[PATCH v3 0/3] Virtio SPI Linux driver

[PATCH v3 0/3] Virtio SPI Linux driver

[Harald Mommer]

This is the 3rd non-RFC version of a virtio SPI Linux driver which is
intended to be compliant with the the upcoming virtio specification
version 1.4. The specification can be found in repository
https://github.com/oasis-tcs/virtio-spec.git branch virtio-1.4.

This driver is the successor of the 2nd non-RFC virtio driver.

Changes between 1st and 2nd virtio SPI driver RFC:

- Update from virtio SPI draft specification V4 to V10.

- Incorporate review comments gotten from the community.

A proposal for a performance enhancement having more than only one SPI
message in flight had to be kept out. The more complicated code would
have caused an unacceptable project risk now.

Changes between 2nd and 3rd virtio SPI driver RFC:

- Order header inclusion alphabetically

- Add Viresh Kumar's "signed-off" to the header files

- Rework virtio_spi_one_transfer()
  - Rework the delays according to Haixu Cui's advise. Delays are now
    handled in a new sub-function virtio_spi_set_delays()
  - Minor change: Re-formulate arguments of sg_init_one()

- Rework virtio_spi_probe()
  - Replace some goto in error paths by return
  - Add spi_unregister_controller() to an error path. Abstained from
    using devm_spi_register_controller() to keep order of
    de-initialization in virtio_spi_remove().
  - Add deletion of vqueue to all error paths taken after the virtqueues
    have been initialized

Changes between 3rd virtio SPI driver RFC and non-RFC driver V1

- Address kernel test robot comment which revealed an actual bug
- Rework some comments in the code addressing review comments
- Remove a TODO comment which has served it's purpose
- Allocate struct virtio_spi_req spi_req only once at startup
- Use callback transfer_one instead of transfer_one_message to simplify
  and shorten code. Due to this rework in the affected function(s) some
  additional changes:
  - Do init_completion() only once at startup, for re-initialization
    now reinit_completion() is used
  - Translate result codes VIRTIO_SPI_PARAM_ERR and VIRTIO_SPI_TRANS_ERR
    to appropriate Linux error codes -EINVAL and -EIO
  
Changes between 1st non-RFC virtio SPI driver and non-RFC driver V2

- Remove some comments stating the obvious
- Remove error trace when devm_spi_alloc_host() failed as this is habit
- Add some blank lines to improve readabilty
- Last TODO comment removed which was used to trigger some discussion.
  Discussion did not take place, most probably the code below is correct
  as it is

- Abstained from replacing "Cannot " by "Failed to " in error messages
  as the wording "Cannot " is frequently used even when "Failed to " has
  the majority. Announced this, heard nothing about this, so added the
  "Reviewed-by" from Viresh Kumar <viresh.kumar@linaro.org> as
  everything else was done.

Changes between non-RFC virtio SPI driver V2 and V3

- Child spi device tree nodes are supported now.

  If a child spi device tree node exists the setup of the user mode SPI
  device is done by spi_register_controller() and the driver itself does
  not call spi_new_device() any more to setup the chip selects.

  If there is no device tree child node the SPI device sets up the user
  mode SPI devices autonomously as it was before.

The virtio SPI driver was smoke tested on qemu using OpenSynergy's
proprietary virtio SPI device doing a SPI backend simulation on top of
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
branch next/stable at the time of testing (tagged v6.8). An almost
identical driver version was tested on hardware using kernel v6.5.7.

Removed "Reviewed-by" from Viresh Kumar <viresh.kumar@linaro.org> again
as the changes while small may be considered as substantial.

[PATCH v3 1/3] virtio: Add ID for virtio SPI.

[Harald Mommer]

From: Harald Mommer <harald.mommer@opensynergy.com>

Add #define ID VIRTIO_ID_SPI 45 for virtio SPI.

Signed-off-by: Harald Mommer <harald.mommer@opensynergy.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 include/uapi/linux/virtio_ids.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 7aa2eb766205..6c12db16faa3 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -68,6 +68,7 @@
 #define VIRTIO_ID_AUDIO_POLICY		39 /* virtio audio policy */
 #define VIRTIO_ID_BT			40 /* virtio bluetooth */
 #define VIRTIO_ID_GPIO			41 /* virtio gpio */
+#define VIRTIO_ID_SPI			45 /* virtio spi */
 
 /*
  * Virtio Transitional IDs
-- 
2.43.2

[PATCH v3 2/3] virtio-spi: Add virtio-spi.h.

[Harald Mommer]

From: Harald Mommer <harald.mommer@opensynergy.com>

Add virtio-spi.h header for virtio SPI.

Signed-off-by: Harald Mommer <harald.mommer@opensynergy.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 include/uapi/linux/virtio_spi.h | 185 ++++++++++++++++++++++++++++++++
 1 file changed, 185 insertions(+)
 create mode 100644 include/uapi/linux/virtio_spi.h

diff --git a/include/uapi/linux/virtio_spi.h b/include/uapi/linux/virtio_spi.h
new file mode 100644
index 000000000000..d6923f4080b4
--- /dev/null
+++ b/include/uapi/linux/virtio_spi.h
@@ -0,0 +1,185 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/*
+ * Copyright (C) 2023 OpenSynergy GmbH
+ */
+#ifndef _LINUX_VIRTIO_VIRTIO_SPI_H
+#define _LINUX_VIRTIO_VIRTIO_SPI_H
+
+#include <linux/types.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_ids.h>
+#include <linux/virtio_types.h>
+
+/* Sample data on trailing clock edge */
+#define VIRTIO_SPI_CPHA (1 << 0)
+/* Clock is high when IDLE */
+#define VIRTIO_SPI_CPOL (1 << 1)
+/* Chip Select is active high */
+#define VIRTIO_SPI_CS_HIGH (1 << 2)
+/* Transmit LSB first */
+#define VIRTIO_SPI_MODE_LSB_FIRST (1 << 3)
+/* Loopback mode */
+#define VIRTIO_SPI_MODE_LOOP (1 << 4)
+
+/*
+ * All config fields are read-only for the Virtio SPI driver
+ *
+ * @cs_max_number: maximum number of chipselect the host SPI controller
+ *   supports.
+ * @cs_change_supported: indicates if the host SPI controller supports to toggle
+ * chipselect after each transfer in one message:
+ *   0: unsupported, chipselect will be kept in active state throughout the
+ *      message transaction;
+ *   1: supported.
+ *   Note: Message here contains a sequence of SPI transfers.
+ * @tx_nbits_supported: indicates the supported number of bit for writing:
+ *   bit 0: DUAL (2-bit transfer), 1 for supported
+ *   bit 1: QUAD (4-bit transfer), 1 for supported
+ *   bit 2: OCTAL (8-bit transfer), 1 for supported
+ *   other bits are reserved as 0, 1-bit transfer is always supported.
+ * @rx_nbits_supported: indicates the supported number of bit for reading:
+ *   bit 0: DUAL (2-bit transfer), 1 for supported
+ *   bit 1: QUAD (4-bit transfer), 1 for supported
+ *   bit 2: OCTAL (8-bit transfer), 1 for supported
+ *   other bits are reserved as 0, 1-bit transfer is always supported.
+ * @bits_per_word_mask: mask indicating which values of bits_per_word are
+ *   supported. If not set, no limitation for bits_per_word.
+ * @mode_func_supported: indicates the following features are supported or not:
+ *   bit 0-1: CPHA feature
+ *     0b00: invalid, should support as least one CPHA setting
+ *     0b01: supports CPHA=0 only
+ *     0b10: supports CPHA=1 only
+ *     0b11: supports CPHA=0 and CPHA=1.
+ *   bit 2-3: CPOL feature
+ *     0b00: invalid, should support as least one CPOL setting
+ *     0b01: supports CPOL=0 only
+ *     0b10: supports CPOL=1 only
+ *     0b11: supports CPOL=0 and CPOL=1.
+ *   bit 4: chipselect active high feature, 0 for unsupported and 1 for
+ *     supported, chipselect active low should always be supported.
+ *   bit 5: LSB first feature, 0 for unsupported and 1 for supported,
+ *     MSB first should always be supported.
+ *   bit 6: loopback mode feature, 0 for unsupported and 1 for supported,
+ *     normal mode should always be supported.
+ * @max_freq_hz: the maximum clock rate supported in Hz unit, 0 means no
+ *   limitation for transfer speed.
+ * @max_word_delay_ns: the maximum word delay supported in ns unit,
+ *   0 means word delay feature is unsupported.
+ *   Note: Just as one message contains a sequence of transfers,
+ *         one transfer may contain a sequence of words.
+ * @max_cs_setup_ns: the maximum delay supported after chipselect is asserted,
+ *   in ns unit, 0 means delay is not supported to introduce after chipselect is
+ *   asserted.
+ * @max_cs_hold_ns: the maximum delay supported before chipselect is deasserted,
+ *   in ns unit, 0 means delay is not supported to introduce before chipselect
+ *   is deasserted.
+ * @max_cs_incative_ns: maximum delay supported after chipselect is deasserted,
+ *   in ns unit, 0 means delay is not supported to introduce after chipselect is
+ *   deasserted.
+ */
+struct virtio_spi_config {
+	/* # of /dev/spidev<bus_num>.CS with CS=0..chip_select_max_number -1 */
+	__u8 cs_max_number;
+	__u8 cs_change_supported;
+#define VIRTIO_SPI_RX_TX_SUPPORT_DUAL (1 << 0)
+#define VIRTIO_SPI_RX_TX_SUPPORT_QUAD (1 << 1)
+#define VIRTIO_SPI_RX_TX_SUPPORT_OCTAL (1 << 2)
+	__u8 tx_nbits_supported;
+	__u8 rx_nbits_supported;
+	__le32 bits_per_word_mask;
+#define VIRTIO_SPI_MF_SUPPORT_CPHA_0 (1 << 0)
+#define VIRTIO_SPI_MF_SUPPORT_CPHA_1 (1 << 1)
+#define VIRTIO_SPI_MF_SUPPORT_CPOL_0 (1 << 2)
+#define VIRTIO_SPI_MF_SUPPORT_CPOL_1 (1 << 3)
+#define VIRTIO_SPI_MF_SUPPORT_CS_HIGH (1 << 4)
+#define VIRTIO_SPI_MF_SUPPORT_LSB_FIRST (1 << 5)
+#define VIRTIO_SPI_MF_SUPPORT_LOOPBACK (1 << 6)
+	__le32 mode_func_supported;
+	__le32 max_freq_hz;
+	__le32 max_word_delay_ns;
+	__le32 max_cs_setup_ns;
+	__le32 max_cs_hold_ns;
+	__le32 max_cs_inactive_ns;
+};
+
+/*
+ * @chip_select_id: chipselect index the SPI transfer used.
+ *
+ * @bits_per_word: the number of bits in each SPI transfer word.
+ *
+ * @cs_change: whether to deselect device after finishing this transfer
+ *     before starting the next transfer, 0 means cs keep asserted and
+ *     1 means cs deasserted then asserted again.
+ *
+ * @tx_nbits: bus width for write transfer.
+ *     0,1: bus width is 1, also known as SINGLE
+ *     2  : bus width is 2, also known as DUAL
+ *     4  : bus width is 4, also known as QUAD
+ *     8  : bus width is 8, also known as OCTAL
+ *     other values are invalid.
+ *
+ * @rx_nbits: bus width for read transfer.
+ *     0,1: bus width is 1, also known as SINGLE
+ *     2  : bus width is 2, also known as DUAL
+ *     4  : bus width is 4, also known as QUAD
+ *     8  : bus width is 8, also known as OCTAL
+ *     other values are invalid.
+ *
+ * @reserved: for future use.
+ *
+ * @mode: SPI transfer mode.
+ *     bit 0: CPHA, determines the timing (i.e. phase) of the data
+ *         bits relative to the clock pulses.For CPHA=0, the
+ *         "out" side changes the data on the trailing edge of the
+ *         preceding clock cycle, while the "in" side captures the data
+ *         on (or shortly after) the leading edge of the clock cycle.
+ *         For CPHA=1, the "out" side changes the data on the leading
+ *         edge of the current clock cycle, while the "in" side
+ *         captures the data on (or shortly after) the trailing edge of
+ *         the clock cycle.
+ *     bit 1: CPOL, determines the polarity of the clock. CPOL=0 is a
+ *         clock which idles at 0, and each cycle consists of a pulse
+ *         of 1. CPOL=1 is a clock which idles at 1, and each cycle
+ *         consists of a pulse of 0.
+ *     bit 2: CS_HIGH, if 1, chip select active high, else active low.
+ *     bit 3: LSB_FIRST, determines per-word bits-on-wire, if 0, MSB
+ *         first, else LSB first.
+ *     bit 4: LOOP, loopback mode.
+ *
+ * @freq: the transfer speed in Hz.
+ *
+ * @word_delay_ns: delay to be inserted between consecutive words of a
+ *     transfer, in ns unit.
+ *
+ * @cs_setup_ns: delay to be introduced after CS is asserted, in ns
+ *     unit.
+ *
+ * @cs_delay_hold_ns: delay to be introduced before CS is deasserted
+ *     for each transfer, in ns unit.
+ *
+ * @cs_change_delay_inactive_ns: delay to be introduced after CS is
+ *     deasserted and before next asserted, in ns unit.
+ */
+struct spi_transfer_head {
+	__u8 chip_select_id;
+	__u8 bits_per_word;
+	__u8 cs_change;
+	__u8 tx_nbits;
+	__u8 rx_nbits;
+	__u8 reserved[3];
+	__le32 mode;
+	__le32 freq;
+	__le32 word_delay_ns;
+	__le32 cs_setup_ns;
+	__le32 cs_delay_hold_ns;
+	__le32 cs_change_delay_inactive_ns;
+};
+
+struct spi_transfer_result {
+#define VIRTIO_SPI_TRANS_OK 0
+#define VIRTIO_SPI_PARAM_ERR 1
+#define VIRTIO_SPI_TRANS_ERR 2
+	u8 result;
+};
+
+#endif /* #ifndef _LINUX_VIRTIO_VIRTIO_SPI_H */
-- 
2.43.2

[PATCH v3 3/3] virtio-spi: Add virtio SPI driver.

[Harald Mommer]

From: Harald Mommer <harald.mommer@opensynergy.com>

This is the virtio SPI Linux kernel driver.

Signed-off-by: Harald Mommer <Harald.Mommer@opensynergy.com>
---
 MAINTAINERS              |   6 +
 drivers/spi/Kconfig      |  11 +
 drivers/spi/Makefile     |   1 +
 drivers/spi/spi-virtio.c | 479 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 497 insertions(+)
 create mode 100644 drivers/spi/spi-virtio.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 1aabf1c15bb3..a370dd54896f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23384,6 +23384,12 @@ S:	Maintained
 F:	include/uapi/linux/virtio_snd.h
 F:	sound/virtio/*
 
+VIRTIO SPI DRIVER
+M:	Harald Mommer <harald.mommer@opensynergy.com>
+S:	Maintained
+F:	include/uapi/linux/virtio_spi.h
+F:	drivers/spi/spi-virtio.c
+
 VIRTUAL BOX GUEST DEVICE DRIVER
 M:	Hans de Goede <hdegoede@redhat.com>
 M:	Arnd Bergmann <arnd@arndb.de>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index ddae0fde798e..ff06e595679a 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -1125,6 +1125,17 @@ config SPI_UNIPHIER
 
 	  If your SoC supports SCSSI, say Y here.
 
+config SPI_VIRTIO
+	tristate "Virtio SPI Controller"
+	depends on SPI_MASTER && VIRTIO
+	help
+	  This enables the Virtio SPI driver.
+
+	  Virtio SPI is an SPI driver for virtual machines using Virtio.
+
+	  If your Linux is a virtual machine using Virtio, say Y here.
+	  If unsure, say N.
+
 config SPI_XCOMM
 	tristate "Analog Devices AD-FMCOMMS1-EBZ SPI-I2C-bridge driver"
 	depends on I2C
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 4ff8d725ba5e..ff2243e44e00 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -146,6 +146,7 @@ spi-thunderx-objs			:= spi-cavium.o spi-cavium-thunderx.o
 obj-$(CONFIG_SPI_THUNDERX)		+= spi-thunderx.o
 obj-$(CONFIG_SPI_TOPCLIFF_PCH)		+= spi-topcliff-pch.o
 obj-$(CONFIG_SPI_UNIPHIER)		+= spi-uniphier.o
+obj-$(CONFIG_SPI_VIRTIO)		+= spi-virtio.o
 obj-$(CONFIG_SPI_XCOMM)		+= spi-xcomm.o
 obj-$(CONFIG_SPI_XILINX)		+= spi-xilinx.o
 obj-$(CONFIG_SPI_XLP)			+= spi-xlp.o
diff --git a/drivers/spi/spi-virtio.c b/drivers/spi/spi-virtio.c
new file mode 100644
index 000000000000..06e8b3b62a94
--- /dev/null
+++ b/drivers/spi/spi-virtio.c
@@ -0,0 +1,479 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * SPI bus driver for the Virtio SPI controller
+ * Copyright (C) 2023 OpenSynergy GmbH
+ */
+
+#include <linux/completion.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/spi/spi.h>
+#include <linux/stddef.h>
+#include <linux/virtio.h>
+#include <linux/virtio_ring.h>
+#include <linux/virtio_spi.h>
+
+struct virtio_spi_req {
+	struct completion completion;
+	struct spi_transfer_head transfer_head	____cacheline_aligned;
+	const uint8_t *tx_buf			____cacheline_aligned;
+	uint8_t *rx_buf				____cacheline_aligned;
+	struct spi_transfer_result result	____cacheline_aligned;
+};
+
+struct virtio_spi_priv {
+	/* Virtio SPI message */
+	struct virtio_spi_req spi_req;
+	/* The virtio device we're associated with */
+	struct virtio_device *vdev;
+	/* Pointer to the virtqueue */
+	struct virtqueue *vq;
+	/* Copy of config space mode_func_supported */
+	u32 mode_func_supported;
+	/* Copy of config space max_freq_hz */
+	u32 max_freq_hz;
+};
+
+static struct spi_board_info board_info = {
+	.modalias = "spi-virtio",
+};
+
+static void virtio_spi_msg_done(struct virtqueue *vq)
+{
+	struct virtio_spi_req *req;
+	unsigned int len;
+
+	while ((req = virtqueue_get_buf(vq, &len)))
+		complete(&req->completion);
+}
+
+/*
+ *       .   .      .    .    .   .   .   .   .   .
+ * Delay + A +      + B  +    + C + D + E + F + A +
+ *       .   .      .    .    .   .   .   .   .   .
+ *    ___.   .      .    .    .   .   .___.___.   .
+ * CS#   |___.______.____.____.___.___|   .   |___._____________
+ *       .   .      .    .    .   .   .   .   .   .
+ *       .   .      .    .    .   .   .   .   .   .
+ * SCLK__.___.___NNN_____NNN__.___.___.___.___.___.___NNN_______
+ *
+ * NOTE: 1st transfer has two words, the delay between these two words are
+ * 'B' in the diagram.
+ *
+ * A => struct spi_device -> cs_setup
+ * B => max{struct spi_transfer -> word_delay, struct spi_device -> word_delay}
+ *   Note: spi_device and spi_transfer both have word_delay, Linux
+ *         choose the bigger one, refer to _spi_xfer_word_delay_update function
+ * C => struct spi_transfer -> delay
+ * D => struct spi_device -> cs_hold
+ * E => struct spi_device -> cs_inactive
+ * F => struct spi_transfer -> cs_change_delay
+ *
+ * So the corresponding relationship:
+ * A <===> cs_setup_ns (after CS asserted)
+ * B <===> word_delay_ns (no matter with CS)
+ * C+D <===> cs_delay_hold_ns (before CS deasserted)
+ * E+F <===> cs_change_delay_inactive_ns (after CS deasserted, these two
+ * values are also recommended in the Linux driver to be added up)
+ */
+static int virtio_spi_set_delays(struct spi_transfer_head *th,
+				 struct spi_device *spi,
+				 struct spi_transfer *xfer)
+{
+	int cs_setup;
+	int cs_word_delay_xfer;
+	int cs_word_delay_spi;
+	int delay;
+	int cs_hold;
+	int cs_inactive;
+	int cs_change_delay;
+
+	cs_setup = spi_delay_to_ns(&spi->cs_setup, xfer);
+	if (cs_setup < 0) {
+		dev_warn(&spi->dev, "Cannot convert cs_setup\n");
+		return cs_setup;
+	}
+	th->cs_setup_ns = cpu_to_le32((u32)cs_setup);
+
+	cs_word_delay_xfer = spi_delay_to_ns(&xfer->word_delay, xfer);
+	if (cs_word_delay_xfer < 0) {
+		dev_warn(&spi->dev, "Cannot convert cs_word_delay_xfer\n");
+		return cs_word_delay_xfer;
+	}
+	cs_word_delay_spi = spi_delay_to_ns(&spi->word_delay, xfer);
+	if (cs_word_delay_spi < 0) {
+		dev_warn(&spi->dev, "Cannot convert cs_word_delay_spi\n");
+		return cs_word_delay_spi;
+	}
+	if (cs_word_delay_spi > cs_word_delay_xfer)
+		th->word_delay_ns = cpu_to_le32((u32)cs_word_delay_spi);
+	else
+		th->word_delay_ns = cpu_to_le32((u32)cs_word_delay_xfer);
+
+	delay = spi_delay_to_ns(&xfer->delay, xfer);
+	if (delay < 0) {
+		dev_warn(&spi->dev, "Cannot convert delay\n");
+		return delay;
+	}
+	cs_hold = spi_delay_to_ns(&spi->cs_hold, xfer);
+	if (cs_hold < 0) {
+		dev_warn(&spi->dev, "Cannot convert cs_hold\n");
+		return cs_hold;
+	}
+	th->cs_delay_hold_ns = cpu_to_le32((u32)delay + (u32)cs_hold);
+
+	cs_inactive = spi_delay_to_ns(&spi->cs_inactive, xfer);
+	if (cs_inactive < 0) {
+		dev_warn(&spi->dev, "Cannot convert cs_inactive\n");
+		return cs_inactive;
+	}
+	cs_change_delay = spi_delay_to_ns(&xfer->cs_change_delay, xfer);
+	if (cs_change_delay < 0) {
+		dev_warn(&spi->dev, "Cannot convert cs_change_delay\n");
+		return cs_change_delay;
+	}
+	th->cs_change_delay_inactive_ns =
+		cpu_to_le32((u32)cs_inactive + (u32)cs_change_delay);
+
+	return 0;
+}
+
+static int virtio_spi_transfer_one(struct spi_controller *ctrl,
+				   struct spi_device *spi,
+				   struct spi_transfer *xfer)
+{
+	struct virtio_spi_priv *priv = spi_controller_get_devdata(ctrl);
+	struct virtio_spi_req *spi_req = &priv->spi_req;
+	struct spi_transfer_head *th;
+	struct scatterlist sg_out_head, sg_out_payload;
+	struct scatterlist sg_in_result, sg_in_payload;
+	struct scatterlist *sgs[4];
+	unsigned int outcnt = 0u;
+	unsigned int incnt = 0u;
+	int ret;
+
+	th = &spi_req->transfer_head;
+
+	/* Fill struct spi_transfer_head */
+	th->chip_select_id = spi_get_chipselect(spi, 0);
+	th->bits_per_word = spi->bits_per_word;
+	th->cs_change = xfer->cs_change;
+	th->tx_nbits = xfer->tx_nbits;
+	th->rx_nbits = xfer->rx_nbits;
+	th->reserved[0] = 0;
+	th->reserved[1] = 0;
+	th->reserved[2] = 0;
+
+	BUILD_BUG_ON(VIRTIO_SPI_CPHA != SPI_CPHA);
+	BUILD_BUG_ON(VIRTIO_SPI_CPOL != SPI_CPOL);
+	BUILD_BUG_ON(VIRTIO_SPI_CS_HIGH != SPI_CS_HIGH);
+	BUILD_BUG_ON(VIRTIO_SPI_MODE_LSB_FIRST != SPI_LSB_FIRST);
+
+	th->mode = cpu_to_le32(spi->mode & (SPI_LSB_FIRST | SPI_CS_HIGH |
+					    SPI_CPOL | SPI_CPHA));
+	if ((spi->mode & SPI_LOOP) != 0)
+		th->mode |= cpu_to_le32(VIRTIO_SPI_MODE_LOOP);
+
+	th->freq = cpu_to_le32(xfer->speed_hz);
+
+	ret = virtio_spi_set_delays(th, spi, xfer);
+	if (ret)
+		goto msg_done;
+
+	/* Set buffers */
+	spi_req->tx_buf = xfer->tx_buf;
+	spi_req->rx_buf = xfer->rx_buf;
+
+	/* Prepare sending of virtio message */
+	reinit_completion(&spi_req->completion);
+
+	sg_init_one(&sg_out_head, th, sizeof(*th));
+	sgs[outcnt] = &sg_out_head;
+	outcnt++;
+
+	if (spi_req->tx_buf) {
+		sg_init_one(&sg_out_payload, spi_req->tx_buf, xfer->len);
+		sgs[outcnt] = &sg_out_payload;
+		outcnt++;
+	}
+
+	if (spi_req->rx_buf) {
+		sg_init_one(&sg_in_payload, spi_req->rx_buf, xfer->len);
+		sgs[outcnt] = &sg_in_payload;
+		incnt++;
+	}
+
+	sg_init_one(&sg_in_result, &spi_req->result,
+		    sizeof(struct spi_transfer_result));
+	sgs[outcnt + incnt] = &sg_in_result;
+	incnt++;
+
+	ret = virtqueue_add_sgs(priv->vq, sgs, outcnt, incnt, spi_req,
+				GFP_KERNEL);
+	if (ret)
+		goto msg_done;
+
+	/* Simple implementation: There can be only one transfer in flight */
+	virtqueue_kick(priv->vq);
+
+	wait_for_completion(&priv->spi_req.completion);
+
+	/* Read result from message and translate return code */
+	switch (priv->spi_req.result.result) {
+	case VIRTIO_SPI_TRANS_OK:
+		/* ret is 0 */
+		break;
+	case VIRTIO_SPI_PARAM_ERR:
+		ret = -EINVAL;
+		break;
+	case VIRTIO_SPI_TRANS_ERR:
+		ret = -EIO;
+		break;
+	default: /* Protocol violation */
+		ret = -EIO;
+		break;
+	}
+
+msg_done:
+	if (ret)
+		ctrl->cur_msg->status = ret;
+
+	return ret;
+}
+
+static void virtio_spi_read_config(struct virtio_device *vdev)
+{
+	struct spi_controller *ctrl = dev_get_drvdata(&vdev->dev);
+	struct virtio_spi_priv *priv = vdev->priv;
+	u8 cs_max_number;
+	u8 tx_nbits_supported;
+	u8 rx_nbits_supported;
+
+	cs_max_number = virtio_cread8(vdev, offsetof(struct virtio_spi_config,
+						     cs_max_number));
+	ctrl->num_chipselect = cs_max_number;
+
+	/* Set the mode bits which are understood by this driver */
+	priv->mode_func_supported =
+		virtio_cread32(vdev, offsetof(struct virtio_spi_config,
+					      mode_func_supported));
+	ctrl->mode_bits = priv->mode_func_supported &
+			  (VIRTIO_SPI_CS_HIGH | VIRTIO_SPI_MODE_LSB_FIRST);
+	if ((priv->mode_func_supported & VIRTIO_SPI_MF_SUPPORT_CPHA_1) != 0)
+		ctrl->mode_bits |= VIRTIO_SPI_CPHA;
+	if ((priv->mode_func_supported & VIRTIO_SPI_MF_SUPPORT_CPOL_1) != 0)
+		ctrl->mode_bits |= VIRTIO_SPI_CPOL;
+	if ((priv->mode_func_supported & VIRTIO_SPI_MF_SUPPORT_LSB_FIRST) != 0)
+		ctrl->mode_bits |= SPI_LSB_FIRST;
+	if ((priv->mode_func_supported & VIRTIO_SPI_MF_SUPPORT_LOOPBACK) != 0)
+		ctrl->mode_bits |= SPI_LOOP;
+	tx_nbits_supported =
+		virtio_cread8(vdev, offsetof(struct virtio_spi_config,
+					     tx_nbits_supported));
+	if ((tx_nbits_supported & VIRTIO_SPI_RX_TX_SUPPORT_DUAL) != 0)
+		ctrl->mode_bits |= SPI_TX_DUAL;
+	if ((tx_nbits_supported & VIRTIO_SPI_RX_TX_SUPPORT_QUAD) != 0)
+		ctrl->mode_bits |= SPI_TX_QUAD;
+	if ((tx_nbits_supported & VIRTIO_SPI_RX_TX_SUPPORT_OCTAL) != 0)
+		ctrl->mode_bits |= SPI_TX_OCTAL;
+	rx_nbits_supported =
+		virtio_cread8(vdev, offsetof(struct virtio_spi_config,
+					     rx_nbits_supported));
+	if ((rx_nbits_supported & VIRTIO_SPI_RX_TX_SUPPORT_DUAL) != 0)
+		ctrl->mode_bits |= SPI_RX_DUAL;
+	if ((rx_nbits_supported & VIRTIO_SPI_RX_TX_SUPPORT_QUAD) != 0)
+		ctrl->mode_bits |= SPI_RX_QUAD;
+	if ((rx_nbits_supported & VIRTIO_SPI_RX_TX_SUPPORT_OCTAL) != 0)
+		ctrl->mode_bits |= SPI_RX_OCTAL;
+
+	ctrl->bits_per_word_mask =
+		virtio_cread32(vdev, offsetof(struct virtio_spi_config,
+					      bits_per_word_mask));
+
+	priv->max_freq_hz =
+		virtio_cread32(vdev, offsetof(struct virtio_spi_config,
+					      max_freq_hz));
+}
+
+static int virtio_spi_find_vqs(struct virtio_spi_priv *priv)
+{
+	struct virtqueue *vq;
+
+	vq = virtio_find_single_vq(priv->vdev, virtio_spi_msg_done, "spi-rq");
+	if (IS_ERR(vq))
+		return (int)PTR_ERR(vq);
+	priv->vq = vq;
+	return 0;
+}
+
+/* Function must not be called before virtio_spi_find_vqs() has been run */
+static void virtio_spi_del_vq(struct virtio_device *vdev)
+{
+	virtio_reset_device(vdev);
+	vdev->config->del_vqs(vdev);
+}
+
+static int virtio_spi_validate(struct virtio_device *vdev)
+{
+	/*
+	 * SPI needs always access to the config space.
+	 * Check that the driver can access the config space
+	 */
+	if (!vdev->config->get) {
+		dev_err(&vdev->dev, "%s failure: config access disabled\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
+		dev_err(&vdev->dev,
+			"device does not comply with spec version 1.x\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int virtio_spi_probe(struct virtio_device *vdev)
+{
+	struct device_node *np = vdev->dev.parent->of_node;
+	struct virtio_spi_priv *priv;
+	struct spi_controller *ctrl;
+	int err;
+	u32 bus_num;
+	u16 csi;
+
+	ctrl = devm_spi_alloc_host(&vdev->dev, sizeof(*priv));
+	if (!ctrl)
+		return -ENOMEM;
+
+	priv = spi_controller_get_devdata(ctrl);
+	priv->vdev = vdev;
+	vdev->priv = priv;
+	ctrl->dev.of_node = vdev->dev.of_node;
+	dev_set_drvdata(&vdev->dev, ctrl);
+
+	init_completion(&priv->spi_req.completion);
+
+	err = of_property_read_u32(np, "spi,bus-num", &bus_num);
+	if (!err && bus_num <= S16_MAX)
+		ctrl->bus_num = (s16)bus_num;
+
+	virtio_spi_read_config(vdev);
+
+	ctrl->transfer_one = virtio_spi_transfer_one;
+
+	err = virtio_spi_find_vqs(priv);
+	if (err) {
+		dev_err(&vdev->dev, "Cannot setup virtqueues\n");
+		return err;
+	}
+
+	board_info.max_speed_hz = priv->max_freq_hz;
+	board_info.bus_num = (u16)ctrl->bus_num;
+
+	if (!(priv->mode_func_supported & VIRTIO_SPI_CS_HIGH))
+		board_info.mode = SPI_MODE_0;
+	else
+		board_info.mode = SPI_MODE_0 | SPI_CS_HIGH;
+
+	err = spi_register_controller(ctrl);
+	if (err) {
+		dev_err(&vdev->dev, "Cannot register controller\n");
+		goto err_return;
+	}
+
+	if (vdev->dev.of_node) {
+		dev_dbg(&vdev->dev, "Final setup triggered by DT child node\n");
+		return 0;
+	}
+
+	/* Add chip selects to controller */
+	for (csi = 0; csi < ctrl->num_chipselect; csi++) {
+		dev_dbg(&vdev->dev, "Setting up CS=%u\n", csi);
+		board_info.chip_select = csi;
+
+		if (!spi_new_device(ctrl, &board_info)) {
+			dev_err(&vdev->dev, "Cannot setup device %u\n", csi);
+			spi_unregister_controller(ctrl);
+			err = -ENODEV;
+			goto err_return;
+		}
+	}
+
+	return 0;
+
+err_return:
+	vdev->config->del_vqs(vdev);
+	return err;
+}
+
+static void virtio_spi_remove(struct virtio_device *vdev)
+{
+	struct spi_controller *ctrl = dev_get_drvdata(&vdev->dev);
+
+	/* Order: 1.) unregister controller, 2.) remove virtqueue */
+	spi_unregister_controller(ctrl);
+	virtio_spi_del_vq(vdev);
+}
+
+static int virtio_spi_freeze(struct virtio_device *vdev)
+{
+	struct device *dev = &vdev->dev;
+	struct spi_controller *ctrl = dev_get_drvdata(dev);
+	int ret;
+
+	ret = spi_controller_suspend(ctrl);
+	if (ret) {
+		dev_warn(dev, "cannot suspend controller (%d)\n", ret);
+		return ret;
+	}
+
+	virtio_spi_del_vq(vdev);
+	return 0;
+}
+
+static int virtio_spi_restore(struct virtio_device *vdev)
+{
+	struct device *dev = &vdev->dev;
+	struct spi_controller *ctrl = dev_get_drvdata(dev);
+	int ret;
+
+	ret = virtio_spi_find_vqs(vdev->priv);
+	if (ret) {
+		dev_err(dev, "problem starting vqueue (%d)\n", ret);
+		return ret;
+	}
+
+	ret = spi_controller_resume(ctrl);
+	if (ret)
+		dev_err(dev, "problem resuming controller (%d)\n", ret);
+
+	return ret;
+}
+
+static struct virtio_device_id virtio_spi_id_table[] = {
+	{ VIRTIO_ID_SPI, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static struct virtio_driver virtio_spi_driver = {
+	.driver.name = KBUILD_MODNAME,
+	.driver.owner = THIS_MODULE,
+	.id_table = virtio_spi_id_table,
+	.validate = virtio_spi_validate,
+	.probe = virtio_spi_probe,
+	.remove = virtio_spi_remove,
+	.freeze = pm_sleep_ptr(virtio_spi_freeze),
+	.restore = pm_sleep_ptr(virtio_spi_restore),
+};
+
+module_virtio_driver(virtio_spi_driver);
+MODULE_DEVICE_TABLE(virtio, virtio_spi_id_table);
+
+MODULE_AUTHOR("OpenSynergy GmbH");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Virtio SPI bus driver");
-- 
2.43.2