spi: pic32_spi: add SPI master driver for PIC32 SoC.

This driver implements SPI protocol in master mode to communicate
with the SPI device connected on SPI bus. It handles /CS explicitly
by controlling respective pin as gpio ('cs-gpios' property in dt node)
and uses PIO mode for SPI transaction. It is configurable based
on driver-model only.

Cc: Jagan Teki <jteki@openedev.com>
Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

1 files changed, 448 insertions, 0 deletions

diff --git a/drivers/spi/pic32_spi.c b/drivers/spi/pic32_spi.c
new file mode 100644
index 0000000000..25ca1f3e1b
--- /dev/null
+++ b/drivers/spi/pic32_spi.c
@@ -0,0 +1,448 @@
+/*
+ * Microchip PIC32 SPI controller driver.
+ *
+ * Copyright (c) 2015, Microchip Technology Inc.
+ *      Purna Chandra Mandal <purna.mandal@microchip.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <linux/compat.h>
+#include <malloc.h>
+#include <spi.h>
+
+#include <asm/types.h>
+#include <asm/io.h>
+#include <asm/gpio.h>
+#include <dt-bindings/clock/microchip,clock.h>
+#include <mach/pic32.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/* PIC32 SPI controller registers */
+struct pic32_reg_spi {
+	struct pic32_reg_atomic ctrl;
+	struct pic32_reg_atomic status;
+	struct pic32_reg_atomic buf;
+	struct pic32_reg_atomic baud;
+	struct pic32_reg_atomic ctrl2;
+};
+
+/* Bit fields in SPI Control Register */
+#define PIC32_SPI_CTRL_MSTEN	BIT(5) /* Enable SPI Master */
+#define PIC32_SPI_CTRL_CKP	BIT(6) /* active low */
+#define PIC32_SPI_CTRL_CKE	BIT(8) /* Tx on falling edge */
+#define PIC32_SPI_CTRL_SMP	BIT(9) /* Rx at middle or end of tx */
+#define PIC32_SPI_CTRL_BPW_MASK	0x03   /* Bits per word */
+#define  PIC32_SPI_CTRL_BPW_8		0x0
+#define  PIC32_SPI_CTRL_BPW_16		0x1
+#define  PIC32_SPI_CTRL_BPW_32		0x2
+#define PIC32_SPI_CTRL_BPW_SHIFT	10
+#define PIC32_SPI_CTRL_ON	BIT(15) /* Macro enable */
+#define PIC32_SPI_CTRL_ENHBUF	BIT(16) /* Enable enhanced buffering */
+#define PIC32_SPI_CTRL_MCLKSEL	BIT(23) /* Select SPI Clock src */
+#define PIC32_SPI_CTRL_MSSEN	BIT(28) /* SPI macro will drive SS */
+#define PIC32_SPI_CTRL_FRMEN	BIT(31) /* Enable framing mode */
+
+/* Bit fields in SPI Status Register */
+#define PIC32_SPI_STAT_RX_OV		BIT(6) /* err, s/w needs to clear */
+#define PIC32_SPI_STAT_TF_LVL_MASK	0x1f
+#define PIC32_SPI_STAT_TF_LVL_SHIFT	16
+#define PIC32_SPI_STAT_RF_LVL_MASK	0x1f
+#define PIC32_SPI_STAT_RF_LVL_SHIFT	24
+
+/* Bit fields in SPI Baud Register */
+#define PIC32_SPI_BAUD_MASK	0x1ff
+
+struct pic32_spi_priv {
+	struct pic32_reg_spi	*regs;
+	u32			fifo_depth; /* FIFO depth in bytes */
+	u32			fifo_n_word; /* FIFO depth in words */
+	struct gpio_desc	cs_gpio;
+
+	/* Current SPI slave specific */
+	ulong			clk_rate;
+	u32			speed_hz; /* spi-clk rate */
+	int			mode;
+
+	/* Current message/transfer state */
+	const void		*tx;
+	const void		*tx_end;
+	const void		*rx;
+	const void		*rx_end;
+	u32			len;
+
+	/* SPI FiFo accessor */
+	void (*rx_fifo)(struct pic32_spi_priv *);
+	void (*tx_fifo)(struct pic32_spi_priv *);
+};
+
+static inline void pic32_spi_enable(struct pic32_spi_priv *priv)
+{
+	writel(PIC32_SPI_CTRL_ON, &priv->regs->ctrl.set);
+}
+
+static inline void pic32_spi_disable(struct pic32_spi_priv *priv)
+{
+	writel(PIC32_SPI_CTRL_ON, &priv->regs->ctrl.clr);
+}
+
+static inline u32 pic32_spi_rx_fifo_level(struct pic32_spi_priv *priv)
+{
+	u32 sr = readl(&priv->regs->status.raw);
+
+	return (sr >> PIC32_SPI_STAT_RF_LVL_SHIFT) & PIC32_SPI_STAT_RF_LVL_MASK;
+}
+
+static inline u32 pic32_spi_tx_fifo_level(struct pic32_spi_priv *priv)
+{
+	u32 sr = readl(&priv->regs->status.raw);
+
+	return (sr >> PIC32_SPI_STAT_TF_LVL_SHIFT) & PIC32_SPI_STAT_TF_LVL_MASK;
+}
+
+/* Return the max entries we can fill into tx fifo */
+static u32 pic32_tx_max(struct pic32_spi_priv *priv, int n_bytes)
+{
+	u32 tx_left, tx_room, rxtx_gap;
+
+	tx_left = (priv->tx_end - priv->tx) / n_bytes;
+	tx_room = priv->fifo_n_word - pic32_spi_tx_fifo_level(priv);
+
+	rxtx_gap = (priv->rx_end - priv->rx) - (priv->tx_end - priv->tx);
+	rxtx_gap /= n_bytes;
+	return min3(tx_left, tx_room, (u32)(priv->fifo_n_word - rxtx_gap));
+}
+
+/* Return the max entries we should read out of rx fifo */
+static u32 pic32_rx_max(struct pic32_spi_priv *priv, int n_bytes)
+{
+	u32 rx_left = (priv->rx_end - priv->rx) / n_bytes;
+
+	return min_t(u32, rx_left, pic32_spi_rx_fifo_level(priv));
+}
+
+#define BUILD_SPI_FIFO_RW(__name, __type, __bwl)		\
+static void pic32_spi_rx_##__name(struct pic32_spi_priv *priv)	\
+{								\
+	__type val;						\
+	u32 mx = pic32_rx_max(priv, sizeof(__type));		\
+								\
+	for (; mx; mx--) {					\
+		val = read##__bwl(&priv->regs->buf.raw);	\
+		if (priv->rx_end - priv->len)			\
+			*(__type *)(priv->rx) = val;		\
+		priv->rx += sizeof(__type);			\
+	}							\
+}								\
+								\
+static void pic32_spi_tx_##__name(struct pic32_spi_priv *priv)	\
+{								\
+	__type val;						\
+	u32 mx = pic32_tx_max(priv, sizeof(__type));		\
+								\
+	for (; mx ; mx--) {					\
+		val = (__type) ~0U;				\
+		if (priv->tx_end - priv->len)			\
+			val =  *(__type *)(priv->tx);		\
+		write##__bwl(val, &priv->regs->buf.raw);	\
+		priv->tx += sizeof(__type);			\
+	}							\
+}
+BUILD_SPI_FIFO_RW(byte, u8, b);
+BUILD_SPI_FIFO_RW(word, u16, w);
+BUILD_SPI_FIFO_RW(dword, u32, l);
+
+static int pic32_spi_set_word_size(struct pic32_spi_priv *priv,
+				   unsigned int wordlen)
+{
+	u32 bits_per_word;
+	u32 val;
+
+	switch (wordlen) {
+	case 8:
+		priv->rx_fifo = pic32_spi_rx_byte;
+		priv->tx_fifo = pic32_spi_tx_byte;
+		bits_per_word = PIC32_SPI_CTRL_BPW_8;
+		break;
+	case 16:
+		priv->rx_fifo = pic32_spi_rx_word;
+		priv->tx_fifo = pic32_spi_tx_word;
+		bits_per_word = PIC32_SPI_CTRL_BPW_16;
+		break;
+	case 32:
+		priv->rx_fifo = pic32_spi_rx_dword;
+		priv->tx_fifo = pic32_spi_tx_dword;
+		bits_per_word = PIC32_SPI_CTRL_BPW_32;
+		break;
+	default:
+		printf("pic32-spi: unsupported wordlen\n");
+		return -EINVAL;
+	}
+
+	/* set bits-per-word */
+	val = readl(&priv->regs->ctrl.raw);
+	val &= ~(PIC32_SPI_CTRL_BPW_MASK << PIC32_SPI_CTRL_BPW_SHIFT);
+	val |= bits_per_word << PIC32_SPI_CTRL_BPW_SHIFT;
+	writel(val, &priv->regs->ctrl.raw);
+
+	/* calculate maximum number of words fifo can hold */
+	priv->fifo_n_word = DIV_ROUND_UP(priv->fifo_depth, wordlen / 8);
+
+	return 0;
+}
+
+static int pic32_spi_claim_bus(struct udevice *slave)
+{
+	struct pic32_spi_priv *priv = dev_get_priv(slave->parent);
+
+	/* enable chip */
+	pic32_spi_enable(priv);
+
+	return 0;
+}
+
+static int pic32_spi_release_bus(struct udevice *slave)
+{
+	struct pic32_spi_priv *priv = dev_get_priv(slave->parent);
+
+	/* disable chip */
+	pic32_spi_disable(priv);
+
+	return 0;
+}
+
+static void spi_cs_activate(struct pic32_spi_priv *priv)
+{
+	if (!dm_gpio_is_valid(&priv->cs_gpio))
+		return;
+
+	dm_gpio_set_value(&priv->cs_gpio, 1);
+}
+
+static void spi_cs_deactivate(struct pic32_spi_priv *priv)
+{
+	if (!dm_gpio_is_valid(&priv->cs_gpio))
+		return;
+
+	dm_gpio_set_value(&priv->cs_gpio, 0);
+}
+
+static int pic32_spi_xfer(struct udevice *slave, unsigned int bitlen,
+			  const void *tx_buf, void *rx_buf,
+			  unsigned long flags)
+{
+	struct dm_spi_slave_platdata *slave_plat;
+	struct udevice *bus = slave->parent;
+	struct pic32_spi_priv *priv;
+	int len = bitlen / 8;
+	int ret = 0;
+	ulong tbase;
+
+	priv = dev_get_priv(bus);
+	slave_plat = dev_get_parent_platdata(slave);
+
+	debug("spi_xfer: bus:%i cs:%i flags:%lx\n",
+	      bus->seq, slave_plat->cs, flags);
+	debug("msg tx %p, rx %p submitted of %d byte(s)\n",
+	      tx_buf, rx_buf, len);
+
+	/* assert cs */
+	if (flags & SPI_XFER_BEGIN)
+		spi_cs_activate(priv);
+
+	/* set current transfer information */
+	priv->tx = tx_buf;
+	priv->rx = rx_buf;
+	priv->tx_end = priv->tx + len;
+	priv->rx_end = priv->rx + len;
+	priv->len = len;
+
+	/* transact by polling */
+	tbase = get_timer(0);
+	for (;;) {
+		priv->tx_fifo(priv);
+		priv->rx_fifo(priv);
+
+		/* received sufficient data */
+		if (priv->rx >= priv->rx_end) {
+			ret = 0;
+			break;
+		}
+
+		if (get_timer(tbase) > 5 * CONFIG_SYS_HZ) {
+			printf("pic32_spi: error, xfer timedout.\n");
+			flags |= SPI_XFER_END;
+			ret = -ETIMEDOUT;
+			break;
+		}
+	}
+
+	/* deassert cs */
+	if (flags & SPI_XFER_END)
+		spi_cs_deactivate(priv);
+
+	return ret;
+}
+
+static int pic32_spi_set_speed(struct udevice *bus, uint speed)
+{
+	struct pic32_spi_priv *priv = dev_get_priv(bus);
+	u32 div;
+
+	debug("%s: %s, speed %u\n", __func__, bus->name, speed);
+
+	/* div = [clk_in / (2 * spi_clk)] - 1 */
+	div = (priv->clk_rate / 2 / speed) - 1;
+	div &= PIC32_SPI_BAUD_MASK;
+	writel(div, &priv->regs->baud.raw);
+
+	priv->speed_hz = speed;
+
+	return 0;
+}
+
+static int pic32_spi_set_mode(struct udevice *bus, uint mode)
+{
+	struct pic32_spi_priv *priv = dev_get_priv(bus);
+	u32 val;
+
+	debug("%s: %s, mode %d\n", __func__, bus->name, mode);
+
+	/* set spi-clk mode */
+	val = readl(&priv->regs->ctrl.raw);
+	/* HIGH when idle */
+	if (mode & SPI_CPOL)
+		val |= PIC32_SPI_CTRL_CKP;
+	else
+		val &= ~PIC32_SPI_CTRL_CKP;
+
+	/* TX at idle-to-active clk transition */
+	if (mode & SPI_CPHA)
+		val &= ~PIC32_SPI_CTRL_CKE;
+	else
+		val |= PIC32_SPI_CTRL_CKE;
+
+	/* RX at end of tx */
+	val |= PIC32_SPI_CTRL_SMP;
+	writel(val, &priv->regs->ctrl.raw);
+
+	priv->mode = mode;
+
+	return 0;
+}
+
+static int pic32_spi_set_wordlen(struct udevice *slave, unsigned int wordlen)
+{
+	struct pic32_spi_priv *priv = dev_get_priv(slave->parent);
+
+	return pic32_spi_set_word_size(priv, wordlen);
+}
+
+static void pic32_spi_hw_init(struct pic32_spi_priv *priv)
+{
+	u32 val;
+
+	/* disable module */
+	pic32_spi_disable(priv);
+
+	val = readl(&priv->regs->ctrl);
+
+	/* enable enhanced fifo of 128bit deep */
+	val |= PIC32_SPI_CTRL_ENHBUF;
+	priv->fifo_depth = 16;
+
+	/* disable framing mode */
+	val &= ~PIC32_SPI_CTRL_FRMEN;
+
+	/* enable master mode */
+	val |= PIC32_SPI_CTRL_MSTEN;
+
+	/* select clk source */
+	val &= ~PIC32_SPI_CTRL_MCLKSEL;
+
+	/* set manual /CS mode */
+	val &= ~PIC32_SPI_CTRL_MSSEN;
+
+	writel(val, &priv->regs->ctrl);
+
+	/* clear rx overflow indicator */
+	writel(PIC32_SPI_STAT_RX_OV, &priv->regs->status.clr);
+}
+
+static int pic32_spi_probe(struct udevice *bus)
+{
+	struct pic32_spi_priv *priv = dev_get_priv(bus);
+	struct dm_spi_bus *dm_spi = dev_get_uclass_priv(bus);
+	struct udevice *clkdev;
+	fdt_addr_t addr;
+	fdt_size_t size;
+	int ret;
+
+	debug("%s: %d, bus: %i\n", __func__, __LINE__, bus->seq);
+	addr = fdtdec_get_addr_size(gd->fdt_blob, bus->of_offset, "reg", &size);
+	if (addr == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	priv->regs = ioremap(addr, size);
+	if (!priv->regs)
+		return -EINVAL;
+
+	dm_spi->max_hz = fdtdec_get_int(gd->fdt_blob, bus->of_offset,
+					"spi-max-frequency", 250000000);
+	/* get clock rate */
+	ret = clk_get_by_index(bus, 0, &clkdev);
+	if (ret < 0) {
+		printf("pic32-spi: error, clk not found\n");
+		return ret;
+	}
+	priv->clk_rate = clk_get_periph_rate(clkdev, ret);
+
+	/* initialize HW */
+	pic32_spi_hw_init(priv);
+
+	/* set word len */
+	pic32_spi_set_word_size(priv, SPI_DEFAULT_WORDLEN);
+
+	/* PIC32 SPI controller can automatically drive /CS during transfer
+	 * depending on fifo fill-level. /CS will stay asserted as long as
+	 * TX fifo is non-empty, else will be deasserted confirming completion
+	 * of the ongoing transfer. To avoid this sort of error we will drive
+	 * /CS manually by toggling cs-gpio pins.
+	 */
+	ret = gpio_request_by_name_nodev(gd->fdt_blob, bus->of_offset,
+					 "cs-gpios", 0,
+					 &priv->cs_gpio, GPIOD_IS_OUT);
+	if (ret) {
+		printf("pic32-spi: error, cs-gpios not found\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct dm_spi_ops pic32_spi_ops = {
+	.claim_bus	= pic32_spi_claim_bus,
+	.release_bus	= pic32_spi_release_bus,
+	.xfer		= pic32_spi_xfer,
+	.set_speed	= pic32_spi_set_speed,
+	.set_mode	= pic32_spi_set_mode,
+	.set_wordlen	= pic32_spi_set_wordlen,
+};
+
+static const struct udevice_id pic32_spi_ids[] = {
+	{ .compatible = "microchip,pic32mzda-spi" },
+	{ }
+};
+
+U_BOOT_DRIVER(pic32_spi) = {
+	.name		= "pic32_spi",
+	.id		= UCLASS_SPI,
+	.of_match	= pic32_spi_ids,
+	.ops		= &pic32_spi_ops,
+	.priv_auto_alloc_size = sizeof(struct pic32_spi_priv),
+	.probe		= pic32_spi_probe,
+};