[v2,3/3] virtio-spi: Add virtio SPI driver.

Commit Message

Harald Mommer March 4, 2024, 3:43 p.m. UTC

From: Harald Mommer <[e-mail]>

This is the virtio SPI Linux kernel driver.

Signed-off-by: Harald Mommer <[e-mail]>
Reviewed-by: Viresh Kumar <[e-mail]>
---
 MAINTAINERS              |   6 +
 drivers/spi/Kconfig      |  11 +
 drivers/spi/Makefile     |   1 +
 drivers/spi/spi-virtio.c | 474 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 492 insertions(+)
 create mode 100644 drivers/spi/spi-virtio.c

Comments

Haixu Cui March 14, 2024, 9:17 a.m. UTC | #1

Hello,

     Please refer to my comments in virtio_spi_probe function.

On 3/4/2024 11:43 PM, Harald Mommer wrote:
> From: Harald Mommer <[e-mail]>
> 
> This is the virtio SPI Linux kernel driver.
> 
> Signed-off-by: Harald Mommer <[e-mail]>
> Reviewed-by: Viresh Kumar <[e-mail]>
> ---
>   MAINTAINERS              |   6 +
>   drivers/spi/Kconfig      |  11 +
>   drivers/spi/Makefile     |   1 +
>   drivers/spi/spi-virtio.c | 474 +++++++++++++++++++++++++++++++++++++++
>   4 files changed, 492 insertions(+)
>   create mode 100644 drivers/spi/spi-virtio.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 4f298c4187fb..42bc6ae594ce 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 <[e-mail]>
> +S:	Maintained
> +F:	include/uapi/linux/virtio_spi.h
> +F:	drivers/spi/spi-virtio.c
> +
>   VIRTUAL BOX GUEST DEVICE DRIVER
>   M:	Hans de Goede <[e-mail]>
>   M:	Arnd Bergmann <[e-mail]>
> 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..4f22b03fb678
> --- /dev/null
> +++ b/drivers/spi/spi-virtio.c
> @@ -0,0 +1,474 @@
> +// 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;
> +	dev_set_drvdata(&vdev->dev, ctrl);

     Here should set ctrl->dev.of_node, to scan the child nodes.

> +
> +	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;
> +	}
> +
> +	err = spi_register_controller(ctrl);
> +	if (err) {
> +		dev_err(&vdev->dev, "Cannot register controller\n");
> +		goto err_return;
> +	}
> +
> +	board_info.max_speed_hz = priv->max_freq_hz;
> +	/* spi_new_device() currently does not use bus_num but better set it */
> +	board_info.bus_num = (u16)ctrl->bus_num;
> +

     Please refer to my comments above your previous patch, here 
createing spi devices staticly, will introduce conflicts if there is 
virtio spi device node in device-tree.

> +	/* 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 (!(priv->mode_func_supported & VIRTIO_SPI_CS_HIGH))
> +			board_info.mode = SPI_MODE_0;
> +		else
> +			board_info.mode = SPI_MODE_0 | SPI_CS_HIGH;
> +
> +		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");

Mark Brown March 14, 2024, 1:35 p.m. UTC | #2

On Thu, Mar 14, 2024 at 05:17:50PM +0800, Haixu Cui wrote:
> 
> Hello,
> 
>     Please refer to my comments in virtio_spi_probe function.
> 
> On 3/4/2024 11:43 PM, Harald Mommer wrote:
> > From: Harald Mommer <[e-mail]>
> > 
> > This is the virtio SPI Linux kernel driver.

Please delete unneeded context from mails when replying.  Doing this
makes it much easier to find your reply in the message, helping ensure
it won't be missed by people scrolling through the irrelevant quoted
material.

Haixu Cui March 18, 2024, 9:39 a.m. UTC | #3

Hello,

     As Mark recommended, I reserve the virtio_spi_probe function only 
and list my comments.

On 3/4/2024 11:43 PM, Harald Mommer wrote:
> +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;
> +	dev_set_drvdata(&vdev->dev, ctrl);

     ctrl->dev.of_node is not set, so the child node cannot be parsed. I 
would say, it's necessary to support the virtio spi device node in the 
format:

     virtio-spi@4b013000 {
         compatible = "virtio,mmio";
         reg = <0x4b013000 0x1000>;
         interrupts = <0 497 4>;

         spi {
             compatible = "virtio,device2d";
             #address-cells = <1>;
             #size-cells = <0>;

             spidev {
                 compatible = "xxx";
                 reg = <0>;
                 spi-max-frequency = <100000>;
             };
         };
     };
> +
> +	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;
> +	}
> +
> +	err = spi_register_controller(ctrl);
> +	if (err) {
> +		dev_err(&vdev->dev, "Cannot register controller\n");
> +		goto err_return;
> +	}
> +
> +	board_info.max_speed_hz = priv->max_freq_hz;
> +	/* spi_new_device() currently does not use bus_num but better set it */
> +	board_info.bus_num = (u16)ctrl->bus_num;
> +
> +	/* Add chip selects to controller */

         Creating the spi devices here statically, will introduce 
conflicts if the same spi devices also in the device-tree.

> +	for (csi = 0; csi < ctrl->num_chipselect; csi++) {
> +		dev_dbg(&vdev->dev, "Setting up CS=%u\n", csi);
> +		board_info.chip_select = csi;
> +
> +		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;
> +
> +		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;
> +}
> +

Harald Mommer March 19, 2024, 3:05 p.m. UTC | #4

Hello,

virtio-dev still down...

I have to admit when it comes to device trees it's most of the time a 
fight. You will see below, fighting.

On 18.03.24 10:39, Haixu Cui wrote:
> Hello,
>
>     As Mark recommended, I reserve the virtio_spi_probe function only 
> and list my comments.
>
> On 3/4/2024 11:43 PM, Harald Mommer wrote:
>> +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;
>> +    dev_set_drvdata(&vdev->dev, ctrl);
>
>     ctrl->dev.of_node is not set, so the child node cannot be parsed. 
> I would say, it's necessary to support the virtio spi device node in 
> the format:


What you most probably want to have here is

   ctrl->dev.of_node = np;

for reasons I don't understand completely yet but have some idea. I may 
play around to get it.


>
>     virtio-spi@4b013000 {
>         compatible = "virtio,mmio";
>         reg = <0x4b013000 0x1000>;
>         interrupts = <0 497 4>;
>
>         spi {
>             compatible = "virtio,device2d";
>             #address-cells = <1>;
>             #size-cells = <0>;
>
>             spidev {
>                 compatible = "xxx";
>                 reg = <0>;
>                 spi-max-frequency = <100000>;
>             };
>         };
>     };


Looks in my setup like this:

virtio_mmio@4b013000 {
   compatible = "virtio,mmio";
   reg = <0x0 0x4b013000 0x0 0x1000>;
   /* GIC_SPI = 0, IRQ_TYPE_LEVEL_HIGH = 4 */
   interrupts = <0 497 4>;
   spi,bus-num = <1234>; /* <<<=== This here has been added */
};

The "spi,bus-num" is missing in your setup so you use the default of 0.

For what is "reg = <0>;" good? Or is it a dummy and only has to be present?

I don't understand spi-max-frequency in the device tree entry as we get 
this value from the config space.


>> +
>> +    init_completion(&priv->spi_req.completion);
>> +
>> +    err = of_property_read_u32(np, "spi,bus-num", &bus_num);


np already set so this assignment should play no role here when reading 
the entry.


>> +    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;
>> +    }
>> +
>> +    err = spi_register_controller(ctrl);
>> +    if (err) {
>> +        dev_err(&vdev->dev, "Cannot register controller\n");
>> +        goto err_return;
>> +    }
>> +
>> +    board_info.max_speed_hz = priv->max_freq_hz;
>> +    /* spi_new_device() currently does not use bus_num but better 
>> set it */
>> +    board_info.bus_num = (u16)ctrl->bus_num;
>> +
>> +    /* Add chip selects to controller */
>
>         Creating the spi devices here statically, will introduce 
> conflicts if the same spi devices also in the device-tree.


Of course I need to create the SPI devices here statically. The 
"spi,bus-num = <1234>;" in the device tree has to be defined in a way 
that there are no conflicts. I do not understand this.


>
>> +    for (csi = 0; csi < ctrl->num_chipselect; csi++) {
>> +        dev_dbg(&vdev->dev, "Setting up CS=%u\n", csi);
>> +        board_info.chip_select = csi;
>> +
>> +        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;
>> +
>> +        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;
>> +}
>> +
>

What I needed to support for our needs was a user space SPI interface. 
You probably have a different setup and additional more complex device 
tree configuration needs I do not understand (yet). I'm somewhat lost in 
the moment.

Mark Brown March 19, 2024, 5:11 p.m. UTC | #5

On Tue, Mar 19, 2024 at 04:05:55PM +0100, Harald Mommer wrote:
> On 18.03.24 10:39, Haixu Cui wrote:

> Looks in my setup like this:
> 
> virtio_mmio@4b013000 {
>   compatible = "virtio,mmio";
>   reg = <0x0 0x4b013000 0x0 0x1000>;
>   /* GIC_SPI = 0, IRQ_TYPE_LEVEL_HIGH = 4 */
>   interrupts = <0 497 4>;
>   spi,bus-num = <1234>; /* <<<=== This here has been added */
> };
> 
> The "spi,bus-num" is missing in your setup so you use the default of 0.

The default should be dynamic assignment, why would you need a fixed bus
number?

Viresh Kumar March 20, 2024, 3:12 a.m. UTC | #6

Hi Harald,

On 19-03-24, 16:05, Harald Mommer wrote:
> On 18.03.24 10:39, Haixu Cui wrote:
> > On 3/4/2024 11:43 PM, Harald Mommer wrote:
> > > +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;
> > > +    dev_set_drvdata(&vdev->dev, ctrl);
> > 
> >     ctrl->dev.of_node is not set, so the child node cannot be parsed. I
> > would say, it's necessary to support the virtio spi device node in the
> > format:
> 
> 
> What you most probably want to have here is
> 
>   ctrl->dev.of_node = np;

Looking at how i2c-virtio does it, it should be tied to the device itself
instead of its parent:

ctrl->dev.of_node = vdev->dev.of_node;

> >     virtio-spi@4b013000 {
> >         compatible = "virtio,mmio";
> >         reg = <0x4b013000 0x1000>;
> >         interrupts = <0 497 4>;
> > 
> >         spi {
> >             compatible = "virtio,device2d";
> >             #address-cells = <1>;
> >             #size-cells = <0>;
> > 
> >             spidev {
> >                 compatible = "xxx";
> >                 reg = <0>;
> >                 spi-max-frequency = <100000>;
> >             };
> >         };
> >     };

Right, some work was done in the past to standardize these compatibles:

$ git log -p --stat --reverse 0d8c9e7d4b40..694a1116b405

Haixu Cui March 26, 2024, 9:26 a.m. UTC | #7

Hi all,

On 3/20/2024 11:12 AM, Viresh Kumar wrote:
> Hi Harald,
> 
> On 19-03-24, 16:05, Harald Mommer wrote:
>> On 18.03.24 10:39, Haixu Cui wrote:
>>> On 3/4/2024 11:43 PM, Harald Mommer wrote:
>>>> +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;
>>>> +    dev_set_drvdata(&vdev->dev, ctrl);
>>>
>>>      ctrl->dev.of_node is not set, so the child node cannot be parsed. I
>>> would say, it's necessary to support the virtio spi device node in the
>>> format:
>>
>>
>> What you most probably want to have here is
>>
>>    ctrl->dev.of_node = np;
> 
> Looking at how i2c-virtio does it, it should be tied to the device itself
> instead of its parent:

Yes, it is
         ctrl->dev.of_node = vdev->dev.of_node;

> 
> ctrl->dev.of_node = vdev->dev.of_node;
> 
>>>      virtio-spi@4b013000 {
>>>          compatible = "virtio,mmio";
>>>          reg = <0x4b013000 0x1000>;
>>>          interrupts = <0 497 4>;
>>>
>>>          spi {
>>>              compatible = "virtio,device2d";
>>>              #address-cells = <1>;
>>>              #size-cells = <0>;
>>>
>>>              spidev {
>>>                  compatible = "xxx";
>>>                  reg = <0>;
>>>                  spi-max-frequency = <100000>;
>>>              };
>>>          };
>>>      };
> 
> Right, some work was done in the past to standardize these compatibles:
> 
> $ git log -p --stat --reverse 0d8c9e7d4b40..694a1116b405
> 
     Here I would like the inner layer "spidev", to match then probe the 
spidev driver, the "reg" is the chip select index. "spi-max-frequency" 
is not necessary, while It doesn't matter.

     You can also customize the inner layer to match your own driver.

     In my test, I set the cs max number as 1, and in device tree node 
inner layer, reg as 0. So certainly spidev driver probed and spidev0.0 
is added successfully.

     But then the driver proceed to the following code, chip select 
index 0 device is created again, the driver fail with log: "chipselect 0 
already in use".

         for (csi = 0; csi < ctrl->num_chipselect; csi++) {
             dev_dbg(&vdev->dev, "Setting up CS=%u\n", csi);
             board_info.chip_select = csi;

             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;

             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;
             }
         }


     I hope I made myself clear. Thank you, Harald and Kumar. Best regards.

Harald Mommer March 26, 2024, 11:19 a.m. UTC | #8

Hello,

On 26.03.24 10:26, Haixu Cui wrote:
>
>> Looking at how i2c-virtio does it, it should be tied to the device 
>> itself
>> instead of its parent:
>
> Yes, it is
>         ctrl->dev.of_node = vdev->dev.of_node;


got it when looking into Viresh's code changes.


>>
>> Right, some work was done in the past to standardize these compatibles:
>>
>> $ git log -p --stat --reverse 0d8c9e7d4b40..694a1116b405
>>
>     Here I would like the inner layer "spidev", to match then probe 
> the spidev driver, the "reg" is the chip select index. 
> "spi-max-frequency" is not necessary, while It doesn't matter.
>
>     You can also customize the inner layer to match your own driver.
>
>     In my test, I set the cs max number as 1, and in device tree node 
> inner layer, reg as 0. So certainly spidev driver probed and spidev0.0 
> is added successfully.
>
>     But then the driver proceed to the following code, chip select 
> index 0 device is created again, the driver fail with log: "chipselect 
> 0 already in use".


The following lines

     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;

are moved before the sequence

     err = spi_register_controller(ctrl);
     if (err) {
         dev_err(&vdev->dev, "Cannot register controller\n");
         goto err_return;
     }

     if (vdev->dev.of_node) { // <=== This block is new
         dev_dbg(&vdev->dev, "Final setup triggered by DT child node\n");
         return 0;
     }

>
>         for (csi = 0; csi < ctrl->num_chipselect; csi++) {
>             dev_dbg(&vdev->dev, "Setting up CS=%u\n", csi);
>             board_info.chip_select = csi;
>
>             if (!(priv->mode_func_supported & VIRTIO_SPI_CS_HIGH)) // 
> <=== This if else is moved up. It is csi invariant anyway.
>                 board_info.mode = SPI_MODE_0;
>             else
>                 board_info.mode = SPI_MODE_0 | SPI_CS_HIGH;
>
>             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;
>             }
>         }
>
>

This means when there is no device tree entry everything behaves as 
before (for loop executed) and if there is a device tree entry the chip 
select will be setup already by spi_register_controller() and the for 
loop need not and will not be executed not annoying anyone with 
"chipselect 0 already in use".

I was undecided whether to keep Viresh Kumar's "reviewed by" in the 
commit message because I'm unsure whether this is to be considered as a 
substantial change. Changes are small but program logic is changed (vs. 
change of comment, removal of trace, change of trace wording) so I think 
it may be considered as a substantial change and therefore I'll remove 
the "reviewed-by" now.

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index 4f298c4187fb..42bc6ae594ce 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 <[e-mail]>
+S:	Maintained
+F:	include/uapi/linux/virtio_spi.h
+F:	drivers/spi/spi-virtio.c
+
 VIRTUAL BOX GUEST DEVICE DRIVER
 M:	Hans de Goede <[e-mail]>
 M:	Arnd Bergmann <[e-mail]>
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..4f22b03fb678
--- /dev/null
+++ b/drivers/spi/spi-virtio.c
@@ -0,0 +1,474 @@ 
+// 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;
+	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;
+	}
+
+	err = spi_register_controller(ctrl);
+	if (err) {
+		dev_err(&vdev->dev, "Cannot register controller\n");
+		goto err_return;
+	}
+
+	board_info.max_speed_hz = priv->max_freq_hz;
+	/* spi_new_device() currently does not use bus_num but better set it */
+	board_info.bus_num = (u16)ctrl->bus_num;
+
+	/* 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 (!(priv->mode_func_supported & VIRTIO_SPI_CS_HIGH))
+			board_info.mode = SPI_MODE_0;
+		else
+			board_info.mode = SPI_MODE_0 | SPI_CS_HIGH;
+
+		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");