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

[Sven Peter <sven@kernel.org>]

On 09.08.26 16:30, Joshua Peisach wrote:
> 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?)

You might be able to get this driver to probe without a device tree node 
by manually forcing it with sysfs but well... play stupid games, win 
stupid prizes.
Adding the check is just two lines and doesn't hurt though.



Best,


Sven