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Date:   Mon, 28 Jan 2019 09:47:50 -0800
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Balakrishna Godavarthi <bgodavar@codeaurora.org>
Cc:     marcel@holtmann.org, johan.hedberg@gmail.com, johan@kernel.org,
        linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org,
        hemantg@codeaurora.org, linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH v9 1/3] Bluetooth: hci_qca: use wait_until_sent() for
 power pulses
Message-ID: <20190128174750.GG81583@google.com>
References: <20190124120808.8275-1-bgodavar@codeaurora.org>
 <20190124120808.8275-2-bgodavar@codeaurora.org>
 <20190125011412.GE81583@google.com>
 <0fac93a13ee445569659075cf467ad4d@codeaurora.org>
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On Mon, Jan 28, 2019 at 07:19:56PM +0530, Balakrishna Godavarthi wrote:
> Hi Matthias,
> 
> On 2019-01-25 06:44, Matthias Kaehlcke wrote:
> > On Thu, Jan 24, 2019 at 05:38:06PM +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>
> > > ---
> > > Changes in v9:
> > >  * Reverted to 100us sleep.
> > >  * used inline call msecs_to_jiffies()
> > > 
> > > Changes in v8:
> > >  * Updated 1 second timeout instead of indefinite wait.
> > > 
> > > Changes in v7:
> > >  *  updated the wait time to 5 ms after sending power pulses.
> > > 
> > > Changes in v6:
> > >  * added serdev_device_write_flush() in qca_send_power_pulse
> > >    instead during the power off pulse.
> > > 
> > > Changes in v5:
> > >  * added serdev_device_write_flush() in qca_power_off().
> > > ---
> > >  drivers/bluetooth/hci_qca.c | 40
> > > +++++++++++++++----------------------
> > >  1 file changed, 16 insertions(+), 24 deletions(-)
> > > 
> > > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> > > index f036c8f98ea3..c08f4d105e73 100644
> > > --- a/drivers/bluetooth/hci_qca.c
> > > +++ b/drivers/bluetooth/hci_qca.c
> > > @@ -60,6 +60,7 @@
> > >  #define IBS_WAKE_RETRANS_TIMEOUT_MS	100
> > >  #define IBS_TX_IDLE_TIMEOUT_MS		2000
> > >  #define BAUDRATE_SETTLE_TIMEOUT_MS	300
> > > +#define POWER_PULSE_TRANS_TIMEOUT_MS	1000
> > 
> > I still doubt that this mega-timeout of 1s is needed, but it shouldn't
> > do any harm either, so whatever ...
> > 
> 
> [Bala]: for now let us have it. we can improve it in the improvement patch
>         based on the results.

Fine.

With the UART buffer flushed and flow control disabled I wonder though
what makes you think that it could take longer than a few milliseconds
for the byte being put on the wire, short of a bug in the UART driver
or hardware, which (if it existed) shouldn't be worked around here.

> > >  /* susclk rate */
> > >  #define SUSCLK_RATE_32KHZ	32768
> > > @@ -1013,11 +1014,10 @@ 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;
> > > +	int timeout = msecs_to_jiffies(POWER_PULSE_TRANS_TIMEOUT_MS);
> > > 
> > >  	/* These power pulses are single byte command which are sent
> > >  	 * at required baudrate to wcn3990. On wcn3990, we have an external
> > > @@ -1029,21 +1029,19 @@ 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 controller", cmd);
> > > 
> > > +	serdev_device_write_flush(hu->serdev);
> > >  	hci_uart_set_flow_control(hu, true);
> > > +	ret = serdev_device_write_buf(hu->serdev, &cmd, sizeof(cmd));
> > > +	if (ret < 0) {
> > > +		bt_dev_err(hu->hdev, "failed to send power pulse %02x", 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, timeout);
> > > 
> > > -	/* Wait for 100 uS for SoC to settle down */
> > > +	/* Wait for 100 uS for SoC to settle down for the received byte. */
> > 
> > I don't think 'for the received byte' adds much value here. If you
> > respin anyway I'd suggest to leave the comment as is.
> > 
> 
> [Bala]: will update.
> 
> > >  	usleep_range(100, 200);
> > >  	hci_uart_set_flow_control(hu, false);
> > > 
> > > @@ -1116,7 +1114,6 @@ static int qca_set_speed(struct hci_uart *hu,
> > > enum qca_speed_type speed_type)
> > > 
> > >  static int qca_wcn3990_init(struct hci_uart *hu)
> > >  {
> > > -	struct hci_dev *hdev = hu->hdev;
> > >  	struct qca_serdev *qcadev;
> > >  	int ret;
> > > 
> > > @@ -1139,12 +1136,12 @@ static int qca_wcn3990_init(struct hci_uart
> > > *hu)
> > > 
> > >  	/* Forcefully enable wcn3990 to enter in to boot mode. */
> > >  	host_set_baudrate(hu, 2400);
> > > -	ret = qca_send_power_pulse(hdev, QCA_WCN3990_POWEROFF_PULSE);
> > > +	ret = qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
> > >  	if (ret)
> > >  		return ret;
> > > 
> > >  	qca_set_speed(hu, QCA_INIT_SPEED);
> > > -	ret = qca_send_power_pulse(hdev, QCA_WCN3990_POWERON_PULSE);
> > > +	ret = qca_send_power_pulse(hu, QCA_WCN3990_POWERON_PULSE);
> > >  	if (ret)
> > >  		return ret;
> > > 
> > > @@ -1274,13 +1271,8 @@ static const struct qca_vreg_data
> > > qca_soc_data = {
> > > 
> > >  static void qca_power_shutdown(struct hci_uart *hu)
> > >  {
> > > -	struct serdev_device *serdev = hu->serdev;
> > > -	unsigned char cmd = QCA_WCN3990_POWEROFF_PULSE;
> > > -
> > >  	host_set_baudrate(hu, 2400);
> > > -	hci_uart_set_flow_control(hu, true);
> > > -	serdev_device_write_buf(serdev, &cmd, sizeof(cmd));
> > > -	hci_uart_set_flow_control(hu, false);
> > > +	qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
> > >  	qca_power_setup(hu, false);
> > >  }
> > > 
> > 
> > Looks good to me besides possible minor improvements:
> > 
> > Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
>