linux-kernel - Re: [PATCH v2 1/2] dt-bindings: net: bluetooth: nxp: Add support for 4M baudrate

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Message-ID:
 <AS4PR04MB9692263405F56AD71E369110E772A@AS4PR04MB9692.eurprd04.prod.outlook.com>
Date: Wed, 18 Jun 2025 15:11:11 +0000
From: Neeraj Sanjay Kale <neeraj.sanjaykale@....com>
To: Paul Menzel <pmenzel@...gen.mpg.de>
CC: "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>, "linux-bluetooth@...r.kernel.org"
	<linux-bluetooth@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, Amitkumar Karwar <amitkumar.karwar@....com>,
	Sherry Sun <sherry.sun@....com>, Manjeet Gupta <manjeet.gupta@....com>
Subject: Re: [PATCH v2 1/2] dt-bindings: net: bluetooth: nxp: Add support for
 4M baudrate

Hi Paul,

Thank you for reviewing this patch.
> 
> Am 18.06.25 um 16:20 schrieb Neeraj Sanjay Kale:
> > Add support for 4000000 as secondary baudrate.
> 
> Could you specify how you tested this, that means, how did you set the
> speed, and then do the test, that it actually works at that speed.

The driver starts at fw-init-baudrate, and if this 'max-speed' baudrate is different, it sends a vendor command to the FW to switch to max-speed.
After this point, both driver and chip communicate over 4000000 baudrate.

I have verified this using Saleae Logic Analyzer, where we have to set the baudrate to decode the UART packets properly. 

I can add these details in V3 driver patch.

> 
> > Signed-off-by: Neeraj Sanjay Kale <neeraj.sanjaykale@....com>
> > ---
> > v2: Use the available 'max-speed' device tree property. (Krzysztof)
> > ---
> >   .../devicetree/bindings/net/bluetooth/nxp,88w8987-bt.yaml  | 7 +++++++
> >   1 file changed, 7 insertions(+)
> >
> > diff --git
> > a/Documentation/devicetree/bindings/net/bluetooth/nxp,88w8987-bt.yaml
> > b/Documentation/devicetree/bindings/net/bluetooth/nxp,88w8987-bt.yaml
> > index 3ab60c70286f..4a1b6ea48a2f 100644
> > ---
> > a/Documentation/devicetree/bindings/net/bluetooth/nxp,88w8987-bt.yaml
> > +++ b/Documentation/devicetree/bindings/net/bluetooth/nxp,88w8987-bt.y
> > +++ aml
> > @@ -34,6 +34,12 @@ properties:
> >         This property depends on the module vendor's
> >         configuration.
> >
> > +  max-speed:
> > +    enum:
> > +      - 3000000
> > +      - 4000000
> > +    default: 3000000
> > +
> >     firmware-name:
> >       maxItems: 1
> >
> > @@ -78,6 +84,7 @@ examples:
> >           bluetooth {
> >               compatible = "nxp,88w8987-bt";
> >               fw-init-baudrate = <3000000>;
> > +            max-speed = <4000000>;
> >               firmware-name = "uartuart8987_bt_v0.bin";
> >               device-wakeup-gpios = <&gpio 11 GPIO_ACTIVE_HIGH>;
> >               nxp,wakein-pin = /bits/ 8 <18>;

Thanks,
Neeraj