via82cxxx: workaround h/w bugs

Add custom struct ide_tp_ops instance to fix the internal bug of some VIA
chipsets which will reset the device register after changing the nIEN bit
in the device control register.

Based on commit bfce5e01 for pata_via host driver.
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ide/via82cxxx.c

@@ -107,6 +107,7 @@ struct via82cxxx_dev
 {
 	struct via_isa_bridge *via_config;
 	unsigned int via_80w;
+	u8 cached_device[2];
 };
 
 /**
@@ -382,10 +383,66 @@ static const struct ide_port_ops via_port_ops = {
 	.cable_detect		= via82cxxx_cable_detect,
 };
 
+static void via_write_devctl(ide_hwif_t *hwif, u8 ctl)
+{
+	struct via82cxxx_dev *vdev = hwif->host->host_priv;
+
+	outb(ctl, hwif->io_ports.ctl_addr);
+	outb(vdev->cached_device[hwif->channel], hwif->io_ports.device_addr);
+}
+
+static void __via_dev_select(ide_drive_t *drive, u8 select)
+{
+	ide_hwif_t *hwif = drive->hwif;
+	struct via82cxxx_dev *vdev = hwif->host->host_priv;
+
+	outb(select, hwif->io_ports.device_addr);
+	vdev->cached_device[hwif->channel] = select;
+}
+
+static void via_dev_select(ide_drive_t *drive)
+{
+	__via_dev_select(drive, drive->select | ATA_DEVICE_OBS);
+}
+
+static void via_tf_load(ide_drive_t *drive, struct ide_taskfile *tf, u8 valid)
+{
+	ide_hwif_t *hwif = drive->hwif;
+	struct ide_io_ports *io_ports = &hwif->io_ports;
+
+	if (valid & IDE_VALID_FEATURE)
+		outb(tf->feature, io_ports->feature_addr);
+	if (valid & IDE_VALID_NSECT)
+		outb(tf->nsect, io_ports->nsect_addr);
+	if (valid & IDE_VALID_LBAL)
+		outb(tf->lbal, io_ports->lbal_addr);
+	if (valid & IDE_VALID_LBAM)
+		outb(tf->lbam, io_ports->lbam_addr);
+	if (valid & IDE_VALID_LBAH)
+		outb(tf->lbah, io_ports->lbah_addr);
+	if (valid & IDE_VALID_DEVICE)
+		__via_dev_select(drive, tf->device);
+}
+
+const struct ide_tp_ops via_tp_ops = {
+	.exec_command		= ide_exec_command,
+	.read_status		= ide_read_status,
+	.read_altstatus		= ide_read_altstatus,
+	.write_devctl		= via_write_devctl,
+
+	.dev_select		= via_dev_select,
+	.tf_load		= via_tf_load,
+	.tf_read		= ide_tf_read,
+
+	.input_data		= ide_input_data,
+	.output_data		= ide_output_data,
+};
+
 static const struct ide_port_info via82cxxx_chipset __devinitdata = {
 	.name		= DRV_NAME,
 	.init_chipset	= init_chipset_via82cxxx,
 	.enablebits	= { { 0x40, 0x02, 0x02 }, { 0x40, 0x01, 0x01 } },
+	.tp_ops		= &via_tp_ops,
 	.port_ops	= &via_port_ops,
 	.host_flags	= IDE_HFLAG_PIO_NO_BLACKLIST |
 			  IDE_HFLAG_POST_SET_MODE |