ata: pata_of_platform: Allow to use 16-bit wide data transfer

In some cases, the system bus can be configured for 16-bit mode,
in this case using read/write functions for 32-bit values
results in two cycles of 16 bits each, which is wrong.
This patch adds the devicetree flag to switch the driver to
use 16-bit mode for I/O transfers.

Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/ata/pata_of_platform.c

@@ -32,6 +32,7 @@ static int pata_of_platform_probe(struct platform_device *ofdev)
 	unsigned int reg_shift = 0;
 	int pio_mode = 0;
 	int pio_mask;
+	bool use16bit;
 
 	ret = of_address_to_resource(dn, 0, &io_res);
 	if (ret) {
@@ -60,11 +61,14 @@ static int pata_of_platform_probe(struct platform_device *ofdev)
 		dev_info(&ofdev->dev, "pio-mode unspecified, assuming PIO0\n");
 	}
 
+	use16bit = of_property_read_bool(dn, "ata-generic,use16bit");
+
 	pio_mask = 1 << pio_mode;
 	pio_mask |= (1 << pio_mode) - 1;
 
 	return __pata_platform_probe(&ofdev->dev, &io_res, &ctl_res, irq_res,
-				     reg_shift, pio_mask, &pata_platform_sht);
+				     reg_shift, pio_mask, &pata_platform_sht,
+				     use16bit);
 }
 
 static const struct of_device_id pata_of_platform_match[] = {

drivers/ata/pata_platform.c

@@ -47,13 +47,6 @@ static struct scsi_host_template pata_platform_sht = {
 	ATA_PIO_SHT(DRV_NAME),
 };
 
-static struct ata_port_operations pata_platform_port_ops = {
-	.inherits		= &ata_sff_port_ops,
-	.sff_data_xfer		= ata_sff_data_xfer32,
-	.cable_detect		= ata_cable_unknown,
-	.set_mode		= pata_platform_set_mode,
-};
-
 static void pata_platform_setup_port(struct ata_ioports *ioaddr,
 				     unsigned int shift)
 {
@@ -79,6 +72,7 @@ static void pata_platform_setup_port(struct ata_ioports *ioaddr,
  *	@ioport_shift: I/O port shift
  *	@__pio_mask: PIO mask
  *	@sht: scsi_host_template to use when registering
+ *	@use16bit: Flag to indicate 16-bit IO instead of 32-bit
  *
  *	Register a platform bus IDE interface. Such interfaces are PIO and we
  *	assume do not support IRQ sharing.
@@ -101,7 +95,7 @@ static void pata_platform_setup_port(struct ata_ioports *ioaddr,
 int __pata_platform_probe(struct device *dev, struct resource *io_res,
 			  struct resource *ctl_res, struct resource *irq_res,
 			  unsigned int ioport_shift, int __pio_mask,
-			  struct scsi_host_template *sht)
+			  struct scsi_host_template *sht, bool use16bit)
 {
 	struct ata_host *host;
 	struct ata_port *ap;
@@ -131,7 +125,15 @@ int __pata_platform_probe(struct device *dev, struct resource *io_res,
 		return -ENOMEM;
 	ap = host->ports[0];
 
-	ap->ops = &pata_platform_port_ops;
+	ap->ops = devm_kzalloc(dev, sizeof(*ap->ops), GFP_KERNEL);
+	ap->ops->inherits = &ata_sff_port_ops;
+	ap->ops->cable_detect = ata_cable_unknown;
+	ap->ops->set_mode = pata_platform_set_mode;
+	if (use16bit)
+		ap->ops->sff_data_xfer = ata_sff_data_xfer;
+	else
+		ap->ops->sff_data_xfer = ata_sff_data_xfer32;
+
 	ap->pio_mask = __pio_mask;
 	ap->flags |= ATA_FLAG_SLAVE_POSS;
 
@@ -218,7 +220,7 @@ static int pata_platform_probe(struct platform_device *pdev)
 
 	return __pata_platform_probe(&pdev->dev, io_res, ctl_res, irq_res,
 				     pp_info ? pp_info->ioport_shift : 0,
-				     pio_mask, &pata_platform_sht);
+				     pio_mask, &pata_platform_sht, false);
 }
 
 static struct platform_driver pata_platform_driver = {

include/linux/ata_platform.h

@@ -19,7 +19,8 @@ extern int __pata_platform_probe(struct device *dev,
 				 struct resource *irq_res,
 				 unsigned int ioport_shift,
 				 int __pio_mask,
-				 struct scsi_host_template *sht);
+				 struct scsi_host_template *sht,
+				 bool use16bit);
 
 /*
  * Marvell SATA private data