linux-kernel - Re: [PATCH v1] Bluetooth: btnxpuart: Enable flow control before checking boot signature

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Date:   Wed, 19 Apr 2023 12:33:28 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Neeraj Sanjay Kale <neeraj.sanjaykale@....com>
Cc:     marcel@...tmann.org, johan.hedberg@...il.com, luiz.dentz@...il.com,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        amitkumar.karwar@....com, rohit.fule@....com, sherry.sun@....com
Subject: Re: [PATCH v1] Bluetooth: btnxpuart: Enable flow control before
 checking boot signature

Dear Neeraj,


Thank you for your patch.

Am 19.04.23 um 11:03 schrieb Neeraj Sanjay Kale:
> This enables flow control before checking for bootloader signature and
> deciding whether FW download is needed or not. In case of V1 bootloader
> chips w8987 and w8997, it is observed that if WLAN FW is downloaded first
> and power save is enabled in wlan core, bootloader signatures are not
> emitted by the BT core when the chip is put to sleep. This results in BT
> FW download timeout error.

If there is a log message, maybe paste it.

> By enabling the flow control, the host enables
> its RTS pin, and an interrupt in chip's UART peripheral causes the
> bootloader to wakeup, enabling the bootloader signatures, which then helps

Nit: The verb wake up is spelled with a space.

> in downloading the bluetooth FW file.
> 
> Signed-off-by: Neeraj Sanjay Kale <neeraj.sanjaykale@....com>
> ---
>   drivers/bluetooth/btnxpuart.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/bluetooth/btnxpuart.c b/drivers/bluetooth/btnxpuart.c
> index 93f3afc0c0c8..3ee41a0d45e7 100644
> --- a/drivers/bluetooth/btnxpuart.c
> +++ b/drivers/bluetooth/btnxpuart.c
> @@ -967,7 +967,7 @@ static int nxp_set_ind_reset(struct hci_dev *hdev, void *data)
>   static int nxp_check_boot_sign(struct btnxpuart_dev *nxpdev)
>   {
>   	serdev_device_set_baudrate(nxpdev->serdev, HCI_NXP_PRI_BAUDRATE);
> -	serdev_device_set_flow_control(nxpdev->serdev, 0);
> +	serdev_device_set_flow_control(nxpdev->serdev, 1);

It was explicitly disabled before. Is it on by default?

Also, is there now a redundant line later in the flow enabling flow 
control, or was it never enabled?

Other place in the source code seem to use `true` or `false` instead of 1/0.

>   	set_bit(BTNXPUART_CHECK_BOOT_SIGNATURE, &nxpdev->tx_state);
>   
>   	return wait_event_interruptible_timeout(nxpdev->check_boot_sign_wait_q,


Kind regards,

Paul