libata: Add a drivers/ide style DMA disable

This is useful when debugging, handling problem systems, or for
distributions just to get the system installed so it can be sorted
out later.

This is a bit smarter than the old IDE one and lets you do

libata.dma=0	Disable all PATA DMA like old IDE
libata.dma=1	Disk DMA only
libata.dma=2	ATAPI DMA only
libata.dma=4	CF DMA only

(or combinations thereof - 0,1,3 being the useful ones I suspect)

(I've split CF as it seems to be a seperate case of pain and suffering
different to the others and caused by assorted PIO wired adapters etc)
Signed-off-by: Alan Cox <alan@redhat.com>

[edited to work on SATA too, changing name from 'pata_dma' to 'dma']
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/libata-core.c

@@ -97,6 +97,10 @@ static int ata_ignore_hpa = 0;
 module_param_named(ignore_hpa, ata_ignore_hpa, int, 0644);
 MODULE_PARM_DESC(ignore_hpa, "Ignore HPA limit (0=keep BIOS limits, 1=ignore limits, using full disk)");
 
+static int libata_dma_mask = ATA_DMA_MASK_ATA|ATA_DMA_MASK_ATAPI|ATA_DMA_MASK_CFA;
+module_param_named(dma, libata_dma_mask, int, 0444);
+MODULE_PARM_DESC(dma, "DMA enable/disable (0x1==ATA, 0x2==ATAPI, 0x4==CF)");
+
 static int ata_probe_timeout = ATA_TMOUT_INTERNAL / HZ;
 module_param(ata_probe_timeout, int, 0444);
 MODULE_PARM_DESC(ata_probe_timeout, "Set ATA probing timeout (seconds)");
@@ -2917,14 +2921,27 @@ int ata_do_set_mode(struct ata_link *link, struct ata_device **r_failed_dev)
 	/* step 1: calculate xfer_mask */
 	ata_link_for_each_dev(dev, link) {
 		unsigned int pio_mask, dma_mask;
+		unsigned int mode_mask;
 
 		if (!ata_dev_enabled(dev))
 			continue;
 
+		mode_mask = ATA_DMA_MASK_ATA;
+		if (dev->class == ATA_DEV_ATAPI)
+			mode_mask = ATA_DMA_MASK_ATAPI;
+		else if (ata_id_is_cfa(dev->id))
+			mode_mask = ATA_DMA_MASK_CFA;
+
 		ata_dev_xfermask(dev);
 
 		pio_mask = ata_pack_xfermask(dev->pio_mask, 0, 0);
 		dma_mask = ata_pack_xfermask(0, dev->mwdma_mask, dev->udma_mask);
+
+		if (libata_dma_mask & mode_mask)
+			dma_mask = ata_pack_xfermask(0, dev->mwdma_mask, dev->udma_mask);
+		else
+			dma_mask = 0;
+
 		dev->pio_mode = ata_xfer_mask2mode(pio_mask);
 		dev->dma_mode = ata_xfer_mask2mode(dma_mask);
 

include/linux/libata.h

@@ -331,6 +331,12 @@ enum {
 	ATA_HORKAGE_BROKEN_HPA	= (1 << 4),	/* Broken HPA */
 	ATA_HORKAGE_SKIP_PM	= (1 << 5),	/* Skip PM operations */
 	ATA_HORKAGE_HPA_SIZE	= (1 << 6),	/* native size off by one */
+
+	 /* DMA mask for user DMA control: User visible values; DO NOT 
+	    renumber */
+	ATA_DMA_MASK_ATA	= (1 << 0),	/* DMA on ATA Disk */
+	ATA_DMA_MASK_ATAPI	= (1 << 1),	/* DMA on ATAPI */
+	ATA_DMA_MASK_CFA	= (1 << 2),	/* DMA on CF Card */
 };
 
 enum hsm_task_states {