staging: mt7621-spi: add mt7621 support

NeilBrown:
    The code will fail with a warning if asked to transfer
    more than 32 bytes at a time.  So used max_transfer_size
    interface to tell users about this.

Signed-off-by: John Crispin <blogic@openwrt.org>
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/Kconfig

@@ -122,4 +122,6 @@ source "drivers/staging/mt7621-pinctrl/Kconfig"
 
 source "drivers/staging/mt7621-gpio/Kconfig"
 
+source "drivers/staging/mt7621-spi/Kconfig"
+
 endif # STAGING

drivers/staging/Makefile

@@ -52,3 +52,4 @@ obj-$(CONFIG_PI433)		+= pi433/
 obj-$(CONFIG_SOC_MT7621)	+= mt7621-pci/
 obj-$(CONFIG_SOC_MT7621)	+= mt7621-pinctrl/
 obj-$(CONFIG_SOC_MT7621)	+= mt7621-gpio/
+obj-$(CONFIG_SOC_MT7621)	+= mt7621-spi/

drivers/staging/mt7621-spi/Kconfig

@@ -0,0 +1,6 @@
+config SPI_MT7621
+	tristate "MediaTek MT7621 SPI Controller"
+	depends on RALINK
+	help
+	  This selects a driver for the MediaTek MT7621 SPI Controller.
+

drivers/staging/mt7621-spi/Makefile

@@ -0,0 +1 @@
+obj-$(CONFIG_SPI_MT7621)		+= spi-mt7621.o

drivers/staging/mt7621-spi/TODO

@@ -0,0 +1,5 @@
+
+- general code review and clean up
+- ensure device-tree requirements are documented
+
+Cc: NeilBrown <neil@brown.name>

drivers/staging/mt7621-spi/spi-mt7621.c

@@ -0,0 +1,489 @@
+/*
+ * spi-mt7621.c -- MediaTek MT7621 SPI controller driver
+ *
+ * Copyright (C) 2011 Sergiy <piratfm@gmail.com>
+ * Copyright (C) 2011-2013 Gabor Juhos <juhosg@openwrt.org>
+ * Copyright (C) 2014-2015 Felix Fietkau <nbd@nbd.name>
+ *
+ * Some parts are based on spi-orion.c:
+ *   Author: Shadi Ammouri <shadi@marvell.com>
+ *   Copyright (C) 2007-2008 Marvell Ltd.
+ *
+ * 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.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/reset.h>
+#include <linux/spi/spi.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/swab.h>
+
+#include <ralink_regs.h>
+
+#define SPI_BPW_MASK(bits) BIT((bits) - 1)
+
+#define DRIVER_NAME			"spi-mt7621"
+/* in usec */
+#define RALINK_SPI_WAIT_MAX_LOOP	2000
+
+/* SPISTAT register bit field */
+#define SPISTAT_BUSY			BIT(0)
+
+#define MT7621_SPI_TRANS	0x00
+#define SPITRANS_BUSY		BIT(16)
+
+#define MT7621_SPI_OPCODE	0x04
+#define MT7621_SPI_DATA0	0x08
+#define MT7621_SPI_DATA4	0x18
+#define SPI_CTL_TX_RX_CNT_MASK	0xff
+#define SPI_CTL_START		BIT(8)
+
+#define MT7621_SPI_POLAR	0x38
+#define MT7621_SPI_MASTER	0x28
+#define MT7621_SPI_MOREBUF	0x2c
+#define MT7621_SPI_SPACE	0x3c
+
+#define MT7621_CPHA		BIT(5)
+#define MT7621_CPOL		BIT(4)
+#define MT7621_LSB_FIRST	BIT(3)
+
+#define RT2880_SPI_MODE_BITS	(SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_CS_HIGH)
+
+struct mt7621_spi;
+
+struct mt7621_spi {
+	struct spi_master	*master;
+	void __iomem		*base;
+	unsigned int		sys_freq;
+	unsigned int		speed;
+	struct clk		*clk;
+	spinlock_t		lock;
+
+	struct mt7621_spi_ops	*ops;
+};
+
+static inline struct mt7621_spi *spidev_to_mt7621_spi(struct spi_device *spi)
+{
+	return spi_master_get_devdata(spi->master);
+}
+
+static inline u32 mt7621_spi_read(struct mt7621_spi *rs, u32 reg)
+{
+	return ioread32(rs->base + reg);
+}
+
+static inline void mt7621_spi_write(struct mt7621_spi *rs, u32 reg, u32 val)
+{
+	iowrite32(val, rs->base + reg);
+}
+
+static void mt7621_spi_reset(struct mt7621_spi *rs, int duplex)
+{
+	u32 master = mt7621_spi_read(rs, MT7621_SPI_MASTER);
+
+	master |= 7 << 29;
+	master |= 1 << 2;
+	if (duplex)
+		master |= 1 << 10;
+	else
+		master &= ~(1 << 10);
+
+	mt7621_spi_write(rs, MT7621_SPI_MASTER, master);
+}
+
+static void mt7621_spi_set_cs(struct spi_device *spi, int enable)
+{
+	struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
+	int cs = spi->chip_select;
+	u32 polar = 0;
+
+        mt7621_spi_reset(rs, cs);
+	if (enable)
+		polar = BIT(cs);
+	mt7621_spi_write(rs, MT7621_SPI_POLAR, polar);
+}
+
+static int mt7621_spi_prepare(struct spi_device *spi, unsigned int speed)
+{
+	struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
+	u32 rate;
+	u32 reg;
+
+	dev_dbg(&spi->dev, "speed:%u\n", speed);
+
+	rate = DIV_ROUND_UP(rs->sys_freq, speed);
+	dev_dbg(&spi->dev, "rate-1:%u\n", rate);
+
+	if (rate > 4097)
+		return -EINVAL;
+
+	if (rate < 2)
+		rate = 2;
+
+	reg = mt7621_spi_read(rs, MT7621_SPI_MASTER);
+	reg &= ~(0xfff << 16);
+	reg |= (rate - 2) << 16;
+	rs->speed = speed;
+
+	reg &= ~MT7621_LSB_FIRST;
+	if (spi->mode & SPI_LSB_FIRST)
+		reg |= MT7621_LSB_FIRST;
+
+	reg &= ~(MT7621_CPHA | MT7621_CPOL);
+	switch(spi->mode & (SPI_CPOL | SPI_CPHA)) {
+		case SPI_MODE_0:
+			break;
+		case SPI_MODE_1:
+			reg |= MT7621_CPHA;
+			break;
+		case SPI_MODE_2:
+			reg |= MT7621_CPOL;
+			break;
+		case SPI_MODE_3:
+			reg |= MT7621_CPOL | MT7621_CPHA;
+			break;
+	}
+	mt7621_spi_write(rs, MT7621_SPI_MASTER, reg);
+
+	return 0;
+}
+
+static inline int mt7621_spi_wait_till_ready(struct spi_device *spi)
+{
+	struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
+	int i;
+
+	for (i = 0; i < RALINK_SPI_WAIT_MAX_LOOP; i++) {
+		u32 status;
+
+		status = mt7621_spi_read(rs, MT7621_SPI_TRANS);
+		if ((status & SPITRANS_BUSY) == 0) {
+			return 0;
+		}
+		cpu_relax();
+		udelay(1);
+	}
+
+	return -ETIMEDOUT;
+}
+
+static int mt7621_spi_transfer_half_duplex(struct spi_master *master,
+					   struct spi_message *m)
+{
+	struct mt7621_spi *rs = spi_master_get_devdata(master);
+	struct spi_device *spi = m->spi;
+	unsigned int speed = spi->max_speed_hz;
+	struct spi_transfer *t = NULL;
+	int status = 0;
+	int i, len = 0;
+	int rx_len = 0;
+	u32 data[9] = { 0 };
+	u32 val;
+
+	mt7621_spi_wait_till_ready(spi);
+
+	list_for_each_entry(t, &m->transfers, transfer_list) {
+		const u8 *buf = t->tx_buf;
+
+		if (t->rx_buf)
+			rx_len += t->len;
+
+		if (!buf)
+			continue;
+
+		if (t->speed_hz < speed)
+			speed = t->speed_hz;
+
+		if (WARN_ON(len + t->len > 36)) {
+			status = -EIO;
+			goto msg_done;
+		}
+
+		for (i = 0; i < t->len; i++, len++)
+			data[len / 4] |= buf[i] << (8 * (len & 3));
+	}
+
+	if (WARN_ON(rx_len > 32)) {
+		status = -EIO;
+		goto msg_done;
+	}
+
+	if (mt7621_spi_prepare(spi, speed)) {
+		status = -EIO;
+		goto msg_done;
+	}
+	data[0] = swab32(data[0]);
+	if (len < 4)
+		data[0] >>= (4 - len) * 8;
+
+	for (i = 0; i < len; i += 4)
+		mt7621_spi_write(rs, MT7621_SPI_OPCODE + i, data[i / 4]);
+
+	val = (min_t(int, len, 4) * 8) << 24;
+	if (len > 4)
+		val |= (len - 4) * 8;
+	val |= (rx_len * 8) << 12;
+	mt7621_spi_write(rs, MT7621_SPI_MOREBUF, val);
+
+	mt7621_spi_set_cs(spi, 1);
+
+	val = mt7621_spi_read(rs, MT7621_SPI_TRANS);
+	val |= SPI_CTL_START;
+	mt7621_spi_write(rs, MT7621_SPI_TRANS, val);
+
+	mt7621_spi_wait_till_ready(spi);
+
+	mt7621_spi_set_cs(spi, 0);
+
+	for (i = 0; i < rx_len; i += 4)
+		data[i / 4] = mt7621_spi_read(rs, MT7621_SPI_DATA0 + i);
+
+	m->actual_length = len + rx_len;
+
+	len = 0;
+	list_for_each_entry(t, &m->transfers, transfer_list) {
+		u8 *buf = t->rx_buf;
+
+		if (!buf)
+			continue;
+
+		for (i = 0; i < t->len; i++, len++)
+			buf[i] = data[len / 4] >> (8 * (len & 3));
+	}
+
+msg_done:
+	m->status = status;
+	spi_finalize_current_message(master);
+
+	return 0;
+}
+
+static int mt7621_spi_transfer_full_duplex(struct spi_master *master,
+					   struct spi_message *m)
+{
+	struct mt7621_spi *rs = spi_master_get_devdata(master);
+	struct spi_device *spi = m->spi;
+	unsigned int speed = spi->max_speed_hz;
+	struct spi_transfer *t = NULL;
+	int status = 0;
+	int i, len = 0;
+	int rx_len = 0;
+	u32 data[9] = { 0 };
+	u32 val = 0;
+
+	mt7621_spi_wait_till_ready(spi);
+
+	list_for_each_entry(t, &m->transfers, transfer_list) {
+		const u8 *buf = t->tx_buf;
+
+		if (t->rx_buf)
+			rx_len += t->len;
+
+		if (!buf)
+			continue;
+
+		if (WARN_ON(len + t->len > 16)) {
+			status = -EIO;
+			goto msg_done;
+		}
+
+		for (i = 0; i < t->len; i++, len++)
+			data[len / 4] |= buf[i] << (8 * (len & 3));
+		if (speed > t->speed_hz)
+			speed = t->speed_hz;
+	}
+
+	if (WARN_ON(rx_len > 16)) {
+		status = -EIO;
+		goto msg_done;
+	}
+
+	if (mt7621_spi_prepare(spi, speed)) {
+		status = -EIO;
+		goto msg_done;
+	}
+
+	for (i = 0; i < len; i += 4)
+		mt7621_spi_write(rs, MT7621_SPI_DATA0 + i, data[i / 4]);
+
+	val |= len * 8;
+	val |= (rx_len * 8) << 12;
+	mt7621_spi_write(rs, MT7621_SPI_MOREBUF, val);
+
+	mt7621_spi_set_cs(spi, 1);
+
+	val = mt7621_spi_read(rs, MT7621_SPI_TRANS);
+	val |= SPI_CTL_START;
+	mt7621_spi_write(rs, MT7621_SPI_TRANS, val);
+
+	mt7621_spi_wait_till_ready(spi);
+
+	mt7621_spi_set_cs(spi, 0);
+
+	for (i = 0; i < rx_len; i += 4)
+		data[i / 4] = mt7621_spi_read(rs, MT7621_SPI_DATA4 + i);
+
+	m->actual_length = rx_len;
+
+	len = 0;
+	list_for_each_entry(t, &m->transfers, transfer_list) {
+		u8 *buf = t->rx_buf;
+
+		if (!buf)
+			continue;
+
+		for (i = 0; i < t->len; i++, len++)
+			buf[i] = data[len / 4] >> (8 * (len & 3));
+	}
+
+msg_done:
+	m->status = status;
+	spi_finalize_current_message(master);
+
+	return 0;
+}
+
+static int mt7621_spi_transfer_one_message(struct spi_master *master,
+					   struct spi_message *m)
+{
+	struct spi_device *spi = m->spi;
+	int cs = spi->chip_select;
+
+	if (cs)
+		return mt7621_spi_transfer_full_duplex(master, m);
+	return mt7621_spi_transfer_half_duplex(master, m);
+}
+
+static int mt7621_spi_setup(struct spi_device *spi)
+{
+	struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
+
+	if ((spi->max_speed_hz == 0) ||
+		(spi->max_speed_hz > (rs->sys_freq / 2)))
+		spi->max_speed_hz = (rs->sys_freq / 2);
+
+	if (spi->max_speed_hz < (rs->sys_freq / 4097)) {
+		dev_err(&spi->dev, "setup: requested speed is too low %d Hz\n",
+			spi->max_speed_hz);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id mt7621_spi_match[] = {
+	{ .compatible = "ralink,mt7621-spi" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mt7621_spi_match);
+
+static size_t max_transfer_size(struct spi_device *spi)
+{
+	return 32;
+}
+
+static int mt7621_spi_probe(struct platform_device *pdev)
+{
+	const struct of_device_id *match;
+	struct spi_master *master;
+	struct mt7621_spi *rs;
+	unsigned long flags;
+	void __iomem *base;
+	struct resource *r;
+	int status = 0;
+	struct clk *clk;
+	struct mt7621_spi_ops *ops;
+
+	match = of_match_device(mt7621_spi_match, &pdev->dev);
+	if (!match)
+		return -EINVAL;
+	ops = (struct mt7621_spi_ops *)match->data;
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	base = devm_ioremap_resource(&pdev->dev, r);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(clk)) {
+		dev_err(&pdev->dev, "unable to get SYS clock, err=%d\n",
+			status);
+		return PTR_ERR(clk);
+	}
+
+	status = clk_prepare_enable(clk);
+	if (status)
+		return status;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*rs));
+	if (master == NULL) {
+		dev_info(&pdev->dev, "master allocation failed\n");
+		return -ENOMEM;
+	}
+
+	master->mode_bits = RT2880_SPI_MODE_BITS;
+
+	master->setup = mt7621_spi_setup;
+	master->transfer_one_message = mt7621_spi_transfer_one_message;
+	master->bits_per_word_mask = SPI_BPW_MASK(8);
+	master->dev.of_node = pdev->dev.of_node;
+	master->num_chipselect = 2;
+	master->max_transfer_size = max_transfer_size;
+
+	dev_set_drvdata(&pdev->dev, master);
+
+	rs = spi_master_get_devdata(master);
+	rs->base = base;
+	rs->clk = clk;
+	rs->master = master;
+	rs->sys_freq = clk_get_rate(rs->clk);
+	rs->ops = ops;
+	dev_info(&pdev->dev, "sys_freq: %u\n", rs->sys_freq);
+	spin_lock_irqsave(&rs->lock, flags);
+
+	device_reset(&pdev->dev);
+
+	mt7621_spi_reset(rs, 0);
+
+	return spi_register_master(master);
+}
+
+static int mt7621_spi_remove(struct platform_device *pdev)
+{
+	struct spi_master *master;
+	struct mt7621_spi *rs;
+
+	master = dev_get_drvdata(&pdev->dev);
+	rs = spi_master_get_devdata(master);
+
+	clk_disable(rs->clk);
+	spi_unregister_master(master);
+
+	return 0;
+}
+
+MODULE_ALIAS("platform:" DRIVER_NAME);
+
+static struct platform_driver mt7621_spi_driver = {
+	.driver = {
+		.name = DRIVER_NAME,
+		.owner = THIS_MODULE,
+		.of_match_table = mt7621_spi_match,
+	},
+	.probe = mt7621_spi_probe,
+	.remove = mt7621_spi_remove,
+};
+
+module_platform_driver(mt7621_spi_driver);
+
+MODULE_DESCRIPTION("MT7621 SPI driver");
+MODULE_AUTHOR("Felix Fietkau <nbd@nbd.name>");
+MODULE_LICENSE("GPL");