Message-ID: <bb34f4ae-92b3-48b7-b0d6-5937756cdbb9@kernel.org>
Date: Mon, 21 Oct 2024 09:50:42 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Marco Felsch <m.felsch@...gutronix.de>
Cc: POPESCU Catalin <catalin.popescu@...ca-geosystems.com>,
 Sherry Sun <sherry.sun@....com>, Amitkumar Karwar
 <amitkumar.karwar@....com>, Neeraj Sanjay Kale <neeraj.sanjaykale@....com>,
 "marcel@...tmann.org" <marcel@...tmann.org>,
 "luiz.dentz@...il.com" <luiz.dentz@...il.com>,
 "robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
 <krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
 "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 GEO-CHHER-bsp-development <bsp-development.geo@...ca-geosystems.com>
Subject: Re: [PATCH 1/2] dt-bindings: net: bluetooth: nxp: add support for
 supply and reset

On 21/10/2024 08:41, Marco Felsch wrote:
> On 24-10-07, Krzysztof Kozlowski wrote:
>> On 07/10/2024 14:58, POPESCU Catalin wrote:
>>>>>>
>>>>>> +  vcc-supply:
>>>>>> +    description:
>>>>>> +      phandle of the regulator that provides the supply voltage.
>>>>>> +
>>>>>> +  reset-gpios:
>>>>>> +    description:
>>>>>> +      Chip powerdown/reset signal (PDn).
>>>>>> +
>>>>> Hi Catalin,
>>>>>
>>>>> For NXP WIFI/BT chip, WIFI and BT share the one PDn pin, which means that both wifi and BT controller will be powered on and off at the same time.
>>>>> Taking the M.2 NXP WIFI/BT module as an example, pin56(W_DISABLE1) is connected to the WIFI/BT chip PDn pin, we has already controlled this pin in the corresponding PCIe/SDIO controller dts nodes.
>>>>> It is not clear to me what exactly pins for vcc-supply and reset-gpios you describing here. Can you help understand the corresponding pins on M.2 interface as an example? Thanks.
>>>
>>> Hi Sherry,
>>>
>>> Regulators and reset controls being refcounted, we can then implement 
>>> powerup sequence in both bluetooth/wlan drivers and have the drivers 
>>> operate independently. This way bluetooth driver would has no dependance 
>>> on the wlan driver for :
>>>
>>> - its power supply
>>>
>>> - its reset pin (PDn)
>>>
>>> - its firmware (being downloaded as part of the combo firmware)
>>>
>>> For the wlan driver we use mmc power sequence to drive the chip reset 
>>> pin and there's another patchset that adds support for reset control 
>>> into the mmc pwrseq simple driver.
>>>
>>>> Please wrap your replies.
>>>>
>>>> It seems you need power sequencing just like Bartosz did for Qualcomm WCN.
>>>
>>> Hi Krzysztof,
>>>
>>> I'm not familiar with power sequencing, but looks like way more 
>>> complicated than reset controls. So, why power sequencing is recommended 
>>> here ? Is it b/c a supply is involved ?
>>
>> Based on earlier message:
>>
>> "For NXP WIFI/BT chip, WIFI and BT share the one PDn pin, which means
>> that both wifi and BT controller will be powered on and off at the same
>> time."
>>
>> but maybe that's not needed. No clue, I don't know the hardware. But be
>> carefully what you write in the bindings, because then it will be ABI.
> 
> We noticed the new power-sequencing infrastructure which is part of 6.11
> too but I don't think that this patch is wrong. The DT ABI won't break
> if we switch to the power-sequencing later on since the "reset-gpios"
> are not marked as required. So it is up to the driver to handle it
> either via a separate power-sequence driver or via "power-supply" and
> "reset-gpios" directly.

That's not the point. We expect correct hardware description. If you say
now it has "reset-gpios" but later say "actually no, because it has
PMU", I respond: no. Describe the hardware, not current Linux.

Best regards,
Krzysztof

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