--- 02_pdc_long/drivers/scsi/pata_pdc2027x.c	2005-08-12 11:39:32.000000000 +0800
+++ 03_pdc_lost_irq/drivers/scsi/pata_pdc2027x.c	2005-08-12 15:04:09.000000000 +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 +467,30 @@
 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 */
 
-	/* pdc2027x can only do ATAPI DMA for specific buffer size */
-	if (cmd->request_bufflen % 256)
-		rc = 1;
+	/*
+	 * This workaround is from Promise's GPL driver.
+	 * If ATAPI DMA is used for commands not in the 
+	 * following white list, say MODE_SENSE and REQUEST_SENSE,
+	 * pdc2027x might hit the irq lost problem.
+	 */
+	switch (scsicmd[0]) {
+	case READ_10:
+	case WRITE_10:
+	case READ_12:
+	case WRITE_12:
+	case READ_6:
+	case WRITE_6:
+	case 0xad: /* READ_DVD_STRUCTURE */
+	case 0xbe: /* READ_CD */
+		/* ATAPI DMA is ok */
+		rc = 0;
+		break;
+	default:
+		;
+	}
 
 	return rc;
 }