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SubjectRe: [PATCH v1 1/4] Bluetooth: hci_qca: use wait_until_sent() for power pulses
On Tue, Nov 06, 2018 at 05:35:25PM +0530, Balakrishna Godavarthi wrote:
> wcn3990 requires a power pulse to turn ON/OFF along with
> regulators. Sometimes we are observing the power pulses are sent
> out with some time delay, due to queuing these commands. This is
> causing synchronization issues with chip, which intern delay the
> chip setup or may end up with communication issues.
>
> Signed-off-by: Balakrishna Godavarthi <bgodavar@codeaurora.org>
> ---
> drivers/bluetooth/hci_qca.c | 22 +++++++++-------------
> 1 file changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index f72ded4ec9ae..051f081d1835 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -1016,8 +1016,7 @@ static inline void host_set_baudrate(struct hci_uart *hu, unsigned int speed)
> static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
> {
> struct hci_uart *hu = hci_get_drvdata(hdev);
> - struct qca_data *qca = hu->priv;
> - struct sk_buff *skb;
> + int ret;
>
> /* These power pulses are single byte command which are sent
> * at required baudrate to wcn3990. On wcn3990, we have an external
> @@ -1030,18 +1029,14 @@ static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
> * sending power pulses to SoC.
> */
> bt_dev_dbg(hdev, "sending power pulse %02x to SoC", cmd);
> -
> - skb = bt_skb_alloc(sizeof(cmd), GFP_KERNEL);
> - if (!skb)
> - return -ENOMEM;
> -
> hci_uart_set_flow_control(hu, true);
> + ret = serdev_device_write(hu->serdev, &cmd, sizeof(cmd), 0);
> + if (ret < 0) {
> + bt_dev_err(hdev, "failed to send power pulse %02x to SoC", cmd);
> + return ret;
> + }
>
> - skb_put_u8(skb, cmd);
> - hci_skb_pkt_type(skb) = HCI_COMMAND_PKT;
> -
> - skb_queue_tail(&qca->txq, skb);
> - hci_uart_tx_wakeup(hu);
> + serdev_device_wait_until_sent(hu->serdev, 0);
>
> /* Wait for 100 uS for SoC to settle down */
> usleep_range(100, 200);

Is the delay still needed now that we wait for the pulse to be sent? I
didn't observe any problems without it in a few dozens of iterations.

> @@ -1283,7 +1278,8 @@ static void qca_power_shutdown(struct hci_uart *hu)
>
> host_set_baudrate(hu, 2400);
> hci_uart_set_flow_control(hu, true);
> - serdev_device_write_buf(serdev, &cmd, sizeof(cmd));
> + serdev_device_write(serdev, &cmd, sizeof(cmd), 0);
> + serdev_device_wait_until_sent(serdev, 0);
> hci_uart_set_flow_control(hu, false);

You could call qca_send_power_pulse(hdev, QCA_WCN3990_POWEROFF_PULSE)
instead, as an earlier patch set did before skbs were used to send the
power pulse.

You can also consider to set the baudrate in qca_send_power_pulse()
depending on the power pulse. On the plus side this would reduce a bit
of clutter in the callers of qca_send_power_pulse(), on the negative
side it would be harder to follow when baudrate changes occur (not
sure this is a problem). Up to you, just an idea.

Thanks

Matthias

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