[ide] ide-cd: fix possible race in PIO mode

From: Alan Cox <alan@lxorguk.ukuu.org.uk>

When we issue an ide command the status bits don't become valid for
400nS. In the DMA case ide_execute_command handles this but in the PIO
case we don't do the needed locking, use OUTBSYNC to avoid posting or
delay. This means that in some situations we can execute the command
handler in PIO mode before the command status bits are valid and the
handler may read and act wrongly.
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide-cd.c

@@ -890,8 +890,14 @@ static ide_startstop_t cdrom_start_packet_command(ide_drive_t *drive,
 		ide_execute_command(drive, WIN_PACKETCMD, handler, ATAPI_WAIT_PC, cdrom_timer_expiry);
 		return ide_started;
 	} else {
+		unsigned long flags;
+
 		/* packet command */
-		HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
+		spin_lock_irqsave(&ide_lock, flags);
+		hwif->OUTBSYNC(drive, WIN_PACKETCMD, IDE_COMMAND_REG);
+		ndelay(400);
+		spin_unlock_irqrestore(&ide_lock, flags);
+
 		return (*handler) (drive);
 	}
 }