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

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Message-ID: <20241021064129.trchqa2oickna7pc@pengutronix.de>
Date: Mon, 21 Oct 2024 08:41:29 +0200
From: Marco Felsch <m.felsch@...gutronix.de>
To: Krzysztof Kozlowski <krzk@...nel.org>
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 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.

Regards,
  Marco

> Best regards,
> Krzysztof
> 
>