_reset, scratch, i;
 
 	REG_GET(DMCUB_CNTL2, DMCUB_SOFT_RESET, &in_reset);
@@ -98,21 +98,21 @@ void dmub_dcn31_reset(struct dmub_srv *dmub)
 		/**
 		 * Timeout covers both the ACK and the wait
 		 * for remaining work to finish.
-		 *
-		 * This is mostly bound by the PHY disable sequence.
-		 * Each register check will be greater than 1us, so
-		 * don't bother using udelay.
 		 */
 
 		for (i = 0; i < timeout; ++i) {
 			if (dmub->hw_funcs.is_gpint_acked(dmub, cmd))
 				break;
+
+			udelay(1);
 		}
 
 		for (i = 0; i < timeout; ++i) {
 			scratch = dmub->hw_funcs.get_gpint_response(dmub);
 			if (scratch == DMUB_GPINT__STOP_FW_RESPONSE)
 				break;
+
+			udelay(1);
 		}
 
 		/* Force reset in case we timed out, DMCUB is likely hung. */