linux-kernel - Re: [PATCH v1 2/2] Bluetooth: btnxpuart: Add support for 4M baudrate

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Message-ID:
 <AS4PR04MB96927A0C132F5C9404AF2C8AE773A@AS4PR04MB9692.eurprd04.prod.outlook.com>
Date: Tue, 17 Jun 2025 09:57:50 +0000
From: Neeraj Sanjay Kale <neeraj.sanjaykale@....com>
To: Krzysztof Kozlowski <krzk@...nel.org>, Sherry Sun <sherry.sun@....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>
CC: "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>, Manjeet Gupta <manjeet.gupta@....com>
Subject: Re: [PATCH v1 2/2] Bluetooth: btnxpuart: Add support for 4M baudrate

Hi Sherry, Krzysztof,

Thank you for reviewing the patch.

I did not add 4M baudrate support in nxp_recv_fw_req_v1() as V1 bootloader are Legacy chipsets, and 4M baudrate was never tested or used by any customer so far. This feature is more actively used with newer V3 bootloaders. But in my testing w8987 (v1 bootloader) on iMX8M mini works fine at 4M baudrate. I can add it here.

> On 17/06/2025 04:53, Sherry Sun wrote:
> >> @@ -992,7 +997,7 @@ static int nxp_recv_fw_req_v1(struct hci_dev
> >> *hdev, struct sk_buff *skb)
> >>                      nxpdev->helper_downloaded = true;
> >>                      serdev_device_wait_until_sent(nxpdev->serdev, 0);
> >>                      serdev_device_set_baudrate(nxpdev->serdev,
> >> -                                               HCI_NXP_SEC_BAUDRATE);
> >> +
> >> HCI_NXP_SEC_BAUDRATE_3M);
> >
> > Hi Neeraj,
> >
> > Does this mean that some legacy BT chips using nxp_recv_fw_req_v1() don't
> support 4Mbps?
> > If so, please add comments in the commit message.
> 
> If that's true this is implied by compatible and entire property should be
> dropped.
 
As for the code snippet above, it comes into picture for w8997, which needs a helper.bin file to be downloaded before the actual FW file.
The helper.bin sets the chip's baudrate to 3M only, hence I have kept HCI_NXP_SEC_BAUDRATE_3M.

Thanks,
Neeraj