linux-kernel - Re: [PATCH v6 5/6] Bluetooth: hci_qca: Update baudrate change wait time for wcn3990

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Date:   Thu, 27 Dec 2018 13:00:23 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Balakrishna Godavarthi <bgodavar@...eaurora.org>
Cc:     marcel@...tmann.org, johan.hedberg@...il.com,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        hemantg@...eaurora.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v6 5/6] Bluetooth: hci_qca: Update baudrate change wait
 time for wcn3990

On Thu, Dec 27, 2018 at 01:01:35PM +0530, Balakrishna Godavarthi wrote:
> This patch will update the baudrate change request wait time from
> 300 ms to 100 ms. When host sends the change baudrate request to
> the controller, controller sets its clock and wait until the
> clocks settle down. Here the Wait time is required for both
> host and controller to be on sync.

Ultimately up to you, but I would advise against adding 'improvement'
changes to this series. The scope of the series is already fairly
vague ("Bug fixes for Qualcomm BT chip wcn3990"), with at least some
patches that could be sent individually, which would reduce churn when
respinning.

> Signed-off-by: Balakrishna Godavarthi <bgodavar@...eaurora.org>
> ---
> 
> Changes in v6:
>  * intial patch.
> 
> ---
>  drivers/bluetooth/hci_qca.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index 4677a6a2716a..61b0fb1ff32f 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -60,7 +60,8 @@
>  
>  #define IBS_WAKE_RETRANS_TIMEOUT_MS	100
>  #define IBS_TX_IDLE_TIMEOUT_MS		2000
> -#define BAUDRATE_SETTLE_TIMEOUT_MS	300
> +#define ROME_BD_SETTLE_TIMEOUT_MS	300
> +#define WCN3990_BD_SETTLE_TIMEOUT_MS	100

My testing suggests that even the lower 100 ms delay isn't needed, if
different parts that require a delay are addressed more specifically,
instead of using a single long 'settle' delay
(https://lore.kernel.org/patchwork/patch/1026795/#1212816 has some
details).

My idea was to sent a patch after this series has landed to avoid
interfering with it.

Cheers

Matthias