linux-kernel - Re: [PATCH v2 3/3] virtio-spi: Add virtio SPI driver.

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Date: Mon, 18 Mar 2024 17:39:45 +0800
From: Haixu Cui <quic_haixcui@...cinc.com>
To: Harald Mommer <Harald.Mommer@...nsynergy.com>,
        Mark Brown
	<broonie@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>, <linux-spi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC: <quic_ztu@...cinc.com>, Matti Moell <Matti.Moell@...nsynergy.com>,
        "Mikhail Golubev" <Mikhail.Golubev@...nsynergy.com>
Subject: Re: [PATCH v2 3/3] virtio-spi: Add virtio SPI driver.

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@...13000 {
         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;
> +}
> +