net: w5100: support SPI interface mode

This adds new w5100-spi driver which shares the bus interface
independent code with existing w5100 driver.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Mike Sinkovsky <msink@permonline.ru>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/wiznet/Kconfig

@@ -69,4 +69,18 @@ config WIZNET_BUS_ANY
 	  Performance may decrease compared to explicitly selected bus mode.
 endchoice
 
+config WIZNET_W5100_SPI
+	tristate "WIZnet W5100 Ethernet support for SPI mode"
+	depends on WIZNET_BUS_ANY
+	depends on SPI
+	---help---
+	  In SPI mode host system accesses registers using SPI protocol
+	  (mode 0) on the SPI bus.
+
+	  Performance decreases compared to other bus interface mode.
+	  In W5100 SPI mode, burst READ/WRITE processing are not provided.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called w5100-spi.
+
 endif # NET_VENDOR_WIZNET

drivers/net/ethernet/wiznet/Makefile

 obj-$(CONFIG_WIZNET_W5100) += w5100.o
+obj-$(CONFIG_WIZNET_W5100_SPI) += w5100-spi.o
 obj-$(CONFIG_WIZNET_W5300) += w5300.o

drivers/net/ethernet/wiznet/w5100-spi.c

+/*
+ * Ethernet driver for the WIZnet W5100 chip.
+ *
+ * Copyright (C) 2016 Akinobu Mita <akinobu.mita@gmail.com>
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/netdevice.h>
+#include <linux/spi/spi.h>
+
+#include "w5100.h"
+
+#define W5100_SPI_WRITE_OPCODE 0xf0
+#define W5100_SPI_READ_OPCODE 0x0f
+
+static int w5100_spi_read(struct net_device *ndev, u16 addr)
+{
+	struct spi_device *spi = to_spi_device(ndev->dev.parent);
+	u8 cmd[3] = { W5100_SPI_READ_OPCODE, addr >> 8, addr & 0xff };
+	u8 data;
+	int ret;
+
+	ret = spi_write_then_read(spi, cmd, sizeof(cmd), &data, 1);
+
+	return ret ? ret : data;
+}
+
+static int w5100_spi_write(struct net_device *ndev, u16 addr, u8 data)
+{
+	struct spi_device *spi = to_spi_device(ndev->dev.parent);
+	u8 cmd[4] = { W5100_SPI_WRITE_OPCODE, addr >> 8, addr & 0xff, data};
+
+	return spi_write_then_read(spi, cmd, sizeof(cmd), NULL, 0);
+}
+
+static int w5100_spi_read16(struct net_device *ndev, u16 addr)
+{
+	u16 data;
+	int ret;
+
+	ret = w5100_spi_read(ndev, addr);
+	if (ret < 0)
+		return ret;
+	data = ret << 8;
+	ret = w5100_spi_read(ndev, addr + 1);
+
+	return ret < 0 ? ret : data | ret;
+}
+
+static int w5100_spi_write16(struct net_device *ndev, u16 addr, u16 data)
+{
+	int ret;
+
+	ret = w5100_spi_write(ndev, addr, data >> 8);
+	if (ret)
+		return ret;
+
+	return w5100_spi_write(ndev, addr + 1, data & 0xff);
+}
+
+static int w5100_spi_readbulk(struct net_device *ndev, u16 addr, u8 *buf,
+			      int len)
+{
+	int i;
+
+	for (i = 0; i < len; i++) {
+		int ret = w5100_spi_read(ndev, addr + i);
+
+		if (ret < 0)
+			return ret;
+		buf[i] = ret;
+	}
+
+	return 0;
+}
+
+static int w5100_spi_writebulk(struct net_device *ndev, u16 addr, const u8 *buf,
+			       int len)
+{
+	int i;
+
+	for (i = 0; i < len; i++) {
+		int ret = w5100_spi_write(ndev, addr + i, buf[i]);
+
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static const struct w5100_ops w5100_spi_ops = {
+	.may_sleep = true,
+	.read = w5100_spi_read,
+	.write = w5100_spi_write,
+	.read16 = w5100_spi_read16,
+	.write16 = w5100_spi_write16,
+	.readbulk = w5100_spi_readbulk,
+	.writebulk = w5100_spi_writebulk,
+};
+
+static int w5100_spi_probe(struct spi_device *spi)
+{
+	return w5100_probe(&spi->dev, &w5100_spi_ops, 0, NULL, spi->irq,
+			   -EINVAL);
+}
+
+static int w5100_spi_remove(struct spi_device *spi)
+{
+	return w5100_remove(&spi->dev);
+}
+
+static const struct spi_device_id w5100_spi_ids[] = {
+	{ "w5100", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, w5100_spi_ids);
+
+static struct spi_driver w5100_spi_driver = {
+	.driver		= {
+		.name	= "w5100",
+		.pm	= &w5100_pm_ops,
+	},
+	.probe		= w5100_spi_probe,
+	.remove		= w5100_spi_remove,
+	.id_table	= w5100_spi_ids,
+};
+module_spi_driver(w5100_spi_driver);
+
+MODULE_DESCRIPTION("WIZnet W5100 Ethernet driver for SPI mode");
+MODULE_AUTHOR("Akinobu Mita <akinobu.mita@gmail.com>");
+MODULE_LICENSE("GPL");