[linux-nfc] Re: [PATCH] NFC: NCI: make parent aware in PM terms

On 23.08.21 13:29, Krzysztof Kozlowski wrote:
> On 23/08/2021 12:50, Oliver Neukum wrote:
>> On 19.08.21 16:45, Krzysztof Kozlowski wrote


Hi,

>> I personally like it a lot because I have filters organized with it.
>> Nowadays no one reads LKML itself (too big volume) so it is purely for
>> archiving on lore.kernel.org for searching and for people's filters.
>>
>> Therefore unless someone here objects, I would prefer to Cc LKML as
>> well. Anyway, netdev is important as it is tracked by patchwork.
very well, It shall be done.
>> As far as I can tell I am doing this for the device noted in nfc_dev.
>> Could you elaborate?
> I meant that it looks unusual that you don't do it for your own device
> (client->dev) but for device allocated in different unit. Here, you
> receive client->dev and mostly you should play only with it.
>
> While I am looking at this more, there is another issue actually - you
> touch runtime PM of NFC/NCI core device but it's the NFC/NCI core who
> should handle it's own runtime PM.

Well, I looked into that and that was very difficult. The NFC core has
no idea what hardware it is running on. On my test hardware as far as
I can tell, the power supply of my NFC hardware is just tied to
the power supply of the i2c host controller, which is a PCI device.

It goes into D3cold when the i2c bus is not transferring anything.
That makes it impossible to actually communicate over NFC.

However, at least on USB sending a device into USB suspend with
remote wakeup should work. So I do not see how to put this into
NFC core.

    Regards
        Oliver
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