SPI: MIPS: lantiq: add FALCON spi driver

The external bus unit (EBU) found on the FALCON SoC has spi emulation that is
designed for serial flash access. This driver has only been tested with m25p80
type chips. The hardware has no support for other types of spi peripherals.

Signed-off-by: Thomas Langer <thomas.langer@lantiq.com>
Signed-off-by: John Crispin <blogic@openwrt.org>
Cc: spi-devel-general@lists.sourceforge.net
Cc: linux-mips@linux-mips.org
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Patchwork: https://patchwork.linux-mips.org/patch/3844/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 479 insertions, 0 deletions

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index cd2fe350e724..b18abf31fd08 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -144,6 +144,15 @@ config SPI_EP93XX
 	  This enables using the Cirrus EP93xx SPI controller in master
 	  mode.
 
+config SPI_FALCON
+	tristate "Falcon SPI controller support"
+	depends on SOC_FALCON
+	help
+	  The external bus unit (EBU) found on the FALC-ON SoC has SPI
+	  emulation that is designed for serial flash access. This driver
+	  has only been tested with m25p80 type chips. The hardware has no
+	  support for other types of SPI peripherals.
+
 config SPI_GPIO
 	tristate "GPIO-based bitbanging SPI Master"
 	depends on GENERIC_GPIO
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 9d75d2198ff5..b5cbab2b5ab0 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -26,6 +26,7 @@ obj-$(CONFIG_SPI_DW_MMIO)		+= spi-dw-mmio.o
 obj-$(CONFIG_SPI_DW_PCI)		+= spi-dw-midpci.o
 spi-dw-midpci-objs			:= spi-dw-pci.o spi-dw-mid.o
 obj-$(CONFIG_SPI_EP93XX)		+= spi-ep93xx.o
+obj-$(CONFIG_SPI_FALCON)		+= spi-falcon.o
 obj-$(CONFIG_SPI_FSL_LIB)		+= spi-fsl-lib.o
 obj-$(CONFIG_SPI_FSL_ESPI)		+= spi-fsl-espi.o
 obj-$(CONFIG_SPI_FSL_SPI)		+= spi-fsl-spi.o
diff --git a/drivers/spi/spi-falcon.c b/drivers/spi/spi-falcon.c
new file mode 100644
index 000000000000..8f6aa735a24c
--- /dev/null
+++ b/drivers/spi/spi-falcon.c
@@ -0,0 +1,469 @@
+/*
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ *
+ *  Copyright (C) 2012 Thomas Langer <thomas.langer@lantiq.com>
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/spi/spi.h>
+#include <linux/delay.h>
+#include <linux/workqueue.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+
+#include <lantiq_soc.h>
+
+#define DRV_NAME		"sflash-falcon"
+
+#define FALCON_SPI_XFER_BEGIN	(1 << 0)
+#define FALCON_SPI_XFER_END	(1 << 1)
+
+/* Bus Read Configuration Register0 */
+#define BUSRCON0		0x00000010
+/* Bus Write Configuration Register0 */
+#define BUSWCON0		0x00000018
+/* Serial Flash Configuration Register */
+#define SFCON			0x00000080
+/* Serial Flash Time Register */
+#define SFTIME			0x00000084
+/* Serial Flash Status Register */
+#define SFSTAT			0x00000088
+/* Serial Flash Command Register */
+#define SFCMD			0x0000008C
+/* Serial Flash Address Register */
+#define SFADDR			0x00000090
+/* Serial Flash Data Register */
+#define SFDATA			0x00000094
+/* Serial Flash I/O Control Register */
+#define SFIO			0x00000098
+/* EBU Clock Control Register */
+#define EBUCC			0x000000C4
+
+/* Dummy Phase Length */
+#define SFCMD_DUMLEN_OFFSET	16
+#define SFCMD_DUMLEN_MASK	0x000F0000
+/* Chip Select */
+#define SFCMD_CS_OFFSET		24
+#define SFCMD_CS_MASK		0x07000000
+/* field offset */
+#define SFCMD_ALEN_OFFSET	20
+#define SFCMD_ALEN_MASK		0x00700000
+/* SCK Rise-edge Position */
+#define SFTIME_SCKR_POS_OFFSET	8
+#define SFTIME_SCKR_POS_MASK	0x00000F00
+/* SCK Period */
+#define SFTIME_SCK_PER_OFFSET	0
+#define SFTIME_SCK_PER_MASK	0x0000000F
+/* SCK Fall-edge Position */
+#define SFTIME_SCKF_POS_OFFSET	12
+#define SFTIME_SCKF_POS_MASK	0x0000F000
+/* Device Size */
+#define SFCON_DEV_SIZE_A23_0	0x03000000
+#define SFCON_DEV_SIZE_MASK	0x0F000000
+/* Read Data Position */
+#define SFTIME_RD_POS_MASK	0x000F0000
+/* Data Output */
+#define SFIO_UNUSED_WD_MASK	0x0000000F
+/* Command Opcode mask */
+#define SFCMD_OPC_MASK		0x000000FF
+/* dlen bytes of data to write */
+#define SFCMD_DIR_WRITE		0x00000100
+/* Data Length offset */
+#define SFCMD_DLEN_OFFSET	9
+/* Command Error */
+#define SFSTAT_CMD_ERR		0x20000000
+/* Access Command Pending */
+#define SFSTAT_CMD_PEND		0x00400000
+/* Frequency set to 100MHz. */
+#define EBUCC_EBUDIV_SELF100	0x00000001
+/* Serial Flash */
+#define BUSRCON0_AGEN_SERIAL_FLASH	0xF0000000
+/* 8-bit multiplexed */
+#define BUSRCON0_PORTW_8_BIT_MUX	0x00000000
+/* Serial Flash */
+#define BUSWCON0_AGEN_SERIAL_FLASH	0xF0000000
+/* Chip Select after opcode */
+#define SFCMD_KEEP_CS_KEEP_SELECTED	0x00008000
+
+#define CLOCK_100M	100000000
+#define CLOCK_50M	50000000
+
+struct falcon_sflash {
+	u32 sfcmd; /* for caching of opcode, direction, ... */
+	struct spi_master *master;
+};
+
+int falcon_sflash_xfer(struct spi_device *spi, struct spi_transfer *t,
+		unsigned long flags)
+{
+	struct device *dev = &spi->dev;
+	struct falcon_sflash *priv = spi_master_get_devdata(spi->master);
+	const u8 *txp = t->tx_buf;
+	u8 *rxp = t->rx_buf;
+	unsigned int bytelen = ((8 * t->len + 7) / 8);
+	unsigned int len, alen, dumlen;
+	u32 val;
+	enum {
+		state_init,
+		state_command_prepare,
+		state_write,
+		state_read,
+		state_disable_cs,
+		state_end
+	} state = state_init;
+
+	do {
+		switch (state) {
+		case state_init: /* detect phase of upper layer sequence */
+		{
+			/* initial write ? */
+			if (flags & FALCON_SPI_XFER_BEGIN) {
+				if (!txp) {
+					dev_err(dev,
+						"BEGIN without tx data!\n");
+					return -ENODATA;
+				}
+				/*
+				 * Prepare the parts of the sfcmd register,
+				 * which should not change during a sequence!
+				 * Only exception are the length fields,
+				 * especially alen and dumlen.
+				 */
+
+				priv->sfcmd = ((spi->chip_select
+						<< SFCMD_CS_OFFSET)
+					       & SFCMD_CS_MASK);
+				priv->sfcmd |= SFCMD_KEEP_CS_KEEP_SELECTED;
+				priv->sfcmd |= *txp;
+				txp++;
+				bytelen--;
+				if (bytelen) {
+					/*
+					 * more data:
+					 * maybe address and/or dummy
+					 */
+					state = state_command_prepare;
+					break;
+				} else {
+					dev_dbg(dev, "write cmd %02X\n",
+						priv->sfcmd & SFCMD_OPC_MASK);
+				}
+			}
+			/* continued write ? */
+			if (txp && bytelen) {
+				state = state_write;
+				break;
+			}
+			/* read data? */
+			if (rxp && bytelen) {
+				state = state_read;
+				break;
+			}
+			/* end of sequence? */
+			if (flags & FALCON_SPI_XFER_END)
+				state = state_disable_cs;
+			else
+				state = state_end;
+			break;
+		}
+		/* collect tx data for address and dummy phase */
+		case state_command_prepare:
+		{
+			/* txp is valid, already checked */
+			val = 0;
+			alen = 0;
+			dumlen = 0;
+			while (bytelen > 0) {
+				if (alen < 3) {
+					val = (val << 8) | (*txp++);
+					alen++;
+				} else if ((dumlen < 15) && (*txp == 0)) {
+					/*
+					 * assume dummy bytes are set to 0
+					 * from upper layer
+					 */
+					dumlen++;
+					txp++;
+				} else {
+					break;
+				}
+				bytelen--;
+			}
+			priv->sfcmd &= ~(SFCMD_ALEN_MASK | SFCMD_DUMLEN_MASK);
+			priv->sfcmd |= (alen << SFCMD_ALEN_OFFSET) |
+					 (dumlen << SFCMD_DUMLEN_OFFSET);
+			if (alen > 0)
+				ltq_ebu_w32(val, SFADDR);
+
+			dev_dbg(dev, "wr %02X, alen=%d (addr=%06X) dlen=%d\n",
+				priv->sfcmd & SFCMD_OPC_MASK,
+				alen, val, dumlen);
+
+			if (bytelen > 0) {
+				/* continue with write */
+				state = state_write;
+			} else if (flags & FALCON_SPI_XFER_END) {
+				/* end of sequence? */
+				state = state_disable_cs;
+			} else {
+				/*
+				 * go to end and expect another
+				 * call (read or write)
+				 */
+				state = state_end;
+			}
+			break;
+		}
+		case state_write:
+		{
+			/* txp still valid */
+			priv->sfcmd |= SFCMD_DIR_WRITE;
+			len = 0;
+			val = 0;
+			do {
+				if (bytelen--)
+					val |= (*txp++) << (8 * len++);
+				if ((flags & FALCON_SPI_XFER_END)
+				    && (bytelen == 0)) {
+					priv->sfcmd &=
+						~SFCMD_KEEP_CS_KEEP_SELECTED;
+				}
+				if ((len == 4) || (bytelen == 0)) {
+					ltq_ebu_w32(val, SFDATA);
+					ltq_ebu_w32(priv->sfcmd
+						| (len<<SFCMD_DLEN_OFFSET),
+						SFCMD);
+					len = 0;
+					val = 0;
+					priv->sfcmd &= ~(SFCMD_ALEN_MASK
+							 | SFCMD_DUMLEN_MASK);
+				}
+			} while (bytelen);
+			state = state_end;
+			break;
+		}
+		case state_read:
+		{
+			/* read data */
+			priv->sfcmd &= ~SFCMD_DIR_WRITE;
+			do {
+				if ((flags & FALCON_SPI_XFER_END)
+				    && (bytelen <= 4)) {
+					priv->sfcmd &=
+						~SFCMD_KEEP_CS_KEEP_SELECTED;
+				}
+				len = (bytelen > 4) ? 4 : bytelen;
+				bytelen -= len;
+				ltq_ebu_w32(priv->sfcmd
+					| (len << SFCMD_DLEN_OFFSET), SFCMD);
+				priv->sfcmd &= ~(SFCMD_ALEN_MASK
+						 | SFCMD_DUMLEN_MASK);
+				do {
+					val = ltq_ebu_r32(SFSTAT);
+					if (val & SFSTAT_CMD_ERR) {
+						/* reset error status */
+						dev_err(dev, "SFSTAT: CMD_ERR");
+						dev_err(dev, " (%x)\n", val);
+						ltq_ebu_w32(SFSTAT_CMD_ERR,
+							SFSTAT);
+						return -EBADE;
+					}
+				} while (val & SFSTAT_CMD_PEND);
+				val = ltq_ebu_r32(SFDATA);
+				do {
+					*rxp = (val & 0xFF);
+					rxp++;
+					val >>= 8;
+					len--;
+				} while (len);
+			} while (bytelen);
+			state = state_end;
+			break;
+		}
+		case state_disable_cs:
+		{
+			priv->sfcmd &= ~SFCMD_KEEP_CS_KEEP_SELECTED;
+			ltq_ebu_w32(priv->sfcmd | (0 << SFCMD_DLEN_OFFSET),
+				SFCMD);
+			val = ltq_ebu_r32(SFSTAT);
+			if (val & SFSTAT_CMD_ERR) {
+				/* reset error status */
+				dev_err(dev, "SFSTAT: CMD_ERR (%x)\n", val);
+				ltq_ebu_w32(SFSTAT_CMD_ERR, SFSTAT);
+				return -EBADE;
+			}
+			state = state_end;
+			break;
+		}
+		case state_end:
+			break;
+		}
+	} while (state != state_end);
+
+	return 0;
+}
+
+static int falcon_sflash_setup(struct spi_device *spi)
+{
+	unsigned int i;
+	unsigned long flags;
+
+	if (spi->chip_select > 0)
+		return -ENODEV;
+
+	spin_lock_irqsave(&ebu_lock, flags);
+
+	if (spi->max_speed_hz >= CLOCK_100M) {
+		/* set EBU clock to 100 MHz */
+		ltq_sys1_w32_mask(0, EBUCC_EBUDIV_SELF100, EBUCC);
+		i = 1; /* divider */
+	} else {
+		/* set EBU clock to 50 MHz */
+		ltq_sys1_w32_mask(EBUCC_EBUDIV_SELF100, 0, EBUCC);
+
+		/* search for suitable divider */
+		for (i = 1; i < 7; i++) {
+			if (CLOCK_50M / i <= spi->max_speed_hz)
+				break;
+		}
+	}
+
+	/* setup period of serial clock */
+	ltq_ebu_w32_mask(SFTIME_SCKF_POS_MASK
+		     | SFTIME_SCKR_POS_MASK
+		     | SFTIME_SCK_PER_MASK,
+		     (i << SFTIME_SCKR_POS_OFFSET)
+		     | (i << (SFTIME_SCK_PER_OFFSET + 1)),
+		     SFTIME);
+
+	/*
+	 * set some bits of unused_wd, to not trigger HOLD/WP
+	 * signals on non QUAD flashes
+	 */
+	ltq_ebu_w32((SFIO_UNUSED_WD_MASK & (0x8 | 0x4)), SFIO);
+
+	ltq_ebu_w32(BUSRCON0_AGEN_SERIAL_FLASH | BUSRCON0_PORTW_8_BIT_MUX,
+			BUSRCON0);
+	ltq_ebu_w32(BUSWCON0_AGEN_SERIAL_FLASH, BUSWCON0);
+	/* set address wrap around to maximum for 24-bit addresses */
+	ltq_ebu_w32_mask(SFCON_DEV_SIZE_MASK, SFCON_DEV_SIZE_A23_0, SFCON);
+
+	spin_unlock_irqrestore(&ebu_lock, flags);
+
+	return 0;
+}
+
+static int falcon_sflash_prepare_xfer(struct spi_master *master)
+{
+	return 0;
+}
+
+static int falcon_sflash_unprepare_xfer(struct spi_master *master)
+{
+	return 0;
+}
+
+static int falcon_sflash_xfer_one(struct spi_master *master,
+					struct spi_message *m)
+{
+	struct falcon_sflash *priv = spi_master_get_devdata(master);
+	struct spi_transfer *t;
+	unsigned long spi_flags;
+	unsigned long flags;
+	int ret = 0;
+
+	priv->sfcmd = 0;
+	m->actual_length = 0;
+
+	spi_flags = FALCON_SPI_XFER_BEGIN;
+	list_for_each_entry(t, &m->transfers, transfer_list) {
+		if (list_is_last(&t->transfer_list, &m->transfers))
+			spi_flags |= FALCON_SPI_XFER_END;
+
+		spin_lock_irqsave(&ebu_lock, flags);
+		ret = falcon_sflash_xfer(m->spi, t, spi_flags);
+		spin_unlock_irqrestore(&ebu_lock, flags);
+
+		if (ret)
+			break;
+
+		m->actual_length += t->len;
+
+		WARN_ON(t->delay_usecs || t->cs_change);
+		spi_flags = 0;
+	}
+
+	m->status = ret;
+	m->complete(m->context);
+
+	return 0;
+}
+
+static int __devinit falcon_sflash_probe(struct platform_device *pdev)
+{
+	struct falcon_sflash *priv;
+	struct spi_master *master;
+	int ret;
+
+	if (ltq_boot_select() != BS_SPI) {
+		dev_err(&pdev->dev, "invalid bootstrap options\n");
+		return -ENODEV;
+	}
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*priv));
+	if (!master)
+		return -ENOMEM;
+
+	priv = spi_master_get_devdata(master);
+	priv->master = master;
+
+	master->mode_bits = SPI_MODE_3;
+	master->num_chipselect = 1;
+	master->bus_num = -1;
+	master->setup = falcon_sflash_setup;
+	master->prepare_transfer_hardware = falcon_sflash_prepare_xfer;
+	master->transfer_one_message = falcon_sflash_xfer_one;
+	master->unprepare_transfer_hardware = falcon_sflash_unprepare_xfer;
+	master->dev.of_node = pdev->dev.of_node;
+
+	platform_set_drvdata(pdev, priv);
+
+	ret = spi_register_master(master);
+	if (ret)
+		spi_master_put(master);
+	return ret;
+}
+
+static int __devexit falcon_sflash_remove(struct platform_device *pdev)
+{
+	struct falcon_sflash *priv = platform_get_drvdata(pdev);
+
+	spi_unregister_master(priv->master);
+
+	return 0;
+}
+
+static const struct of_device_id falcon_sflash_match[] = {
+	{ .compatible = "lantiq,sflash-falcon" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, falcon_sflash_match);
+
+static struct platform_driver falcon_sflash_driver = {
+	.probe	= falcon_sflash_probe,
+	.remove	= __devexit_p(falcon_sflash_remove),
+	.driver = {
+		.name	= DRV_NAME,
+		.owner	= THIS_MODULE,
+		.of_match_table = falcon_sflash_match,
+	}
+};
+
+module_platform_driver(falcon_sflash_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Lantiq Falcon SPI/SFLASH controller driver");