Index: sys/dev/pci/aceride.c
===================================================================
RCS file: /cvsroot/src/sys/dev/pci/aceride.c,v
retrieving revision 1.37
diff -u -p -r1.37 aceride.c
--- sys/dev/pci/aceride.c	21 Jul 2017 21:01:13 -0000	1.37
+++ sys/dev/pci/aceride.c	16 Aug 2020 14:51:11 -0000
@@ -298,6 +298,13 @@ acer_setup_channel(struct ata_channel *c
 		    ACER_UDMA_EN(chp->ch_channel, drive) |
 		    ACER_UDMA_TIM(chp->ch_channel, drive, 0x7));
 
+		/* (U)DMA doesn't work with ATAPI devices */
+		if (drvp->drive_type == ATA_DRIVET_ATAPI) {
+			s = splbio();
+			drvp->drive_flags &= ~(ATA_DRIVE_DMA|ATA_DRIVE_UDMA);
+			splx(s);
+		}
+
 		/* add timing values, setup DMA if needed */
 		if ((drvp->drive_flags & ATA_DRIVE_DMA) == 0 &&
 		    (drvp->drive_flags & ATA_DRIVE_UDMA) == 0) {