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

[Qiang Zhang]

Hi, Harald

On Tue, Mar 26, 2024 at 12:28:12PM +0100, Harald Mommer wrote:
> From: Harald Mommer <harald.mommer@xxxxxxxxxxxxxxx>
> 
> This is the virtio SPI Linux kernel driver.
> 
> Signed-off-by: Harald Mommer <Harald.Mommer@xxxxxxxxxxxxxxx>
[...]
> +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;

To support ACPI, ACPI node of the controller needs to be set:

	/*
	 * Setup ACPI node for controlled devices which will be probed through
	 * ACPI.
	 */
	ACPI_COMPANION_SET(&vdev->dev, ACPI_COMPANION(vdev->dev.parent));

> +	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;

This is not the right way to fix bus number. You can use OF alias.
Also, to work with ACPI, we should use common API like
device_property_read_u32.

> +
> +	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;
> +	}
How about ACPI path?
> +
> +	/* 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;
> +		}
> +	}
Just enumerate SPI devices via DT/ACPI. And a fixed SPI modalias "spi-virtio"
is no better than match method from DT/ACPI.

Thanks,
Qiang