pata_cypress: add a module option to disable BM-DMA

Multiple users report that they need to disable DMA on this driver,
so provide an option to do so without affecting all of libata.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20210616134658.1471835-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/ata/pata_cypress.c

@@ -41,6 +41,10 @@ enum {
 	CY82_INDEX_TIMEOUT	= 0x32
 };
 
+static bool enable_dma = true;
+module_param(enable_dma, bool, 0);
+MODULE_PARM_DESC(enable_dma, "Enable bus master DMA operations");
+
 /**
  *	cy82c693_set_piomode	-	set initial PIO mode data
  *	@ap: ATA interface
@@ -124,14 +128,16 @@ static struct ata_port_operations cy82c693_port_ops = {
 
 static int cy82c693_init_one(struct pci_dev *pdev, const struct pci_device_id *id)
 {
-	static const struct ata_port_info info = {
+	static struct ata_port_info info = {
 		.flags = ATA_FLAG_SLAVE_POSS,
 		.pio_mask = ATA_PIO4,
-		.mwdma_mask = ATA_MWDMA2,
 		.port_ops = &cy82c693_port_ops
 	};
 	const struct ata_port_info *ppi[] = { &info, &ata_dummy_port_info };
 
+	if (enable_dma)
+		info.mwdma_mask = ATA_MWDMA2;
+
 	/* Devfn 1 is the ATA primary. The secondary is magic and on devfn2.
 	   For the moment we don't handle the secondary. FIXME */