Re: [PATCH v3 1/4] Bluetooth: hci_qca: use wait_until_sent() for power pulses

[Balakrishna Godavarthi]

Hi Johan,

On 2018-12-05 11:55, Johan Hovold wrote:
> On Fri, Nov 30, 2018 at 08:32:44PM +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@xxxxxxxxxxxxxx>
> > ---
> > v3:
> >   * no change.
> > v2:
> >   * Updated function qca_send_power_pulse()
> >   * addressed reviewer comments.
>
> Please make sure to include reviewers on CC when resending, and as
> someone else already mentioned, be a bit more specific about what
> changes you actually made in response to the review feedback you
> received.

[Bala]: sure will add and provide more info in version change history.

> > v1:
> >  * initial patch
> > ---
> >  drivers/bluetooth/hci_qca.c | 37 
> > +++++++++++++------------------------
> >  1 file changed, 13 insertions(+), 24 deletions(-)
> >
> > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> > index f036c8f98ea3..f5dd323c1967 100644
> > --- a/drivers/bluetooth/hci_qca.c
> > +++ b/drivers/bluetooth/hci_qca.c
> > @@ -1013,11 +1013,9 @@ static inline void host_set_baudrate(struct 
> > hci_uart *hu, unsigned int speed)
> >  		hci_uart_set_baudrate(hu, speed);
> >  }
> >
> > -static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
> > +static int qca_send_power_pulse(struct hci_uart *hu, 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
> > @@ -1029,19 +1027,16 @@ static int qca_send_power_pulse(struct hci_dev 
> > *hdev, u8 cmd)
> >  	 * save power. Disabling hardware flow control is mandatory while
> >  	 * 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;
> > -
> > +	bt_dev_dbg(hu->hdev, "sending power pulse %02x to SoC", cmd);
> >  	hci_uart_set_flow_control(hu, true);
> > +	ret = serdev_device_write(hu->serdev, &cmd, sizeof(cmd), 0);
>
> You're still using 0 as a timeout here which is broken, as I already
> told you.

[Bala]: got the change now will update to timeout to non zero value.

> From 4.21 this will result in an indefinite timeout, but currently
> implies not to wait for a full write buffer to drain at all.
>
> As I also mentioned, you need to to make sure to call
> serdev_device_write_wakeup() in the write_wakup() path if you are going
> to use serdev_device_write() at all.

[Bala]: this where i am confused.
        calling serdev_device_write is calling an wakeup internally. 
below is the flow

        ttyport_write_buf:
              * calling serdev_device_write() will call write_buf() in 
this call we are enabling bit "TTY_DO_WRITE_WAKEUP" and calling write()
                i.e. uart_write() where we call in start_tx. this will 
go to the vendor specific write where in isr we call uart_write_wakeup()
                
https://elixir.bootlin.com/linux/latest/source/drivers/tty/serial/qcom_geni_serial.c#L756

        
uart_write_wakeup()->ttyport_write_wakeup()->serdev_controller_write_wakeup()->hci_uart_write_wakeup()->hci_uart_tx_wakeup()

        the above is flow when serdev_device_write() is called, it is 
indirectly calling serdev_write_wakeup().

        Why actual we need to call an serdev_write_wakeup() is this 
wakeup related to the UART port or for the BT chip.

> Johan

--
Regards
Balakrishna.