spi: add support for DLN-2 USB-SPI adapter

This adds support for Diolan DLN2 USB-SPI adapter.

Information about the USB protocol interface can be found in the
Programmer's Reference Manual [1], see section 5.4.6 for the SPI
master module commands and responses.

[1] https://www.diolan.com/downloads/dln-api-manual.pdf

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 890 insertions, 0 deletions

diff --git a/drivers/spi/spi-dln2.c b/drivers/spi/spi-dln2.c
new file mode 100644
index 000000000000..7b3545469469
--- /dev/null
+++ b/drivers/spi/spi-dln2.c
@@ -0,0 +1,890 @@
+/*
+ * Driver for the Diolan DLN-2 USB-SPI adapter
+ *
+ * Copyright (c) 2014 Intel Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/dln2.h>
+#include <linux/spi/spi.h>
+#include <linux/pm_runtime.h>
+#include <asm/unaligned.h>
+
+#define DLN2_SPI_MODULE_ID              0x02
+#define DLN2_SPI_CMD(cmd)               DLN2_CMD(cmd, DLN2_SPI_MODULE_ID)
+
+/* SPI commands */
+#define DLN2_SPI_GET_PORT_COUNT                 DLN2_SPI_CMD(0x00)
+#define DLN2_SPI_ENABLE                         DLN2_SPI_CMD(0x11)
+#define DLN2_SPI_DISABLE                        DLN2_SPI_CMD(0x12)
+#define DLN2_SPI_IS_ENABLED                     DLN2_SPI_CMD(0x13)
+#define DLN2_SPI_SET_MODE                       DLN2_SPI_CMD(0x14)
+#define DLN2_SPI_GET_MODE                       DLN2_SPI_CMD(0x15)
+#define DLN2_SPI_SET_FRAME_SIZE                 DLN2_SPI_CMD(0x16)
+#define DLN2_SPI_GET_FRAME_SIZE                 DLN2_SPI_CMD(0x17)
+#define DLN2_SPI_SET_FREQUENCY                  DLN2_SPI_CMD(0x18)
+#define DLN2_SPI_GET_FREQUENCY                  DLN2_SPI_CMD(0x19)
+#define DLN2_SPI_READ_WRITE                     DLN2_SPI_CMD(0x1A)
+#define DLN2_SPI_READ                           DLN2_SPI_CMD(0x1B)
+#define DLN2_SPI_WRITE                          DLN2_SPI_CMD(0x1C)
+#define DLN2_SPI_SET_DELAY_BETWEEN_SS           DLN2_SPI_CMD(0x20)
+#define DLN2_SPI_GET_DELAY_BETWEEN_SS           DLN2_SPI_CMD(0x21)
+#define DLN2_SPI_SET_DELAY_AFTER_SS             DLN2_SPI_CMD(0x22)
+#define DLN2_SPI_GET_DELAY_AFTER_SS             DLN2_SPI_CMD(0x23)
+#define DLN2_SPI_SET_DELAY_BETWEEN_FRAMES       DLN2_SPI_CMD(0x24)
+#define DLN2_SPI_GET_DELAY_BETWEEN_FRAMES       DLN2_SPI_CMD(0x25)
+#define DLN2_SPI_SET_SS                         DLN2_SPI_CMD(0x26)
+#define DLN2_SPI_GET_SS                         DLN2_SPI_CMD(0x27)
+#define DLN2_SPI_RELEASE_SS                     DLN2_SPI_CMD(0x28)
+#define DLN2_SPI_SS_VARIABLE_ENABLE             DLN2_SPI_CMD(0x2B)
+#define DLN2_SPI_SS_VARIABLE_DISABLE            DLN2_SPI_CMD(0x2C)
+#define DLN2_SPI_SS_VARIABLE_IS_ENABLED         DLN2_SPI_CMD(0x2D)
+#define DLN2_SPI_SS_AAT_ENABLE                  DLN2_SPI_CMD(0x2E)
+#define DLN2_SPI_SS_AAT_DISABLE                 DLN2_SPI_CMD(0x2F)
+#define DLN2_SPI_SS_AAT_IS_ENABLED              DLN2_SPI_CMD(0x30)
+#define DLN2_SPI_SS_BETWEEN_FRAMES_ENABLE       DLN2_SPI_CMD(0x31)
+#define DLN2_SPI_SS_BETWEEN_FRAMES_DISABLE      DLN2_SPI_CMD(0x32)
+#define DLN2_SPI_SS_BETWEEN_FRAMES_IS_ENABLED   DLN2_SPI_CMD(0x33)
+#define DLN2_SPI_SET_CPHA                       DLN2_SPI_CMD(0x34)
+#define DLN2_SPI_GET_CPHA                       DLN2_SPI_CMD(0x35)
+#define DLN2_SPI_SET_CPOL                       DLN2_SPI_CMD(0x36)
+#define DLN2_SPI_GET_CPOL                       DLN2_SPI_CMD(0x37)
+#define DLN2_SPI_SS_MULTI_ENABLE                DLN2_SPI_CMD(0x38)
+#define DLN2_SPI_SS_MULTI_DISABLE               DLN2_SPI_CMD(0x39)
+#define DLN2_SPI_SS_MULTI_IS_ENABLED            DLN2_SPI_CMD(0x3A)
+#define DLN2_SPI_GET_SUPPORTED_MODES            DLN2_SPI_CMD(0x40)
+#define DLN2_SPI_GET_SUPPORTED_CPHA_VALUES      DLN2_SPI_CMD(0x41)
+#define DLN2_SPI_GET_SUPPORTED_CPOL_VALUES      DLN2_SPI_CMD(0x42)
+#define DLN2_SPI_GET_SUPPORTED_FRAME_SIZES      DLN2_SPI_CMD(0x43)
+#define DLN2_SPI_GET_SS_COUNT                   DLN2_SPI_CMD(0x44)
+#define DLN2_SPI_GET_MIN_FREQUENCY              DLN2_SPI_CMD(0x45)
+#define DLN2_SPI_GET_MAX_FREQUENCY              DLN2_SPI_CMD(0x46)
+#define DLN2_SPI_GET_MIN_DELAY_BETWEEN_SS       DLN2_SPI_CMD(0x47)
+#define DLN2_SPI_GET_MAX_DELAY_BETWEEN_SS       DLN2_SPI_CMD(0x48)
+#define DLN2_SPI_GET_MIN_DELAY_AFTER_SS         DLN2_SPI_CMD(0x49)
+#define DLN2_SPI_GET_MAX_DELAY_AFTER_SS         DLN2_SPI_CMD(0x4A)
+#define DLN2_SPI_GET_MIN_DELAY_BETWEEN_FRAMES   DLN2_SPI_CMD(0x4B)
+#define DLN2_SPI_GET_MAX_DELAY_BETWEEN_FRAMES   DLN2_SPI_CMD(0x4C)
+
+#define DLN2_SPI_MAX_XFER_SIZE                  256
+#define DLN2_SPI_BUF_SIZE                       (DLN2_SPI_MAX_XFER_SIZE + 16)
+#define DLN2_SPI_ATTR_LEAVE_SS_LOW              BIT(0)
+#define DLN2_TRANSFERS_WAIT_COMPLETE            1
+#define DLN2_TRANSFERS_CANCEL                   0
+#define DLN2_RPM_AUTOSUSPEND_TIMEOUT            2000
+
+struct dln2_spi {
+        struct platform_device *pdev;
+        struct spi_master *master;
+        u8 port;
+
+        /*
+         * This buffer will be used mainly for read/write operations. Since
+         * they're quite large, we cannot use the stack. Protection is not
+         * needed because all SPI communication is serialized by the SPI core.
+         */
+        void *buf;
+
+        u8 bpw;
+        u32 speed;
+        u16 mode;
+        u8 cs;
+};
+
+/*
+ * Enable/Disable SPI module. The disable command will wait for transfers to
+ * complete first.
+ */
+static int dln2_spi_enable(struct dln2_spi *dln2, bool enable)
+{
+        int ret;
+        u16 cmd;
+        struct {
+                u8 port;
+                u8 wait_for_completion;
+        } tx;
+        unsigned len = sizeof(tx);
+
+        tx.port = dln2->port;
+
+        if (enable) {
+                cmd = DLN2_SPI_ENABLE;
+                len -= sizeof(tx.wait_for_completion);
+        } else {
+                tx.wait_for_completion = DLN2_TRANSFERS_WAIT_COMPLETE;
+                cmd = DLN2_SPI_DISABLE;
+        }
+
+        ret = dln2_transfer_tx(dln2->pdev, cmd, &tx, len);
+        if (ret < 0)
+                return ret;
+
+        return 0;
+}
+
+/*
+ * Select/unselect multiple CS lines. The selected lines will be automatically
+ * toggled LOW/HIGH by the board firmware during transfers, provided they're
+ * enabled first.
+ *
+ * Ex: cs_mask = 0x03 -> CS0 & CS1 will be selected and the next WR/RD operation
+ *                       will toggle the lines LOW/HIGH automatically.
+ */
+static int dln2_spi_cs_set(struct dln2_spi *dln2, u8 cs_mask)
+{
+        struct {
+                u8 port;
+                u8 cs;
+        } tx;
+
+        tx.port = dln2->port;
+
+        /*
+         * According to Diolan docs, "a slave device can be selected by changing
+         * the corresponding bit value to 0". The rest must be set to 1. Hence
+         * the bitwise NOT in front.
+         */
+        tx.cs = ~cs_mask;
+
+        return dln2_transfer_tx(dln2->pdev, DLN2_SPI_SET_SS, &tx, sizeof(tx));
+}
+
+/*
+ * Select one CS line. The other lines will be un-selected.
+ */
+static int dln2_spi_cs_set_one(struct dln2_spi *dln2, u8 cs)
+{
+        return dln2_spi_cs_set(dln2, BIT(cs));
+}
+
+/*
+ * Enable/disable CS lines for usage. The module has to be disabled first.
+ */
+static int dln2_spi_cs_enable(struct dln2_spi *dln2, u8 cs_mask, bool enable)
+{
+        struct {
+                u8 port;
+                u8 cs;
+        } tx;
+        u16 cmd;
+
+        tx.port = dln2->port;
+        tx.cs = cs_mask;
+        cmd = enable ? DLN2_SPI_SS_MULTI_ENABLE : DLN2_SPI_SS_MULTI_DISABLE;
+
+        return dln2_transfer_tx(dln2->pdev, cmd, &tx, sizeof(tx));
+}
+
+static int dln2_spi_cs_enable_all(struct dln2_spi *dln2, bool enable)
+{
+        u8 cs_mask = GENMASK(dln2->master->num_chipselect - 1, 0);
+
+        return dln2_spi_cs_enable(dln2, cs_mask, enable);
+}
+
+static int dln2_spi_get_cs_num(struct dln2_spi *dln2, u16 *cs_num)
+{
+        int ret;
+        struct {
+                u8 port;
+        } tx;
+        struct {
+                __le16 cs_count;
+        } rx;
+        unsigned rx_len = sizeof(rx);
+
+        tx.port = dln2->port;
+        ret = dln2_transfer(dln2->pdev, DLN2_SPI_GET_SS_COUNT, &tx, sizeof(tx),
+                            &rx, &rx_len);
+        if (ret < 0)
+                return ret;
+        if (rx_len < sizeof(rx))
+                return -EPROTO;
+
+        *cs_num = le16_to_cpu(rx.cs_count);
+
+        dev_dbg(&dln2->pdev->dev, "cs_num = %d\n", *cs_num);
+
+        return 0;
+}
+
+static int dln2_spi_get_speed(struct dln2_spi *dln2, u16 cmd, u32 *freq)
+{
+        int ret;
+        struct {
+                u8 port;
+        } tx;
+        struct {
+                __le32 speed;
+        } rx;
+        unsigned rx_len = sizeof(rx);
+
+        tx.port = dln2->port;
+
+        ret = dln2_transfer(dln2->pdev, cmd, &tx, sizeof(tx), &rx, &rx_len);
+        if (ret < 0)
+                return ret;
+        if (rx_len < sizeof(rx))
+                return -EPROTO;
+
+        *freq = le32_to_cpu(rx.speed);
+
+        return 0;
+}
+
+/*
+ * Get bus min/max frequencies.
+ */
+static int dln2_spi_get_speed_range(struct dln2_spi *dln2, u32 *fmin, u32 *fmax)
+{
+        int ret;
+
+        ret = dln2_spi_get_speed(dln2, DLN2_SPI_GET_MIN_FREQUENCY, fmin);
+        if (ret < 0)
+                return ret;
+
+        ret = dln2_spi_get_speed(dln2, DLN2_SPI_GET_MAX_FREQUENCY, fmax);
+        if (ret < 0)
+                return ret;
+
+        dev_dbg(&dln2->pdev->dev, "freq_min = %d, freq_max = %d\n",
+                *fmin, *fmax);
+
+        return 0;
+}
+
+/*
+ * Set the bus speed. The module will automatically round down to the closest
+ * available frequency and returns it. The module has to be disabled first.
+ */
+static int dln2_spi_set_speed(struct dln2_spi *dln2, u32 speed)
+{
+        int ret;
+        struct {
+                u8 port;
+                __le32 speed;
+        } __packed tx;
+        struct {
+                __le32 speed;
+        } rx;
+        int rx_len = sizeof(rx);
+
+        tx.port = dln2->port;
+        tx.speed = cpu_to_le32(speed);
+
+        ret = dln2_transfer(dln2->pdev, DLN2_SPI_SET_FREQUENCY, &tx, sizeof(tx),
+                            &rx, &rx_len);
+        if (ret < 0)
+                return ret;
+        if (rx_len < sizeof(rx))
+                return -EPROTO;
+
+        return 0;
+}
+
+/*
+ * Change CPOL & CPHA. The module has to be disabled first.
+ */
+static int dln2_spi_set_mode(struct dln2_spi *dln2, u8 mode)
+{
+        struct {
+                u8 port;
+                u8 mode;
+        } tx;
+
+        tx.port = dln2->port;
+        tx.mode = mode;
+
+        return dln2_transfer_tx(dln2->pdev, DLN2_SPI_SET_MODE, &tx, sizeof(tx));
+}
+
+/*
+ * Change frame size. The module has to be disabled first.
+ */
+static int dln2_spi_set_bpw(struct dln2_spi *dln2, u8 bpw)
+{
+        struct {
+                u8 port;
+                u8 bpw;
+        } tx;
+
+        tx.port = dln2->port;
+        tx.bpw = bpw;
+
+        return dln2_transfer_tx(dln2->pdev, DLN2_SPI_SET_FRAME_SIZE,
+                                &tx, sizeof(tx));
+}
+
+static int dln2_spi_get_supported_frame_sizes(struct dln2_spi *dln2,
+                                              u32 *bpw_mask)
+{
+        int ret;
+        struct {
+                u8 port;
+        } tx;
+        struct {
+                u8 count;
+                u8 frame_sizes[36];
+        } *rx = dln2->buf;
+        unsigned rx_len = sizeof(*rx);
+        int i;
+
+        tx.port = dln2->port;
+
+        ret = dln2_transfer(dln2->pdev, DLN2_SPI_GET_SUPPORTED_FRAME_SIZES,
+                            &tx, sizeof(tx), rx, &rx_len);
+        if (ret < 0)
+                return ret;
+        if (rx_len < sizeof(*rx))
+                return -EPROTO;
+        if (rx->count > ARRAY_SIZE(rx->frame_sizes))
+                return -EPROTO;
+
+        *bpw_mask = 0;
+        for (i = 0; i < rx->count; i++)
+                *bpw_mask |= BIT(rx->frame_sizes[i] - 1);
+
+        dev_dbg(&dln2->pdev->dev, "bpw_mask = 0x%X\n", *bpw_mask);
+
+        return 0;
+}
+
+/*
+ * Copy the data to DLN2 buffer and change the byte order to LE, requested by
+ * DLN2 module. SPI core makes sure that the data length is a multiple of word
+ * size.
+ */
+static int dln2_spi_copy_to_buf(u8 *dln2_buf, const u8 *src, u16 len, u8 bpw)
+{
+#ifdef __LITTLE_ENDIAN
+        memcpy(dln2_buf, src, len);
+#else
+        if (bpw <= 8) {
+                memcpy(dln2_buf, src, len);
+        } else if (bpw <= 16) {
+                __le16 *d = (__le16 *)dln2_buf;
+                u16 *s = (u16 *)src;
+
+                len = len / 2;
+                while (len--)
+                        *d++ = cpu_to_le16p(s++);
+        } else {
+                __le32 *d = (__le32 *)dln2_buf;
+                u32 *s = (u32 *)src;
+
+                len = len / 4;
+                while (len--)
+                        *d++ = cpu_to_le32p(s++);
+        }
+#endif
+
+        return 0;
+}
+
+/*
+ * Copy the data from DLN2 buffer and convert to CPU byte order since the DLN2
+ * buffer is LE ordered. SPI core makes sure that the data length is a multiple
+ * of word size. The RX dln2_buf is 2 byte aligned so, for BE, we have to make
+ * sure we avoid unaligned accesses for 32 bit case.
+ */
+static int dln2_spi_copy_from_buf(u8 *dest, const u8 *dln2_buf, u16 len, u8 bpw)
+{
+#ifdef __LITTLE_ENDIAN
+        memcpy(dest, dln2_buf, len);
+#else
+        if (bpw <= 8) {
+                memcpy(dest, dln2_buf, len);
+        } else if (bpw <= 16) {
+                u16 *d = (u16 *)dest;
+                __le16 *s = (__le16 *)dln2_buf;
+
+                len = len / 2;
+                while (len--)
+                        *d++ = le16_to_cpup(s++);
+        } else {
+                u32 *d = (u32 *)dest;
+                __le32 *s = (__le32 *)dln2_buf;
+
+                len = len / 4;
+                while (len--)
+                        *d++ = get_unaligned_le32(s++);
+        }
+#endif
+
+        return 0;
+}
+
+/*
+ * Perform one write operation.
+ */
+static int dln2_spi_write_one(struct dln2_spi *dln2, const u8 *data,
+                              u16 data_len, u8 attr)
+{
+        struct {
+                u8 port;
+                __le16 size;
+                u8 attr;
+                u8 buf[DLN2_SPI_MAX_XFER_SIZE];
+        } __packed *tx = dln2->buf;
+        unsigned tx_len;
+
+        BUILD_BUG_ON(sizeof(*tx) > DLN2_SPI_BUF_SIZE);
+
+        if (data_len > DLN2_SPI_MAX_XFER_SIZE)
+                return -EINVAL;
+
+        tx->port = dln2->port;
+        tx->size = cpu_to_le16(data_len);
+        tx->attr = attr;
+
+        dln2_spi_copy_to_buf(tx->buf, data, data_len, dln2->bpw);
+
+        tx_len = sizeof(*tx) + data_len - DLN2_SPI_MAX_XFER_SIZE;
+        return dln2_transfer_tx(dln2->pdev, DLN2_SPI_WRITE, tx, tx_len);
+}
+
+/*
+ * Perform one read operation.
+ */
+static int dln2_spi_read_one(struct dln2_spi *dln2, u8 *data,
+                             u16 data_len, u8 attr)
+{
+        int ret;
+        struct {
+                u8 port;
+                __le16 size;
+                u8 attr;
+        } __packed tx;
+        struct {
+                __le16 size;
+                u8 buf[DLN2_SPI_MAX_XFER_SIZE];
+        } __packed *rx = dln2->buf;
+        unsigned rx_len = sizeof(*rx);
+
+        BUILD_BUG_ON(sizeof(*rx) > DLN2_SPI_BUF_SIZE);
+
+        if (data_len > DLN2_SPI_MAX_XFER_SIZE)
+                return -EINVAL;
+
+        tx.port = dln2->port;
+        tx.size = cpu_to_le16(data_len);
+        tx.attr = attr;
+
+        ret = dln2_transfer(dln2->pdev, DLN2_SPI_READ, &tx, sizeof(tx),
+                            rx, &rx_len);
+        if (ret < 0)
+                return ret;
+        if (rx_len < sizeof(rx->size) + data_len)
+                return -EPROTO;
+        if (le16_to_cpu(rx->size) != data_len)
+                return -EPROTO;
+
+        dln2_spi_copy_from_buf(data, rx->buf, data_len, dln2->bpw);
+
+        return 0;
+}
+
+/*
+ * Perform one write & read operation.
+ */
+static int dln2_spi_read_write_one(struct dln2_spi *dln2, const u8 *tx_data,
+                                   u8 *rx_data, u16 data_len, u8 attr)
+{
+        int ret;
+        struct {
+                u8 port;
+                __le16 size;
+                u8 attr;
+                u8 buf[DLN2_SPI_MAX_XFER_SIZE];
+        } __packed *tx;
+        struct {
+                __le16 size;
+                u8 buf[DLN2_SPI_MAX_XFER_SIZE];
+        } __packed *rx;
+        unsigned tx_len, rx_len;
+
+        BUILD_BUG_ON(sizeof(*tx) > DLN2_SPI_BUF_SIZE ||
+                     sizeof(*rx) > DLN2_SPI_BUF_SIZE);
+
+        if (data_len > DLN2_SPI_MAX_XFER_SIZE)
+                return -EINVAL;
+
+        /*
+         * Since this is a pseudo full-duplex communication, we're perfectly
+         * safe to use the same buffer for both tx and rx. When DLN2 sends the
+         * response back, with the rx data, we don't need the tx buffer anymore.
+         */
+        tx = dln2->buf;
+        rx = dln2->buf;
+
+        tx->port = dln2->port;
+        tx->size = cpu_to_le16(data_len);
+        tx->attr = attr;
+
+        dln2_spi_copy_to_buf(tx->buf, tx_data, data_len, dln2->bpw);
+
+        tx_len = sizeof(*tx) + data_len - DLN2_SPI_MAX_XFER_SIZE;
+        rx_len = sizeof(*rx);
+
+        ret = dln2_transfer(dln2->pdev, DLN2_SPI_READ_WRITE, tx, tx_len,
+                            rx, &rx_len);
+        if (ret < 0)
+                return ret;
+        if (rx_len < sizeof(rx->size) + data_len)
+                return -EPROTO;
+        if (le16_to_cpu(rx->size) != data_len)
+                return -EPROTO;
+
+        dln2_spi_copy_from_buf(rx_data, rx->buf, data_len, dln2->bpw);
+
+        return 0;
+}
+
+/*
+ * Read/Write wrapper. It will automatically split an operation into multiple
+ * single ones due to device buffer constraints.
+ */
+static int dln2_spi_rdwr(struct dln2_spi *dln2, const u8 *tx_data,
+                         u8 *rx_data, u16 data_len, u8 attr) {
+        int ret;
+        u16 len;
+        u8 temp_attr;
+        u16 remaining = data_len;
+        u16 offset;
+
+        do {
+                if (remaining > DLN2_SPI_MAX_XFER_SIZE) {
+                        len = DLN2_SPI_MAX_XFER_SIZE;
+                        temp_attr = DLN2_SPI_ATTR_LEAVE_SS_LOW;
+                } else {
+                        len = remaining;
+                        temp_attr = attr;
+                }
+
+                offset = data_len - remaining;
+
+                if (tx_data && rx_data) {
+                        ret = dln2_spi_read_write_one(dln2,
+                                                      tx_data + offset,
+                                                      rx_data + offset,
+                                                      len, temp_attr);
+                } else if (tx_data) {
+                        ret = dln2_spi_write_one(dln2,
+                                                 tx_data + offset,
+                                                 len, temp_attr);
+                } else if (rx_data) {
+                        ret = dln2_spi_read_one(dln2,
+                                                rx_data + offset,
+                                                len, temp_attr);
+                 } else {
+                        return -EINVAL;
+                 }
+
+                if (ret < 0)
+                        return ret;
+
+                remaining -= len;
+        } while (remaining);
+
+        return 0;
+}
+
+static int dln2_spi_prepare_message(struct spi_master *master,
+                                    struct spi_message *message)
+{
+        int ret;
+        struct dln2_spi *dln2 = spi_master_get_devdata(master);
+        struct spi_device *spi = message->spi;
+
+        if (dln2->cs != spi->chip_select) {
+                ret = dln2_spi_cs_set_one(dln2, spi->chip_select);
+                if (ret < 0)
+                        return ret;
+
+                dln2->cs = spi->chip_select;
+        }
+
+        return 0;
+}
+
+static int dln2_spi_transfer_setup(struct dln2_spi *dln2, u32 speed,
+                                   u8 bpw, u8 mode)
+{
+        int ret;
+        bool bus_setup_change;
+
+        bus_setup_change = dln2->speed != speed || dln2->mode != mode ||
+                           dln2->bpw != bpw;
+
+        if (!bus_setup_change)
+                return 0;
+
+        ret = dln2_spi_enable(dln2, false);
+        if (ret < 0)
+                return ret;
+
+        if (dln2->speed != speed) {
+                ret = dln2_spi_set_speed(dln2, speed);
+                if (ret < 0)
+                        return ret;
+
+                dln2->speed = speed;
+        }
+
+        if (dln2->mode != mode) {
+                ret = dln2_spi_set_mode(dln2, mode & 0x3);
+                if (ret < 0)
+                        return ret;
+
+                dln2->mode = mode;
+        }
+
+        if (dln2->bpw != bpw) {
+                ret = dln2_spi_set_bpw(dln2, bpw);
+                if (ret < 0)
+                        return ret;
+
+                dln2->bpw = bpw;
+        }
+
+        ret = dln2_spi_enable(dln2, true);
+        if (ret < 0)
+                return ret;
+
+        return 0;
+}
+
+static int dln2_spi_transfer_one(struct spi_master *master,
+                                 struct spi_device *spi,
+                                 struct spi_transfer *xfer)
+{
+        struct dln2_spi *dln2 = spi_master_get_devdata(master);
+        int status;
+        u8 attr = 0;
+
+        status = dln2_spi_transfer_setup(dln2, xfer->speed_hz,
+                                         xfer->bits_per_word,
+                                         spi->mode);
+        if (status < 0) {
+                dev_err(&dln2->pdev->dev, "Cannot setup transfer\n");
+                return status;
+        }
+
+        if (!xfer->cs_change && !spi_transfer_is_last(master, xfer))
+                attr = DLN2_SPI_ATTR_LEAVE_SS_LOW;
+
+        status = dln2_spi_rdwr(dln2, xfer->tx_buf, xfer->rx_buf,
+                               xfer->len, attr);
+        if (status < 0)
+                dev_err(&dln2->pdev->dev, "write/read failed!\n");
+
+        return status;
+}
+
+static int dln2_spi_probe(struct platform_device *pdev)
+{
+        struct spi_master *master;
+        struct dln2_spi *dln2;
+        struct dln2_platform_data *pdata = dev_get_platdata(&pdev->dev);
+        int ret;
+
+        master = spi_alloc_master(&pdev->dev, sizeof(*dln2));
+        if (!master)
+                return -ENOMEM;
+
+        platform_set_drvdata(pdev, master);
+
+        dln2 = spi_master_get_devdata(master);
+
+        dln2->buf = devm_kmalloc(&pdev->dev, DLN2_SPI_BUF_SIZE, GFP_KERNEL);
+        if (!dln2->buf) {
+                ret = -ENOMEM;
+                goto exit_free_master;
+        }
+
+        dln2->master = master;
+        dln2->pdev = pdev;
+        dln2->port = pdata->port;
+        /* cs/mode can never be 0xff, so the first transfer will set them */
+        dln2->cs = 0xff;
+        dln2->mode = 0xff;
+
+        /* disable SPI module before continuing with the setup */
+        ret = dln2_spi_enable(dln2, false);
+        if (ret < 0) {
+                dev_err(&pdev->dev, "Failed to disable SPI module\n");
+                goto exit_free_master;
+        }
+
+        ret = dln2_spi_get_cs_num(dln2, &master->num_chipselect);
+        if (ret < 0) {
+                dev_err(&pdev->dev, "Failed to get number of CS pins\n");
+                goto exit_free_master;
+        }
+
+        ret = dln2_spi_get_speed_range(dln2,
+                                       &master->min_speed_hz,
+                                       &master->max_speed_hz);
+        if (ret < 0) {
+                dev_err(&pdev->dev, "Failed to read bus min/max freqs\n");
+                goto exit_free_master;
+        }
+
+        ret = dln2_spi_get_supported_frame_sizes(dln2,
+                                                 &master->bits_per_word_mask);
+        if (ret < 0) {
+                dev_err(&pdev->dev, "Failed to read supported frame sizes\n");
+                goto exit_free_master;
+        }
+
+        ret = dln2_spi_cs_enable_all(dln2, true);
+        if (ret < 0) {
+                dev_err(&pdev->dev, "Failed to enable CS pins\n");
+                goto exit_free_master;
+        }
+
+        master->bus_num = -1;
+        master->mode_bits = SPI_CPOL | SPI_CPHA;
+        master->prepare_message = dln2_spi_prepare_message;
+        master->transfer_one = dln2_spi_transfer_one;
+        master->auto_runtime_pm = true;
+
+        /* enable SPI module, we're good to go */
+        ret = dln2_spi_enable(dln2, true);
+        if (ret < 0) {
+                dev_err(&pdev->dev, "Failed to enable SPI module\n");
+                goto exit_free_master;
+        }
+
+        pm_runtime_set_autosuspend_delay(&pdev->dev,
+                                         DLN2_RPM_AUTOSUSPEND_TIMEOUT);
+        pm_runtime_use_autosuspend(&pdev->dev);
+        pm_runtime_set_active(&pdev->dev);
+        pm_runtime_enable(&pdev->dev);
+
+        ret = devm_spi_register_master(&pdev->dev, master);
+        if (ret < 0) {
+                dev_err(&pdev->dev, "Failed to register master\n");
+                goto exit_register;
+        }
+
+        return ret;
+
+exit_register:
+        pm_runtime_disable(&pdev->dev);
+        pm_runtime_set_suspended(&pdev->dev);
+
+        if (dln2_spi_enable(dln2, false) < 0)
+                dev_err(&pdev->dev, "Failed to disable SPI module\n");
+exit_free_master:
+        spi_master_put(master);
+
+        return ret;
+}
+
+static int dln2_spi_remove(struct platform_device *pdev)
+{
+        struct spi_master *master = spi_master_get(platform_get_drvdata(pdev));
+        struct dln2_spi *dln2 = spi_master_get_devdata(master);
+
+        pm_runtime_disable(&pdev->dev);
+
+        if (dln2_spi_enable(dln2, false) < 0)
+                dev_err(&pdev->dev, "Failed to disable SPI module\n");
+
+        return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int dln2_spi_suspend(struct device *dev)
+{
+        int ret;
+        struct spi_master *master = dev_get_drvdata(dev);
+        struct dln2_spi *dln2 = spi_master_get_devdata(master);
+
+        ret = spi_master_suspend(master);
+        if (ret < 0)
+                return ret;
+
+        if (!pm_runtime_suspended(dev)) {
+                ret = dln2_spi_enable(dln2, false);
+                if (ret < 0)
+                        return ret;
+        }
+
+        /*
+         * USB power may be cut off during sleep. Resetting the following
+         * parameters will force the board to be set up before first transfer.
+         */
+        dln2->cs = 0xff;
+        dln2->speed = 0;
+        dln2->bpw = 0;
+        dln2->mode = 0xff;
+
+        return 0;
+}
+
+static int dln2_spi_resume(struct device *dev)
+{
+        int ret;
+        struct spi_master *master = dev_get_drvdata(dev);
+        struct dln2_spi *dln2 = spi_master_get_devdata(master);
+
+        if (!pm_runtime_suspended(dev)) {
+                ret = dln2_spi_cs_enable_all(dln2, true);
+                if (ret < 0)
+                        return ret;
+
+                ret = dln2_spi_enable(dln2, true);
+                if (ret < 0)
+                        return ret;
+        }
+
+        return spi_master_resume(master);
+}
+#endif /* CONFIG_PM_SLEEP */
+
+#ifdef CONFIG_PM_RUNTIME
+static int dln2_spi_runtime_suspend(struct device *dev)
+{
+        struct spi_master *master = dev_get_drvdata(dev);
+        struct dln2_spi *dln2 = spi_master_get_devdata(master);
+
+        return dln2_spi_enable(dln2, false);
+}
+
+static int dln2_spi_runtime_resume(struct device *dev)
+{
+        struct spi_master *master = dev_get_drvdata(dev);
+        struct dln2_spi *dln2 = spi_master_get_devdata(master);
+
+        return  dln2_spi_enable(dln2, true);
+}
+#endif /* CONFIG_PM_RUNTIME */
+
+static const struct dev_pm_ops dln2_spi_pm = {
+        SET_SYSTEM_SLEEP_PM_OPS(dln2_spi_suspend, dln2_spi_resume)
+        SET_RUNTIME_PM_OPS(dln2_spi_runtime_suspend,
+                           dln2_spi_runtime_resume, NULL)
+};
+
+static struct platform_driver spi_dln2_driver = {
+        .driver = {
+                .name   = "dln2-spi",
+                .pm     = &dln2_spi_pm,
+        },
+        .probe          = dln2_spi_probe,
+        .remove         = dln2_spi_remove,
+};
+module_platform_driver(spi_dln2_driver);
+
+MODULE_DESCRIPTION("Driver for the Diolan DLN2 SPI master interface");
+MODULE_AUTHOR("Laurentiu Palcu <laurentiu.palcu@intel.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:dln2-spi");