linux-kernel - Re: [PATCH 1/2] dt-bindings: net: bluetooth: nxp: add support for supply and reset

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Message-ID: <0d460226-4ea7-4a9b-a119-468343727996@kernel.org>
Date: Mon, 7 Oct 2024 16:54:29 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: 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>
Cc: "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>,
 "m.felsch@...gutronix.de" <m.felsch@...gutronix.de>,
 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 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.

Best regards,
Krzysztof