Re: [PATCH 2/3] reset: Add Apple SoC CIO reset driver

["Joshua Peisach" <jpeisach@ubuntu.com>]

On Sun Aug 9, 2026 at 8:16 AM EDT, Sven Peter wrote:
> Add a driver for the reset of the CIO (USB4/Thunderbolt) blocks on
> Apple Silicon SoCs which has to be deasserted before their
> co-processor can be booted. On t8103 each port comes with a dedicated
> register page while t600x uses a single register with one request bit
> per port shared by all ports of a die inside the PMGR MMIO region.
>
> Signed-off-by: Sven Peter <sven@kernel.org>
> ---
>  MAINTAINERS                     |   1 +
>  drivers/reset/Kconfig           |  10 +++
>  drivers/reset/Makefile          |   1 +
>  drivers/reset/reset-apple-cio.c | 182 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 194 insertions(+)

> +
> +static int apple_cio_reset_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct apple_cio_reset *priv;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->variant = of_device_get_match_data(dev);

Might be a dumb question, but does priv->variant also need to be
checked? Because later priv->variant->pmgr_child is and I *think*
it could return NULL.

(Or is this not necessary since in theory the device should only run
this if detected... so this should never be an issue?)

> +
> +	ret = devm_mutex_init(dev, &priv->lock);
> +	if (ret)
> +		return ret;
> +
> +	if (priv->variant->pmgr_child) {
> +		priv->regmap = syscon_node_to_regmap(dev->of_node->parent);
> +		if (IS_ERR(priv->regmap))
> +			return dev_err_probe(dev, PTR_ERR(priv->regmap),
> +					     "Failed to get parent regmap");
> +
> +		ret = of_property_read_u32(dev->of_node, "reg", &priv->offset);
> +		if (ret)
> +			return dev_err_probe(dev, ret, "Failed to read reg offset");
> +	} else {
> +		void __iomem *base;
> +
> +		base = devm_platform_ioremap_resource(pdev, 0);
> +		if (IS_ERR(base))
> +			return PTR_ERR(base);
> +
> +		priv->regmap = devm_regmap_init_mmio(dev, base,
> +						     &apple_cio_reset_regmap_config);
> +		if (IS_ERR(priv->regmap))
> +			return dev_err_probe(dev, PTR_ERR(priv->regmap),
> +					     "Failed to init MMIO regmap");
> +	}
> +
> +	priv->rcdev.owner = THIS_MODULE;
> +	priv->rcdev.ops = &apple_cio_reset_ops;
> +	priv->rcdev.of_node = dev->of_node;
> +	priv->rcdev.nr_resets = priv->variant->nr_resets;
> +
> +	return devm_reset_controller_register(dev, &priv->rcdev);
> +}
> +
> +static const struct of_device_id apple_cio_reset_match[] = {
> +	{
> +		.compatible = "apple,t8103-cio-reset",
> +		.data = &apple_t8103_cio_reset,
> +	},
> +	{
> +		.compatible = "apple,t6000-cio-reset",
> +		.data = &apple_t6000_cio_reset,
> +	},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, apple_cio_reset_match);
> +
> +static struct platform_driver apple_cio_reset_driver = {
> +	.driver = {
> +		.name = "apple-cio-reset",
> +		.of_match_table = apple_cio_reset_match,
> +	},
> +	.probe = apple_cio_reset_probe,
> +};
> +module_platform_driver(apple_cio_reset_driver);
> +
> +MODULE_AUTHOR("Sven Peter <sven@kernel.org>");
> +MODULE_DESCRIPTION("Apple SoC CIO block reset driver");
> +MODULE_LICENSE("Dual MIT/GPL");