[libata] sata_svw: Disable ATAPI DMA on current boards (errata workaround)

Current Broadcom/Serverworks SATA boards (including Apple K2 SATA)
have problems with ATAPI DMA, so it is disabled.  ATAPI PIO, ATA PIO,
and ATA DMA continue to work just fine.
Acked-by: Anantha Subramanyam <ananth@broadcom.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/ata/sata_svw.c

@@ -56,6 +56,8 @@
 #define DRV_VERSION	"2.0"
 
 enum {
+	K2_FLAG_NO_ATAPI_DMA		= (1 << 29),
+
 	/* Taskfile registers offsets */
 	K2_SATA_TF_CMD_OFFSET		= 0x00,
 	K2_SATA_TF_DATA_OFFSET		= 0x00,
@@ -83,11 +85,33 @@ enum {
 
 	/* Port stride */
 	K2_SATA_PORT_OFFSET		= 0x100,
+
+	board_svw4			= 0,
+	board_svw8			= 1,
+};
+
+static const struct k2_board_info {
+	unsigned int		n_ports;
+	unsigned long		port_flags;
+} k2_board_info[] = {
+	/* board_svw4 */
+	{ 4, K2_FLAG_NO_ATAPI_DMA },
+
+	/* board_svw8 */
+	{ 8, K2_FLAG_NO_ATAPI_DMA },
 };
 
 static u8 k2_stat_check_status(struct ata_port *ap);
 
 
+static int k2_sata_check_atapi_dma(struct ata_queued_cmd *qc)
+{
+	if (qc->ap->flags & K2_FLAG_NO_ATAPI_DMA)
+		return -1;	/* ATAPI DMA not supported */
+
+	return 0;
+}
+
 static u32 k2_sata_scr_read (struct ata_port *ap, unsigned int sc_reg)
 {
 	if (sc_reg > SCR_CONTROL)
@@ -313,6 +337,7 @@ static const struct ata_port_operations k2_sata_ops = {
 	.check_status		= k2_stat_check_status,
 	.exec_command		= ata_exec_command,
 	.dev_select		= ata_std_dev_select,
+	.check_atapi_dma	= k2_sata_check_atapi_dma,
 	.bmdma_setup		= k2_bmdma_setup_mmio,
 	.bmdma_start		= k2_bmdma_start_mmio,
 	.bmdma_stop		= ata_bmdma_stop,
@@ -359,6 +384,8 @@ static int k2_sata_init_one (struct pci_dev *pdev, const struct pci_device_id *e
 	struct ata_probe_ent *probe_ent = NULL;
 	unsigned long base;
 	void __iomem *mmio_base;
+	const struct k2_board_info *board_info =
+			&k2_board_info[ent->driver_data];
 	int pci_dev_busy = 0;
 	int rc;
 	int i;
@@ -424,7 +451,7 @@ static int k2_sata_init_one (struct pci_dev *pdev, const struct pci_device_id *e
 
 	probe_ent->sht = &k2_sata_sht;
 	probe_ent->port_flags = ATA_FLAG_SATA | ATA_FLAG_NO_LEGACY |
-				ATA_FLAG_MMIO;
+				ATA_FLAG_MMIO | board_info->port_flags;
 	probe_ent->port_ops = &k2_sata_ops;
 	probe_ent->n_ports = 4;
 	probe_ent->irq = pdev->irq;
@@ -441,7 +468,7 @@ static int k2_sata_init_one (struct pci_dev *pdev, const struct pci_device_id *e
 	/* different controllers have different number of ports - currently 4 or 8 */
 	/* All ports are on the same function. Multi-function device is no
 	 * longer available. This should not be seen in any system. */
-	for (i = 0; i < ent->driver_data; i++)
+	for (i = 0; i < board_info->n_ports; i++)
 		k2_sata_setup_port(&probe_ent->port[i], base + i * K2_SATA_PORT_OFFSET);
 
 	pci_set_master(pdev);
@@ -469,11 +496,11 @@ static int k2_sata_init_one (struct pci_dev *pdev, const struct pci_device_id *e
  * controller
  * */
 static const struct pci_device_id k2_sata_pci_tbl[] = {
-	{ PCI_VDEVICE(SERVERWORKS, 0x0240), 4 },
-	{ PCI_VDEVICE(SERVERWORKS, 0x0241), 4 },
-	{ PCI_VDEVICE(SERVERWORKS, 0x0242), 8 },
-	{ PCI_VDEVICE(SERVERWORKS, 0x024a), 4 },
-	{ PCI_VDEVICE(SERVERWORKS, 0x024b), 4 },
+	{ PCI_VDEVICE(SERVERWORKS, 0x0240), board_svw4 },
+	{ PCI_VDEVICE(SERVERWORKS, 0x0241), board_svw4 },
+	{ PCI_VDEVICE(SERVERWORKS, 0x0242), board_svw8 },
+	{ PCI_VDEVICE(SERVERWORKS, 0x024a), board_svw4 },
+	{ PCI_VDEVICE(SERVERWORKS, 0x024b), board_svw4 },
 
 	{ }
 };