macintosh/adb-iop: Adopt bus reset algorithm from via-macii driver

This algorithm is slightly shorter and avoids the surprising
adb_iop_start() call in adb_iop_poll().

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b63d56ecb6e75f11a0bf02231f3b2db656a528a3.1590880623.git.fthain@telegraphics.com.au

drivers/macintosh/adb-iop.c

@@ -238,24 +238,19 @@ int adb_iop_autopoll(int devs)
 
 void adb_iop_poll(void)
 {
-	if (adb_iop_state == idle)
-		adb_iop_start();
 	iop_ism_irq_poll(ADB_IOP);
 }
 
 int adb_iop_reset_bus(void)
 {
-	struct adb_request req = {
-		.reply_expected = 0,
-		.nbytes = 2,
-		.data = { ADB_PACKET, 0 },
-	};
+	struct adb_request req;
 
-	adb_iop_write(&req);
-	while (!req.complete) {
-		adb_iop_poll();
-		schedule();
-	}
+	/* Command = 0, Address = ignored */
+	adb_request(&req, NULL, ADBREQ_NOSEND, 1, ADB_BUSRESET);
+	adb_iop_send_request(&req, 1);
+
+	/* Don't want any more requests during the Global Reset low time. */
+	mdelay(3);
 
 	return 0;
 }