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

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Message-ID:
 <DB9PR04MB842939900805C080F2CC32B2924C2@DB9PR04MB8429.eurprd04.prod.outlook.com>
Date: Tue, 22 Oct 2024 05:13:25 +0000
From: Sherry Sun <sherry.sun@....com>
To: Marco Felsch <m.felsch@...gutronix.de>
CC: POPESCU Catalin <catalin.popescu@...ca-geosystems.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>,
	Krzysztof Kozlowski <krzk@...nel.org>
Subject: RE: [PATCH 1/2] dt-bindings: net: bluetooth: nxp: add support for
 supply and reset



> -----Original Message-----
> From: Marco Felsch <m.felsch@...gutronix.de>
> Sent: Monday, October 21, 2024 6:26 PM
> 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;
> luiz.dentz@...il.com; robh@...nel.org; krzk+dt@...nel.org;
> conor+dt@...nel.org; p.zabel@...gutronix.de; linux-
> bluetooth@...r.kernel.org; devicetree@...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 24-10-21, Krzysztof Kozlowski wrote:
> > 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.
> 
> I know that DT abstracts the HW. That said I don't see the problem with this
> patch. The HW is abstracted just fine:
> 
> shared PDn          -> reset-gpios
> shared power-supply -> vcc-supply
> 

Actually we should use vcc-supply to control the PDn pin, this is the power supply for NXP wifi/BT.

Best Regards
Sherry