[PATCH v2 2/2] spi: pic32-sqi: add SPI driver for PIC32 SQI controller.

[Purna Chandra Mandal <purna.mandal@xxxxxxxxxxxxx>]

This driver implements SPI master interface for Quad SPI
controller, specifically for accessing quad SPI flash.
It uses descriptor-based DMA transfer mode and supports
half-duplex communication for single, dual and quad SPI
transactions.

Signed-off-by: Purna Chandra Mandal <purna.mandal@xxxxxxxxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>

---

 drivers/spi/Kconfig         |   6 +
 drivers/spi/Makefile        |   1 +
 drivers/spi/spi-pic32-sqi.c | 815 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 822 insertions(+)
 create mode 100644 drivers/spi/spi-pic32-sqi.c

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 8a8ff50..281ed5d 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -442,6 +442,12 @@ config SPI_PIC32
 	help
 	  SPI driver for Microchip PIC32 SPI master controller.
 
+config SPI_PIC32_SQI
+	tristate "Microchip PIC32 Quad SPI driver"
+	depends on MACH_PIC32 || COMPILE_TEST
+	help
+	  SPI driver for PIC32 Quad SPI controller.
+
 config SPI_PL022
 	tristate "ARM AMBA PL022 SSP controller"
 	depends on ARM_AMBA
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 06019ed..3c74d00 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -63,6 +63,7 @@ obj-$(CONFIG_SPI_OMAP24XX)		+= spi-omap2-mcspi.o
 obj-$(CONFIG_SPI_TI_QSPI)		+= spi-ti-qspi.o
 obj-$(CONFIG_SPI_ORION)			+= spi-orion.o
 obj-$(CONFIG_SPI_PIC32)			+= spi-pic32.o
+obj-$(CONFIG_SPI_PIC32_SQI)		+= spi-pic32-sqi.o
 obj-$(CONFIG_SPI_PL022)			+= spi-pl022.o
 obj-$(CONFIG_SPI_PPC4xx)		+= spi-ppc4xx.o
 spi-pxa2xx-platform-objs		:= spi-pxa2xx.o spi-pxa2xx-dma.o
diff --git a/drivers/spi/spi-pic32-sqi.c b/drivers/spi/spi-pic32-sqi.c
new file mode 100644
index 0000000..bb31dc8
--- /dev/null
+++ b/drivers/spi/spi-pic32-sqi.c
@@ -0,0 +1,815 @@
+/*
+ * PIC32 Quad SPI controller driver.
+ *
+ * Purna Chandra Mandal <purna.mandal@xxxxxxxxxxxxx>
+ * Copyright (c) 2016, Microchip Technology Inc.
+ *
+ * This program is free software; you can distribute it and/or modify it
+ * under the terms of the GNU General Public License (Version 2) as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+#include <linux/clk.h>
+#include <linux/dma-mapping.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/spi/spi.h>
+
+/* SQI registers */
+#define PESQI_XIP_CONF1_REG	0x00
+#define PESQI_XIP_CONF2_REG	0x04
+#define PESQI_CONF_REG		0x08
+#define PESQI_CTRL_REG		0x0C
+#define PESQI_CLK_CTRL_REG	0x10
+#define PESQI_CMD_THRES_REG	0x14
+#define PESQI_INT_THRES_REG	0x18
+#define PESQI_INT_ENABLE_REG	0x1C
+#define PESQI_INT_STAT_REG	0x20
+#define PESQI_TX_DATA_REG	0x24
+#define PESQI_RX_DATA_REG	0x28
+#define PESQI_STAT1_REG		0x2C
+#define PESQI_STAT2_REG		0x30
+#define PESQI_BD_CTRL_REG	0x34
+#define PESQI_BD_CUR_ADDR_REG	0x38
+#define PESQI_BD_BASE_ADDR_REG	0x40
+#define PESQI_BD_STAT_REG	0x44
+#define PESQI_BD_POLL_CTRL_REG	0x48
+#define PESQI_BD_TX_DMA_STAT_REG	0x4C
+#define PESQI_BD_RX_DMA_STAT_REG	0x50
+#define PESQI_THRES_REG		0x54
+#define PESQI_INT_SIGEN_REG	0x58
+
+/* PESQI_CONF_REG fields */
+#define PESQI_MODE		0x7
+#define  PESQI_MODE_BOOT	0
+#define  PESQI_MODE_PIO		1
+#define  PESQI_MODE_DMA		2
+#define  PESQI_MODE_XIP		3
+#define PESQI_MODE_SHIFT	0
+#define PESQI_CPHA		BIT(3)
+#define PESQI_CPOL		BIT(4)
+#define PESQI_LSBF		BIT(5)
+#define PESQI_RXLATCH		BIT(7)
+#define PESQI_SERMODE		BIT(8)
+#define PESQI_WP_EN		BIT(9)
+#define PESQI_HOLD_EN		BIT(10)
+#define PESQI_BURST_EN		BIT(12)
+#define PESQI_CS_CTRL_HW	BIT(15)
+#define PESQI_SOFT_RESET	BIT(16)
+#define PESQI_LANES_SHIFT	20
+#define  PESQI_SINGLE_LANE	0
+#define  PESQI_DUAL_LANE	1
+#define  PESQI_QUAD_LANE	2
+#define PESQI_CSEN_SHIFT	24
+#define PESQI_EN		BIT(23)
+
+/* PESQI_CLK_CTRL_REG fields */
+#define PESQI_CLK_EN		BIT(0)
+#define PESQI_CLK_STABLE	BIT(1)
+#define PESQI_CLKDIV_SHIFT	8
+#define PESQI_CLKDIV		0xff
+
+/* PESQI_INT_THR/CMD_THR_REG */
+#define PESQI_TXTHR_MASK	0x1f
+#define PESQI_TXTHR_SHIFT	8
+#define PESQI_RXTHR_MASK	0x1f
+#define PESQI_RXTHR_SHIFT	0
+
+/* PESQI_INT_EN/INT_STAT/INT_SIG_EN_REG */
+#define PESQI_TXEMPTY		BIT(0)
+#define PESQI_TXFULL		BIT(1)
+#define PESQI_TXTHR		BIT(2)
+#define PESQI_RXEMPTY		BIT(3)
+#define PESQI_RXFULL		BIT(4)
+#define PESQI_RXTHR		BIT(5)
+#define PESQI_BDDONE		BIT(9)  /* BD processing complete */
+#define PESQI_PKTCOMP		BIT(10) /* packet processing complete */
+#define PESQI_DMAERR		BIT(11) /* error */
+
+/* PESQI_BD_CTRL_REG */
+#define PESQI_DMA_EN		BIT(0) /* enable DMA engine */
+#define PESQI_POLL_EN		BIT(1) /* enable polling */
+#define PESQI_BDP_START		BIT(2) /* start BD processor */
+
+/* PESQI controller buffer descriptor */
+struct buf_desc {
+	u32 bd_ctrl;	/* control */
+	u32 bd_status;	/* reserved */
+	u32 bd_addr;	/* DMA buffer addr */
+	u32 bd_nextp;	/* next item in chain */
+};
+
+/* bd_ctrl */
+#define BD_BUFLEN		0x1ff
+#define BD_CBD_INT_EN		BIT(16)	/* Current BD is processed */
+#define BD_PKT_INT_EN		BIT(17) /* All BDs of PKT processed */
+#define BD_LIFM			BIT(18) /* last data of pkt */
+#define BD_LAST			BIT(19) /* end of list */
+#define BD_DATA_RECV		BIT(20) /* receive data */
+#define BD_DDR			BIT(21) /* DDR mode */
+#define BD_DUAL			BIT(22)	/* Dual SPI */
+#define BD_QUAD			BIT(23) /* Quad SPI */
+#define BD_LSBF			BIT(25)	/* LSB First */
+#define BD_STAT_CHECK		BIT(27) /* Status poll */
+#define BD_DEVSEL_SHIFT		28	/* CS */
+#define BD_CS_DEASSERT		BIT(30) /* de-assert CS after current BD */
+#define BD_EN			BIT(31) /* BD owned by H/W */
+
+/**
+ * struct ring_desc - Representation of SQI ring descriptor
+ * @list:	list element to add to free or used list.
+ * @bd:		PESQI controller buffer descriptor
+ * @bd_dma:	DMA address of PESQI controller buffer descriptor
+ * @xfer_len:	transfer length
+ */
+struct ring_desc {
+	struct list_head list;
+	struct buf_desc *bd;
+	dma_addr_t bd_dma;
+	u32 xfer_len;
+};
+
+/* Global constants */
+#define PESQI_BD_BUF_LEN_MAX	SZ_256
+#define PESQI_BD_COUNT		SZ_256 /* max 64KB data per spi message */
+
+struct pic32_sqi {
+	void __iomem		*regs;
+	struct clk		*sys_clk;
+	struct clk		*base_clk; /* drives spi clock */
+	struct spi_master	*master;
+	int			irq;
+	struct completion	xfer_done;
+	struct ring_desc	*ring;
+	void			*bd;
+	dma_addr_t		bd_dma;
+	struct list_head	bd_list_free; /* free */
+	struct list_head	bd_list_used; /* allocated */
+	struct spi_device	*cur_spi;
+	u32			cur_speed;
+	u8			cur_mode;
+};
+
+static inline void pic32_setbits(void __iomem *reg, u32 set)
+{
+	writel(readl(reg) | set, reg);
+}
+
+static inline void pic32_clrbits(void __iomem *reg, u32 clr)
+{
+	writel(readl(reg) & ~clr, reg);
+}
+
+static int pic32_sqi_set_clk_rate(struct pic32_sqi *sqi, u32 sck)
+{
+	u32 val, div;
+
+	/* div = base_clk / (2 * spi_clk) */
+	div = clk_get_rate(sqi->base_clk) / (2 * sck);
+	div &= PESQI_CLKDIV;
+
+	val = readl(sqi->regs + PESQI_CLK_CTRL_REG);
+	/* apply new divider */
+	val &= ~(PESQI_CLK_STABLE | (PESQI_CLKDIV << PESQI_CLKDIV_SHIFT));
+	val |= div << PESQI_CLKDIV_SHIFT;
+	writel(val, sqi->regs + PESQI_CLK_CTRL_REG);
+
+	/* wait for stability */
+	return readl_poll_timeout(sqi->regs + PESQI_CLK_CTRL_REG, val,
+				  val & PESQI_CLK_STABLE, 1, 5000);
+}
+
+static inline void pic32_sqi_enable_int(struct pic32_sqi *sqi)
+{
+	u32 mask = PESQI_DMAERR | PESQI_BDDONE | PESQI_PKTCOMP;
+
+	writel(mask, sqi->regs + PESQI_INT_ENABLE_REG);
+	/* INT_SIGEN works as interrupt-gate to INTR line */
+	writel(mask, sqi->regs + PESQI_INT_SIGEN_REG);
+}
+
+static inline void pic32_sqi_disable_int(struct pic32_sqi *sqi)
+{
+	writel(0, sqi->regs + PESQI_INT_ENABLE_REG);
+	writel(0, sqi->regs + PESQI_INT_SIGEN_REG);
+}
+
+static irqreturn_t pic32_sqi_isr(int irq, void *dev_id)
+{
+	struct pic32_sqi *sqi = dev_id;
+	u32 enable, status;
+
+	enable = readl(sqi->regs + PESQI_INT_ENABLE_REG);
+	status = readl(sqi->regs + PESQI_INT_STAT_REG);
+	if (!status)
+		return IRQ_NONE;
+
+	if (status & PESQI_DMAERR) {
+		enable = 0;
+		goto irq_done;
+	}
+
+	if (status & PESQI_TXTHR)
+		enable &= ~(PESQI_TXTHR | PESQI_TXFULL | PESQI_TXEMPTY);
+
+	if (status & PESQI_RXTHR)
+		enable &= ~(PESQI_RXTHR | PESQI_RXFULL | PESQI_RXEMPTY);
+
+	if (status & PESQI_BDDONE)
+		enable &= ~PESQI_BDDONE;
+
+	/* packet processing completed */
+	if (status & PESQI_PKTCOMP) {
+		/* mask all interrupts */
+		enable = 0;
+		/* complete trasaction */
+		complete(&sqi->xfer_done);
+	}
+
+irq_done:
+	/* interrupts are sticky, so mask when handled */
+	writel(enable, sqi->regs + PESQI_INT_ENABLE_REG);
+
+	return IRQ_HANDLED;
+}
+
+static struct ring_desc *ring_desc_get(struct pic32_sqi *sqi)
+{
+	struct ring_desc *rdesc;
+
+	if (list_empty(&sqi->bd_list_free))
+		return NULL;
+
+	rdesc = list_first_entry(&sqi->bd_list_free, struct ring_desc, list);
+	list_del(&rdesc->list);
+	list_add_tail(&rdesc->list, &sqi->bd_list_used);
+	return rdesc;
+}
+
+static void ring_desc_put(struct pic32_sqi *sqi, struct ring_desc *rdesc)
+{
+	list_del(&rdesc->list);
+	list_add(&rdesc->list, &sqi->bd_list_free);
+}
+
+static dma_addr_t pic32_sqi_map_transfer(struct pic32_sqi *sqi,
+					 struct spi_transfer *transfer)
+{
+	struct device *dev = &sqi->master->dev;
+	const int len = transfer->len;
+	enum dma_data_direction dir;
+	dma_addr_t dma_buf;
+	const void *buf;
+
+	transfer->rx_dma = 0;
+	transfer->tx_dma = 0;
+
+	if (transfer->rx_buf) {
+		buf = transfer->rx_buf;
+		dir = DMA_FROM_DEVICE;
+	} else {
+		buf = transfer->tx_buf;
+		dir = DMA_TO_DEVICE;
+	}
+
+	if (is_vmalloc_addr(buf))
+		dma_buf = dma_map_page(dev, vmalloc_to_page(buf),
+				       offset_in_page(buf), len, dir);
+	else
+		dma_buf = dma_map_single(dev, (void *)buf, len, dir);
+
+	if (dma_mapping_error(dev, dma_buf))
+		return 0;
+
+	if (transfer->rx_buf)
+		transfer->rx_dma = dma_buf;
+	else
+		transfer->tx_dma = dma_buf;
+
+	return dma_buf;
+}
+
+static void pic32_sqi_unmap_transfer(struct pic32_sqi *sqi,
+				     struct spi_transfer *transfer)
+{
+	struct device *dev = &sqi->master->dev;
+	const int len = transfer->len;
+	enum dma_data_direction dir;
+	dma_addr_t dma_buf;
+	const void *buf;
+
+	if (transfer->rx_buf) {
+		buf = transfer->rx_buf;
+		dma_buf = transfer->rx_dma;
+		dir = DMA_FROM_DEVICE;
+	} else {
+		buf = transfer->tx_buf;
+		dma_buf = transfer->tx_dma;
+		dir = DMA_TO_DEVICE;
+	}
+
+	if (is_vmalloc_addr(buf))
+		dma_unmap_page(dev, dma_buf, len, dir);
+	else
+		dma_unmap_single(dev, dma_buf, len, dir);
+}
+
+static int pic32_sqi_one_transfer(struct pic32_sqi *sqi,
+				  struct spi_message *mesg,
+				  struct spi_transfer *xfer)
+{
+	struct spi_device *spi = mesg->spi;
+	struct ring_desc *rdesc;
+	dma_addr_t dma_buf;
+	int remaining, offset;
+	struct buf_desc *bd;
+	u32 bd_ctrl;
+	u32 nbits;
+
+	/* Device selection */
+	bd_ctrl = spi->chip_select << BD_DEVSEL_SHIFT;
+
+	/* half-duplex: select transfer direction and lane */
+	if (xfer->rx_buf) {
+		bd_ctrl |= BD_DATA_RECV;
+		nbits = xfer->rx_nbits;
+	} else {
+		nbits = xfer->tx_nbits;
+	}
+
+	if (nbits & SPI_NBITS_QUAD)
+		bd_ctrl |= BD_QUAD;
+	else if (nbits & SPI_NBITS_DUAL)
+		bd_ctrl |= BD_DUAL;
+
+	/* LSB first */
+	if (spi->mode & SPI_LSB_FIRST)
+		bd_ctrl |= BD_LSBF;
+
+	/* ownership to hardware */
+	bd_ctrl |= BD_EN;
+
+	dma_buf = pic32_sqi_map_transfer(sqi, xfer);
+	if (!dma_buf)
+		return -EPERM;
+
+	/* fill BDs - one BD can handle upto 256 byte of data */
+	for (offset = 0, remaining = xfer->len; remaining;) {
+		/* get ring descriptor */
+		rdesc = ring_desc_get(sqi);
+		if (!rdesc)
+			break;
+
+		rdesc->xfer_len = min_t(u32, remaining, PESQI_BD_BUF_LEN_MAX);
+
+		bd = rdesc->bd;
+
+		/* BD CTRL: length */
+		bd->bd_ctrl = bd_ctrl;
+		bd->bd_ctrl |= rdesc->xfer_len;
+
+		/* BD STAT */
+		bd->bd_status = 0;
+
+		/* BD BUFFER ADDRESS */
+		bd->bd_addr = dma_buf + offset;
+
+		remaining -= rdesc->xfer_len;
+		offset += rdesc->xfer_len;
+	}
+
+	return 0;
+}
+
+static int pic32_sqi_prepare_hardware(struct spi_master *master)
+{
+	struct pic32_sqi *sqi = spi_master_get_devdata(master);
+
+	/* enable spi interface */
+	pic32_setbits(sqi->regs + PESQI_CONF_REG, PESQI_EN);
+	/* enable spi clk */
+	pic32_setbits(sqi->regs + PESQI_CLK_CTRL_REG, PESQI_CLK_EN);
+
+	return 0;
+}
+
+static int pic32_sqi_one_message(struct spi_master *master,
+				 struct spi_message *msg)
+{
+	struct spi_device *spi = msg->spi;
+	struct ring_desc *rdesc, *next;
+	struct spi_transfer *xfer;
+	struct pic32_sqi *sqi;
+	int ret = 0, mode;
+	u32 val;
+
+	sqi = spi_master_get_devdata(master);
+
+	reinit_completion(&sqi->xfer_done);
+	msg->actual_length = 0;
+
+	/* We can't handle spi_transfer specific "speed_hz", "bits_per_word"
+	 * and "delay_usecs". But spi_device specific speed and mode change
+	 * can be handled at best during spi chip-select switch.
+	 */
+	if (sqi->cur_spi != spi) {
+		/* set spi speed */
+		if (sqi->cur_speed != spi->max_speed_hz) {
+			sqi->cur_speed = spi->max_speed_hz;
+			ret = pic32_sqi_set_clk_rate(sqi, spi->max_speed_hz);
+			if (ret)
+				dev_warn(&spi->dev, "set_clk, %d\n", ret);
+		}
+
+		/* set spi mode */
+		mode = spi->mode & (SPI_MODE_3 | SPI_LSB_FIRST);
+		if (sqi->cur_mode != mode) {
+			val = readl(sqi->regs + PESQI_CONF_REG);
+			val &= ~(PESQI_CPOL | PESQI_CPHA | PESQI_LSBF);
+			if (mode & SPI_CPOL)
+				val |= PESQI_CPOL;
+			if (mode & SPI_LSB_FIRST)
+				val |= PESQI_LSBF;
+			val |= PESQI_CPHA;
+			writel(val, sqi->regs + PESQI_CONF_REG);
+
+			sqi->cur_mode = mode;
+		}
+		sqi->cur_spi = spi;
+	}
+
+	/* prepare hardware desc-list(BD) for transfer(s) */
+	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+		ret = pic32_sqi_one_transfer(sqi, msg, xfer);
+		if (ret) {
+			dev_err(&spi->dev, "xfer %p err\n", xfer);
+			goto xfer_out;
+		}
+	}
+
+	/* BDs are prepared and chained. Now mark LAST_BD, CS_DEASSERT at last
+	 * element of the list.
+	 */
+	rdesc = list_last_entry(&sqi->bd_list_used, struct ring_desc, list);
+	rdesc->bd->bd_ctrl |= BD_LAST | BD_CS_DEASSERT |
+			      BD_LIFM | BD_PKT_INT_EN;
+
+	/* set base address BD list for DMA engine */
+	rdesc = list_first_entry(&sqi->bd_list_used, struct ring_desc, list);
+	writel(rdesc->bd_dma, sqi->regs + PESQI_BD_BASE_ADDR_REG);
+
+	/* enable interrupt */
+	pic32_sqi_enable_int(sqi);
+
+	/* enable DMA engine */
+	val = PESQI_DMA_EN | PESQI_POLL_EN | PESQI_BDP_START;
+	writel(val, sqi->regs + PESQI_BD_CTRL_REG);
+
+	/* wait for xfer completion */
+	ret = wait_for_completion_timeout(&sqi->xfer_done, 5 * HZ);
+	if (ret <= 0) {
+		dev_err(&sqi->master->dev, "wait timedout/interrupted\n");
+		ret = -EIO;
+		msg->status = ret;
+	} else {
+		/* success */
+		msg->status = 0;
+		ret = 0;
+	}
+
+	/* disable DMA */
+	writel(0, sqi->regs + PESQI_BD_CTRL_REG);
+
+	pic32_sqi_disable_int(sqi);
+
+xfer_out:
+	/* unmap dma memory */
+	list_for_each_entry_reverse(xfer, &msg->transfers, transfer_list)
+		pic32_sqi_unmap_transfer(sqi, xfer);
+
+	list_for_each_entry_safe_reverse(rdesc, next,
+					 &sqi->bd_list_used, list) {
+		/* Update total byte transferred */
+		msg->actual_length += rdesc->xfer_len;
+		/* release ring descr */
+		ring_desc_put(sqi, rdesc);
+	}
+	spi_finalize_current_message(spi->master);
+
+	return ret;
+}
+
+static int pic32_sqi_unprepare_hardware(struct spi_master *master)
+{
+	struct pic32_sqi *sqi = spi_master_get_devdata(master);
+
+	/* disable clk */
+	pic32_clrbits(sqi->regs + PESQI_CLK_CTRL_REG, PESQI_CLK_EN);
+	/* disable spi */
+	pic32_clrbits(sqi->regs + PESQI_CONF_REG, PESQI_EN);
+
+	return 0;
+}
+
+/* This may be called twice for each spi dev */
+static int pic32_sqi_setup(struct spi_device *spi)
+{
+	struct pic32_sqi *sqi;
+
+	if (spi_get_ctldata(spi)) {
+		dev_err(&spi->dev, "is already associated\n");
+		return -EBUSY;
+	}
+
+	/* check word size */
+	if (!spi->bits_per_word) {
+		dev_err(&spi->dev, "No bits_per_word defined\n");
+		return -EINVAL;
+	}
+
+	/* check maximum SPI clk rate */
+	if (!spi->max_speed_hz) {
+		dev_err(&spi->dev, "No max speed HZ parameter\n");
+		return -EINVAL;
+	}
+
+	if (spi->master->max_speed_hz < spi->max_speed_hz) {
+		dev_err(&spi->dev, "max speed %u HZ is too high\n",
+			spi->max_speed_hz);
+		return -EINVAL;
+	}
+
+	sqi = spi_master_get_devdata(spi->master);
+	spi_set_ctldata(spi, (void *)sqi);
+
+	return 0;
+}
+
+static void pic32_sqi_cleanup(struct spi_device *spi)
+{
+	spi_set_ctldata(spi, (void *)NULL);
+}
+
+static int ring_desc_ring_alloc(struct pic32_sqi *sqi)
+{
+	struct ring_desc *rdesc;
+	struct buf_desc *bd;
+	int i;
+
+	/* allocate coherent memory for hardware buffer descriptors. */
+	sqi->bd = dma_zalloc_coherent(&sqi->master->dev,
+				      sizeof(*bd) * PESQI_BD_COUNT,
+				      &sqi->bd_dma, GFP_DMA32);
+	if (!sqi->bd) {
+		dev_err(&sqi->master->dev, "failed allocating dma buffer\n");
+		return -ENOMEM;
+	}
+
+	/* allocate software ring descriptors */
+	sqi->ring = devm_kcalloc(&sqi->master->dev, PESQI_BD_COUNT,
+				 sizeof(*rdesc), GFP_KERNEL);
+	if (!sqi->ring) {
+		dma_free_coherent(&sqi->master->dev,
+				  sizeof(*bd) * PESQI_BD_COUNT,
+				  sqi->bd, sqi->bd_dma);
+		return -ENOMEM;
+	}
+
+	bd = (struct buf_desc *)sqi->bd;
+
+	INIT_LIST_HEAD(&sqi->bd_list_free);
+	INIT_LIST_HEAD(&sqi->bd_list_used);
+
+	/* initialize ring-desc */
+	for (i = 0, rdesc = sqi->ring; i < PESQI_BD_COUNT; i++, rdesc++) {
+		INIT_LIST_HEAD(&rdesc->list);
+		rdesc->bd = &bd[i];
+		rdesc->bd_dma = sqi->bd_dma + (void *)&bd[i] - (void *)bd;
+		list_add_tail(&rdesc->list, &sqi->bd_list_free);
+	}
+
+	/* Prepare BD: chain to next BD(s) */
+	for (i = 0, rdesc = sqi->ring; i < PESQI_BD_COUNT; i++)
+		bd[i].bd_nextp = rdesc[i + 1].bd_dma;
+	bd[PESQI_BD_COUNT - 1].bd_nextp = 0;
+
+	return 0;
+}
+
+static void ring_desc_ring_free(struct pic32_sqi *sqi)
+{
+	dma_free_coherent(&sqi->master->dev,
+			  sizeof(struct buf_desc) * PESQI_BD_COUNT,
+			  sqi->bd, sqi->bd_dma);
+}
+
+static void pic32_sqi_hw_init(struct pic32_sqi *sqi)
+{
+	unsigned long flags;
+	u32 val;
+
+	/* Soft-reset of PESQI controller triggers interrupt.
+	 * We are not yet ready to handle them so disable CPU
+	 * interrupt for the time being.
+	 */
+	local_irq_save(flags);
+
+	/* assert soft-reset */
+	writel(PESQI_SOFT_RESET, sqi->regs + PESQI_CONF_REG);
+
+	/* wait until clear */
+	readl_poll_timeout_atomic(sqi->regs + PESQI_CONF_REG, val,
+				  !(val & PESQI_SOFT_RESET), 1, 5000);
+
+	/* disable all interrupts */
+	pic32_sqi_disable_int(sqi);
+
+	/* Now it is safe to enable back CPU interrupt */
+	local_irq_restore(flags);
+
+	/* tx and rx fifo interrupt threshold */
+	val = readl(sqi->regs + PESQI_CMD_THRES_REG);
+	val &= ~(PESQI_TXTHR_MASK << PESQI_TXTHR_SHIFT);
+	val &= ~(PESQI_RXTHR_MASK << PESQI_RXTHR_SHIFT);
+	val |= (1U << PESQI_TXTHR_SHIFT) | (1U << PESQI_RXTHR_SHIFT);
+	writel(val, sqi->regs + PESQI_CMD_THRES_REG);
+
+	val = readl(sqi->regs + PESQI_INT_THRES_REG);
+	val &= ~(PESQI_TXTHR_MASK << PESQI_TXTHR_SHIFT);
+	val &= ~(PESQI_RXTHR_MASK << PESQI_RXTHR_SHIFT);
+	val |= (1U << PESQI_TXTHR_SHIFT) | (1U << PESQI_RXTHR_SHIFT);
+	writel(val, sqi->regs + PESQI_INT_THRES_REG);
+
+	/* default configuration */
+	val = readl(sqi->regs + PESQI_CONF_REG);
+
+	/* set mode: DMA */
+	val &= ~PESQI_MODE;
+	val |= PESQI_MODE_DMA << PESQI_MODE_SHIFT;
+	writel(val, sqi->regs + PESQI_CONF_REG);
+
+	/* DATAEN - SQIID0-ID3 */
+	val |= PESQI_QUAD_LANE << PESQI_LANES_SHIFT;
+
+	/* burst/INCR4 enable */
+	val |= PESQI_BURST_EN;
+
+	/* CSEN - all CS */
+	val |= 3U << PESQI_CSEN_SHIFT;
+	writel(val, sqi->regs + PESQI_CONF_REG);
+
+	/* write poll count */
+	writel(0, sqi->regs + PESQI_BD_POLL_CTRL_REG);
+
+	sqi->cur_speed = 0;
+	sqi->cur_mode = -1;
+}
+
+static int pic32_sqi_probe(struct platform_device *pdev)
+{
+	struct spi_master *master;
+	struct pic32_sqi *sqi;
+	struct resource *reg;
+	int ret;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*sqi));
+	if (!master)
+		return -ENOMEM;
+
+	sqi = spi_master_get_devdata(master);
+	sqi->master = master;
+
+	reg = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	sqi->regs = devm_ioremap_resource(&pdev->dev, reg);
+	if (!sqi->regs) {
+		dev_err(&pdev->dev, "mem map failed\n");
+		ret = -EBUSY;
+		goto err_free_master;
+	}
+
+	/* irq resource */
+	sqi->irq = platform_get_irq(pdev, 0);
+	if (sqi->irq < 0) {
+		dev_err(&pdev->dev, "no irq found\n");
+		ret = sqi->irq;
+		goto err_free_master;
+	}
+
+	/* clock */
+	sqi->sys_clk = devm_clk_get(&pdev->dev, "reg_ck");
+	if (IS_ERR(sqi->sys_clk)) {
+		ret = PTR_ERR(sqi->sys_clk);
+		dev_err(&pdev->dev, "no sys_clk ?\n");
+		goto err_free_master;
+	}
+
+	sqi->base_clk = devm_clk_get(&pdev->dev, "spi_ck");
+	if (IS_ERR(sqi->base_clk)) {
+		ret = PTR_ERR(sqi->base_clk);
+		dev_err(&pdev->dev, "no base clk ?\n");
+		goto err_free_master;
+	}
+
+	clk_prepare_enable(sqi->sys_clk);
+	clk_prepare_enable(sqi->base_clk);
+
+	init_completion(&sqi->xfer_done);
+
+	/* initialize hardware */
+	pic32_sqi_hw_init(sqi);
+
+	/* allocate buffers & descriptors */
+	ret = ring_desc_ring_alloc(sqi);
+	if (ret) {
+		dev_err(&pdev->dev, "ring alloc failed\n");
+		goto err_disable_hw;
+	}
+
+	/* install irq handlers */
+	ret = devm_request_irq(&pdev->dev, sqi->irq, pic32_sqi_isr,
+			       0, dev_name(&pdev->dev), sqi);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "request-irq %d, failed ?\n", sqi->irq);
+		goto err_free_ring;
+	}
+
+	/* register master */
+	master->num_chipselect	= 2;
+	master->max_speed_hz	= clk_get_rate(sqi->base_clk);
+	master->dma_alignment	= 32;
+	master->dev.of_node	= of_node_get(pdev->dev.of_node);
+	master->mode_bits	= SPI_MODE_3 | SPI_MODE_0 | SPI_TX_DUAL |
+				  SPI_RX_DUAL | SPI_TX_QUAD | SPI_RX_QUAD;
+	master->flags		= SPI_MASTER_HALF_DUPLEX;
+	master->setup		= pic32_sqi_setup;
+	master->cleanup		= pic32_sqi_cleanup;
+	master->bits_per_word_mask	= SPI_BPW_RANGE_MASK(8, 32);
+	master->transfer_one_message	= pic32_sqi_one_message;
+	master->prepare_transfer_hardware	= pic32_sqi_prepare_hardware;
+	master->unprepare_transfer_hardware	= pic32_sqi_unprepare_hardware;
+
+	ret = devm_spi_register_master(&pdev->dev, master);
+	if (ret) {
+		dev_err(&master->dev, "failed registering spi master\n");
+		goto err_free_ring;
+	}
+
+	platform_set_drvdata(pdev, sqi);
+
+	return 0;
+
+err_free_ring:
+	ring_desc_ring_free(sqi);
+err_disable_hw:
+	/* disable clk */
+	clk_disable_unprepare(sqi->base_clk);
+	clk_disable_unprepare(sqi->sys_clk);
+err_free_master:
+	spi_master_put(master);
+	return ret;
+}
+
+static int pic32_sqi_remove(struct platform_device *pdev)
+{
+	struct pic32_sqi *sqi = platform_get_drvdata(pdev);
+
+	clk_disable_unprepare(sqi->base_clk);
+	clk_disable_unprepare(sqi->sys_clk);
+
+	/* release memory */
+	ring_desc_ring_free(sqi);
+
+	return 0;
+}
+
+static const struct of_device_id pic32_sqi_of_ids[] = {
+	{.compatible = "microchip,pic32mzda-sqi",},
+	{},
+};
+MODULE_DEVICE_TABLE(of, pic32_sqi_of_ids);
+
+static struct platform_driver pic32_sqi_driver = {
+	.driver = {
+		.name = "sqi-pic32",
+		.of_match_table = of_match_ptr(pic32_sqi_of_ids),
+	},
+	.probe = pic32_sqi_probe,
+	.remove = pic32_sqi_remove,
+};
+
+module_platform_driver(pic32_sqi_driver);
+
+MODULE_AUTHOR("Purna Chandra Mandal <purna.mandal@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Microchip SPI driver for PIC32 SQI controller.");
+MODULE_LICENSE("GPL v2");
-- 
1.8.3.1

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