[RFC] serial: ns16550: Set read/write functions depending on reg-io-width

[Wadim Egorov]

Set proper register read/write functions depending on reg-io-width
device tree property.

Signed-off-by: Wadim Egorov <w.egorov at phytec.de>
---

of_platform_device_create() creates resources in the device_d struct.
ns16550_init_iomem() and ns16550_init_ioport() are reading the resources
and it's flags (register width).
So both functions are not failing, because there is a valid resource.
The res->flags might be not set at all. And if it is not set, the driver
will use always IORESOURCE_MEM_8BIT.

With this patch the probe_dt() func will override the read/write funcs,
if there is a valid reg-io-width property.
---
 drivers/serial/serial_ns16550.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/serial/serial_ns16550.c b/drivers/serial/serial_ns16550.c
index c6548e3..752e77b 100644
--- a/drivers/serial/serial_ns16550.c
+++ b/drivers/serial/serial_ns16550.c
@@ -287,12 +287,31 @@ static int ns16550_tstc(struct console_device *cdev)
 static void ns16550_probe_dt(struct device_d *dev, struct ns16550_priv *priv)
 {
 	struct device_node *np = dev->device_node;
+	u32 width;
 
 	if (!IS_ENABLED(CONFIG_OFDEVICE))
 		return;
 
 	of_property_read_u32(np, "clock-frequency", &priv->plat.clock);
 	of_property_read_u32(np, "reg-shift", &priv->plat.shift);
+	if (!of_property_read_u32(np, "reg-io-width", &width))
+		switch (width) {
+		case 1:
+			priv->read_reg = ns16550_read_reg_mmio_8;
+			priv->write_reg = ns16550_write_reg_mmio_8;
+			break;
+		case 2:
+			priv->read_reg = ns16550_read_reg_mmio_16;
+			priv->write_reg = ns16550_write_reg_mmio_16;
+			break;
+		case 4:
+			priv->read_reg = ns16550_read_reg_mmio_32;
+			priv->write_reg = ns16550_write_reg_mmio_32;
+			break;
+		default:
+			dev_err(dev, "unsupported reg-io-width (%d)\n",
+				width);
+		}
 }
 
 static struct ns16550_drvdata ns16450_drvdata = {
-- 
1.9.1