--- 02_pdc_micro/drivers/scsi/pata_pdc2027x.c	2005-08-03 15:44:16.000000000 +0800
+++ 03_pdc_atapi_dma/drivers/scsi/pata_pdc2027x.c	2005-08-05 00:41:53.000000000 +0800
@@ -29,7 +29,7 @@
 #include <asm/io.h>
 
 #define DRV_NAME	"pata_pdc2027x"
-#define DRV_VERSION	"0.71"
+#define DRV_VERSION	"0.72"
 #undef PDC_DEBUG
 
 #ifdef PDC_DEBUG
@@ -467,11 +467,40 @@
 static int pdc2027x_check_atapi_dma(struct ata_queued_cmd *qc)
 {
 	struct scsi_cmnd *cmd = qc->scsicmd;
-	int rc = 0;
+	u8 *scsicmd = cmd->cmnd;
+	int rc = 1; /* atapi dma off by default */
+	u32 lba;
 
-	/* pdc2027x can only do ATAPI DMA for specific buffer size */
-	if (cmd->request_bufflen % 256)
-		rc = 1;
+	/*
+	 * pdc2027x might lost irq if ATAPI DMA is used
+	 * for commands not in the white list.
+	 */
+	switch (scsicmd[0]) {
+	case READ_10:
+	case READ_12:
+	case READ_6:
+	case WRITE_12:
+	case WRITE_6:
+	case 0xad: /* READ_DVD_STRUCTURE */
+	case 0xbe: /* READ_CD */
+		/* ATAPI DMA is ok */
+		rc = 0;
+		break;
+	case WRITE_10:
+		/* LBA -45150 (FFFF4FA2h) to 
+		 * -1 (FFFFFFFFh) shall use PIO mode
+		 */
+		lba = (scsicmd[2] << 24) | (scsicmd[3] << 16) |
+			(scsicmd[4] << 8) | scsicmd[5]; 
+
+		if (lba < 0xffff4fa2)
+			/* ATAPI DMA is ok */
+			rc = 0;
+
+		break;
+	default:
+		;
+	}
 
 	return rc;
 }