spi: Add SPI driver for MT76xx SoCs

This patch adds the SPI driver for the MediaTek MT7688 SoC (and
derivates). Its been tested on the LinkIt Smart 7688 and the Gardena
Smart Gateway with and SPI NOR on CS0 and on the Gardena Smart
Gateway additionally with an SPI NAND on CS1.

Note that the SPI controller only supports a max transfer size of 32
bytes. This driver implementes a workaround to enable bigger xfer
sizes to speed up the transfer especially for the SPI NAND support.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Jagan Teki <jagan@openedev.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Cc: Piotr Dymacz <pepe2k@gmail.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

drivers/spi/Kconfig

@@ -116,6 +116,14 @@ config ICH_SPI
 	  access the SPI NOR flash on platforms embedding this Intel
 	  ICH IP core.
 
+config MT7621_SPI
+	bool "MediaTek MT7621 SPI driver"
+	depends on ARCH_MT7620
+	help
+	  Enable the MT7621 SPI driver. This driver can be used to access
+	  the SPI NOR flash on platforms embedding this Ralink / MediaTek
+	  SPI core, like MT7621/7628/7688.
+
 config MVEBU_A3700_SPI
 	bool "Marvell Armada 3700 SPI driver"
 	select CLK_ARMADA_3720

drivers/spi/Makefile

@@ -33,6 +33,7 @@ obj-$(CONFIG_KIRKWOOD_SPI) += kirkwood_spi.o
 obj-$(CONFIG_LPC32XX_SSP) += lpc32xx_ssp.o
 obj-$(CONFIG_MPC8XX_SPI) += mpc8xx_spi.o
 obj-$(CONFIG_MPC8XXX_SPI) += mpc8xxx_spi.o
+obj-$(CONFIG_MT7621_SPI) += mt7621_spi.o
 obj-$(CONFIG_MVEBU_A3700_SPI) += mvebu_a3700_spi.o
 obj-$(CONFIG_MXC_SPI) += mxc_spi.o
 obj-$(CONFIG_MXS_SPI) += mxs_spi.o

drivers/spi/mt7621_spi.c

@@ -0,0 +1,312 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 Stefan Roese <sr@denx.de>
+ *
+ * Derived from the Linux driver version drivers/spi/spi-mt7621.c
+ *   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>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <spi.h>
+#include <wait_bit.h>
+#include <linux/io.h>
+
+#define SPI_MSG_SIZE_MAX	32	/* SPI message chunk size */
+/* Enough for SPI NAND page read / write with page size 2048 bytes */
+#define SPI_MSG_SIZE_OVERALL	(2048 + 16)
+
+#define MT7621_SPI_TRANS	0x00
+#define MT7621_SPI_TRANS_START	BIT(8)
+#define MT7621_SPI_TRANS_BUSY	BIT(16)
+
+#define MT7621_SPI_OPCODE	0x04
+#define MT7621_SPI_DATA0	0x08
+#define MT7621_SPI_DATA4	0x18
+#define MT7621_SPI_MASTER	0x28
+#define MT7621_SPI_MOREBUF	0x2c
+#define MT7621_SPI_POLAR	0x38
+
+#define MT7621_LSB_FIRST	BIT(3)
+#define MT7621_CPOL		BIT(4)
+#define MT7621_CPHA		BIT(5)
+
+#define MASTER_MORE_BUFMODE	BIT(2)
+#define MASTER_RS_CLK_SEL	GENMASK(27, 16)
+#define MASTER_RS_CLK_SEL_SHIFT	16
+#define MASTER_RS_SLAVE_SEL	GENMASK(31, 29)
+
+struct mt7621_spi {
+	void __iomem *base;
+	unsigned int sys_freq;
+	u32 data[(SPI_MSG_SIZE_OVERALL / 4) + 1];
+	int tx_len;
+};
+
+static void mt7621_spi_reset(struct mt7621_spi *rs, int duplex)
+{
+	setbits_le32(rs->base + MT7621_SPI_MASTER,
+		     MASTER_RS_SLAVE_SEL | MASTER_MORE_BUFMODE);
+}
+
+static void mt7621_spi_set_cs(struct mt7621_spi *rs, int cs, int enable)
+{
+	u32 val = 0;
+
+	debug("%s: cs#%d -> %s\n", __func__, cs, enable ? "enable" : "disable");
+	if (enable)
+		val = BIT(cs);
+	iowrite32(val, rs->base + MT7621_SPI_POLAR);
+}
+
+static int mt7621_spi_set_mode(struct udevice *bus, uint mode)
+{
+	struct mt7621_spi *rs = dev_get_priv(bus);
+	u32 reg;
+
+	debug("%s: mode=0x%08x\n", __func__, mode);
+	reg = ioread32(rs->base + MT7621_SPI_MASTER);
+
+	reg &= ~MT7621_LSB_FIRST;
+	if (mode & SPI_LSB_FIRST)
+		reg |= MT7621_LSB_FIRST;
+
+	reg &= ~(MT7621_CPHA | MT7621_CPOL);
+	switch (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;
+	}
+	iowrite32(reg, rs->base + MT7621_SPI_MASTER);
+
+	return 0;
+}
+
+static int mt7621_spi_set_speed(struct udevice *bus, uint speed)
+{
+	struct mt7621_spi *rs = dev_get_priv(bus);
+	u32 rate;
+	u32 reg;
+
+	debug("%s: speed=%d\n", __func__, speed);
+	rate = DIV_ROUND_UP(rs->sys_freq, speed);
+	debug("rate:%u\n", rate);
+
+	if (rate > 4097)
+		return -EINVAL;
+
+	if (rate < 2)
+		rate = 2;
+
+	reg = ioread32(rs->base + MT7621_SPI_MASTER);
+	reg &= ~MASTER_RS_CLK_SEL;
+	reg |= (rate - 2) << MASTER_RS_CLK_SEL_SHIFT;
+	iowrite32(reg, rs->base + MT7621_SPI_MASTER);
+
+	return 0;
+}
+
+static inline int mt7621_spi_wait_till_ready(struct mt7621_spi *rs)
+{
+	int ret;
+
+	ret =  wait_for_bit_le32(rs->base + MT7621_SPI_TRANS,
+				 MT7621_SPI_TRANS_BUSY, 0, 10, 0);
+	if (ret)
+		pr_err("Timeout in %s!\n", __func__);
+
+	return ret;
+}
+
+static int mt7621_spi_xfer(struct udevice *dev, unsigned int bitlen,
+			   const void *dout, void *din, unsigned long flags)
+{
+	struct udevice *bus = dev->parent;
+	struct mt7621_spi *rs = dev_get_priv(bus);
+	const u8 *tx_buf = dout;
+	u8 *ptr = (u8 *)dout;
+	u8 *rx_buf = din;
+	int total_size = bitlen >> 3;
+	int chunk_size;
+	int rx_len = 0;
+	u32 data[(SPI_MSG_SIZE_MAX / 4) + 1] = { 0 };
+	u32 val;
+	int i;
+
+	debug("%s: dout=%p, din=%p, len=%x, flags=%lx\n", __func__, dout, din,
+	      total_size, flags);
+
+	/*
+	 * This driver only supports half-duplex, so complain and bail out
+	 * upon full-duplex messages
+	 */
+	if (dout && din) {
+		printf("Only half-duplex SPI transfer supported\n");
+		return -EIO;
+	}
+
+	if (dout) {
+		debug("TX-DATA: ");
+		for (i = 0; i < total_size; i++)
+			debug("%02x ", *ptr++);
+		debug("\n");
+	}
+
+	mt7621_spi_wait_till_ready(rs);
+
+	/*
+	 * Set CS active upon start of SPI message. This message can
+	 * be split upon multiple calls to this xfer function
+	 */
+	if (flags & SPI_XFER_BEGIN)
+		mt7621_spi_set_cs(rs, spi_chip_select(dev), 1);
+
+	while (total_size > 0) {
+		/* Don't exceed the max xfer size */
+		chunk_size = min_t(int, total_size, SPI_MSG_SIZE_MAX);
+
+		/*
+		 * We might have some TX data buffered from the last xfer
+		 * message. Make sure, that this does not exceed the max
+		 * xfer size
+		 */
+		if (rs->tx_len > 4)
+			chunk_size -= rs->tx_len;
+		if (din)
+			rx_len = chunk_size;
+
+		if (tx_buf) {
+			/* Check if this message does not exceed the buffer */
+			if ((chunk_size + rs->tx_len) > SPI_MSG_SIZE_OVERALL) {
+				printf("TX message size too big (%d)\n",
+				       chunk_size + rs->tx_len);
+				return -EMSGSIZE;
+			}
+
+			/*
+			 * Write all TX data into internal buffer to collect
+			 * all TX messages into one buffer (might be split into
+			 * multiple calls to this function)
+			 */
+			for (i = 0; i < chunk_size; i++, rs->tx_len++) {
+				rs->data[rs->tx_len / 4] |=
+					tx_buf[i] << (8 * (rs->tx_len & 3));
+			}
+		}
+
+		if (flags & SPI_XFER_END) {
+			/* Write TX data into controller */
+			if (rs->tx_len) {
+				rs->data[0] = swab32(rs->data[0]);
+				if (rs->tx_len < 4)
+					rs->data[0] >>= (4 - rs->tx_len) * 8;
+
+				for (i = 0; i < rs->tx_len; i += 4) {
+					iowrite32(rs->data[i / 4], rs->base +
+						  MT7621_SPI_OPCODE + i);
+				}
+			}
+
+			/* Write length into controller */
+			val = (min_t(int, rs->tx_len, 4) * 8) << 24;
+			if (rs->tx_len > 4)
+				val |= (rs->tx_len - 4) * 8;
+			val |= (rx_len * 8) << 12;
+			iowrite32(val, rs->base + MT7621_SPI_MOREBUF);
+
+			/* Start the xfer */
+			setbits_le32(rs->base + MT7621_SPI_TRANS,
+				     MT7621_SPI_TRANS_START);
+
+			/* Wait until xfer is finished on bus */
+			mt7621_spi_wait_till_ready(rs);
+
+			/* Reset TX length and TX buffer for next xfer */
+			rs->tx_len = 0;
+			memset(rs->data, 0, sizeof(rs->data));
+		}
+
+		for (i = 0; i < rx_len; i += 4)
+			data[i / 4] = ioread32(rs->base + MT7621_SPI_DATA0 + i);
+
+		if (rx_len) {
+			debug("RX-DATA: ");
+			for (i = 0; i < rx_len; i++) {
+				rx_buf[i] = data[i / 4] >> (8 * (i & 3));
+				debug("%02x ", rx_buf[i]);
+			}
+			debug("\n");
+		}
+
+		if (tx_buf)
+			tx_buf += chunk_size;
+		if (rx_buf)
+			rx_buf += chunk_size;
+		total_size -= chunk_size;
+	}
+
+	/* Wait until xfer is finished on bus and de-assert CS */
+	mt7621_spi_wait_till_ready(rs);
+	if (flags & SPI_XFER_END)
+		mt7621_spi_set_cs(rs, spi_chip_select(dev), 0);
+
+	return 0;
+}
+
+static int mt7621_spi_probe(struct udevice *dev)
+{
+	struct mt7621_spi *rs = dev_get_priv(dev);
+
+	rs->base = dev_remap_addr(dev);
+	if (!rs->base)
+		return -EINVAL;
+
+	/*
+	 * Read input clock via DT for now. At some point this should be
+	 * replaced by implementing a clock driver for this SoC and getting
+	 * the SPI frequency via this clock driver.
+	 */
+	rs->sys_freq = dev_read_u32_default(dev, "clock-frequency", 0);
+	if (!rs->sys_freq) {
+		printf("Please provide clock-frequency!\n");
+		return -EINVAL;
+	}
+
+	mt7621_spi_reset(rs, 0);
+
+	return 0;
+}
+
+static const struct dm_spi_ops mt7621_spi_ops = {
+	.set_mode = mt7621_spi_set_mode,
+	.set_speed = mt7621_spi_set_speed,
+	.xfer = mt7621_spi_xfer,
+	/*
+	 * cs_info is not needed, since we require all chip selects to be
+	 * in the device tree explicitly
+	 */
+};
+
+static const struct udevice_id mt7621_spi_ids[] = {
+	{ .compatible = "ralink,mt7621-spi" },
+	{ }
+};
+
+U_BOOT_DRIVER(mt7621_spi) = {
+	.name = "mt7621_spi",
+	.id = UCLASS_SPI,
+	.of_match = mt7621_spi_ids,
+	.ops = &mt7621_spi_ops,
+	.priv_auto_alloc_size = sizeof(struct mt7621_spi),
+	.probe = mt7621_spi_probe,
+};